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Siri Fjellheim - One of the best experts on this subject based on the ideXlab platform.
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Increased above-ground resource allocation is a likely precursor for independent evolutionary origins of annuality in the Pooideae grass subfamily.
The New phytologist, 2020Co-Authors: Camilla Lorange Lindberg, Marian Schubert, Thomas Marcussen, Ben Trevaskis, Jill C. Preston, Hans Martin Hanslin, Siri FjellheimAbstract:Semelparous annual plants flower a single time during their 1-yr life cycle, investing much of their energy into rapid reproduction. By contrast, iteroparous perennial plants flower multiple times over several years, and partition their resources between reproduction and persistence. To which extent evolutionary transitions between life-cycle strategies are internally constrained at the developmental, genetic and phylogenetic level is unknown. Here we study the evolution of life-cycle strategies in the grass subfamily Pooideae and test if transitions between them are facilitated by evolutionary precursors. We integrate ecological, life-cycle strategy and growth data in a phylogenetic framework. We investigate if growth traits are candidates for a precursor. Species in certain Pooideae clades are predisposed to evolve annuality from perenniality, potentially due to the shared inheritance of specific evolutionary precursors. Seasonal dry climates, which have been linked to annuality, were only able to select for transitions to annuality when the precursor was present. Allocation of more resources to above-ground rather than below-ground growth is a candidate for the precursor. Our findings support the hypothesis that only certain lineages can respond quickly to changing external conditions by switching their life-cycle strategy, likely due to the presence of evolutionary precursors.
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the grass subfamily Pooideae cretaceous palaeocene origin and climate driven cenozoic diversification
Global Ecology and Biogeography, 2019Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:AIM: Frost is among the most dramatic stresses a plant can experience, and complex physiological adaptations are needed to endure long periods of sub‐zero temperatures. Owing to the need to evolve these complex adaptations, transitioning from tropical to temperate climates is regarded as difficult. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates cool temperate, continental and Arctic regions. We produce a dated phylogeny and investigate the role of climate cooling in diversification. LOCATION: Global, temperate regions. TIME PERIOD: Cretaceous–Cenozoic. MAJOR TAXA: Pooideae. METHODS: Using newly available fossils and methods, we dated a comprehensive Pooideae phylogeny and tested for the impact of palaeoclimates on diversification rates. Using ancestral state reconstruction, we investigated whether Pooideae ancestors experienced frost and winter. To locate the ancestral distribution area of Pooideae, we performed biogeographical analyses. RESULTS: We estimated a Late Cretaceous/early Palaeocene origin of the Pooideae (61–77 Ma), with all major clades already having diversified at the Eocene–Oligocene climate cooling (34 Ma). Climate cooling was a probable driving force of Pooideae diversification. Pooideae probably evolved in a temperate niche experiencing frost, but not long winters. MAIN CONCLUSION: Pooideae probably originated in a temperate niche and experienced cold temperatures and frost long before expansion of temperate biomes after the Eocene–Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that certain responses to low‐temperature stress are shared in extant Pooideae grasses. Throughout the Cenozoic, falling temperatures and expansion of temperate biomes were associated with an increase in diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most probably evolved independently in daughter lineages. Our findings provide insight into how adaptations to historical changes in chill and frost exposure influence the distribution of plant diversity today.
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The grass subfamily Pooideae: Cretaceous–Palaeocene origin and climate‐driven Cenozoic diversification
Global Ecology and Biogeography, 2019Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:AIM: Frost is among the most dramatic stresses a plant can experience, and complex physiological adaptations are needed to endure long periods of sub‐zero temperatures. Owing to the need to evolve these complex adaptations, transitioning from tropical to temperate climates is regarded as difficult. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates cool temperate, continental and Arctic regions. We produce a dated phylogeny and investigate the role of climate cooling in diversification. LOCATION: Global, temperate regions. TIME PERIOD: Cretaceous–Cenozoic. MAJOR TAXA: Pooideae. METHODS: Using newly available fossils and methods, we dated a comprehensive Pooideae phylogeny and tested for the impact of palaeoclimates on diversification rates. Using ancestral state reconstruction, we investigated whether Pooideae ancestors experienced frost and winter. To locate the ancestral distribution area of Pooideae, we performed biogeographical analyses. RESULTS: We estimated a Late Cretaceous/early Palaeocene origin of the Pooideae (61–77 Ma), with all major clades already having diversified at the Eocene–Oligocene climate cooling (34 Ma). Climate cooling was a probable driving force of Pooideae diversification. Pooideae probably evolved in a temperate niche experiencing frost, but not long winters. MAIN CONCLUSION: Pooideae probably originated in a temperate niche and experienced cold temperatures and frost long before expansion of temperate biomes after the Eocene–Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that certain responses to low‐temperature stress are shared in extant Pooideae grasses. Throughout the Cenozoic, falling temperatures and expansion of temperate biomes were associated with an increase in diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most probably evolved independently in daughter lineages. Our findings provide insight into how adaptations to historical changes in chill and frost exposure influence the distribution of plant diversity today.
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Evolution of Cold Acclimation and Its Role in Niche Transition in the Temperate Grass Subfamily Pooideae
Plant physiology, 2019Co-Authors: Marian Schubert, Simen Rød Sandve, Lars Groenvold, Torgeir R. Hvidsten, Siri FjellheimAbstract:The grass subfamily Pooideae dominates the grass floras in cold temperate regions and has evolved complex physiological adaptations to cope with extreme environmental conditions like frost, winter, and seasonality. One such adaptation is cold acclimation, wherein plants increase their frost tolerance in response to gradually falling temperatures and shorter days in the autumn. However, understanding how complex traits like cold acclimation evolve remains a major challenge in evolutionary biology. Here, we investigated the evolution of cold acclimation in Pooideae and found that a phylogenetically diverse set of Pooideae species displayed cold acclimation capacity. However, comparing differential gene expression after cold treatment in transcriptomes of five phylogenetically diverse species revealed widespread species-specific responses of genes with conserved sequences. Furthermore, we studied the correlation between gene family size and number of cold-responsive genes as well as between selection pressure on coding sequences of genes and their cold responsiveness. We saw evidence of protein-coding and regulatory sequence evolution as well as the origin of novel genes and functions contributing toward evolution of a cold response in Pooideae. Our results reflect that selection pressure resulting from global cooling must have acted on already diverged lineages. Nevertheless, conservation of cold-induced gene expression of certain genes indicates that the Pooideae ancestor may have possessed some molecular machinery to mitigate cold stress. Evolution of adaptations to seasonally cold climates is regarded as particularly difficult. How Pooideae evolved to transition from tropical to temperate biomes sheds light on how complex traits evolve in the light of climate changes.
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The grass subfamily Pooideae: late Cretaceous origin and climate-driven Cenozoic diversification
2018Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:Aim: Frost is among the most dramatic stresses a plant can experience and complex physiological adaptations are needed to endure long periods of sub-zero temperatures. Due to the need for evolving these complex adaptations, transitioning from tropical to temperate climates is regarded difficult and only half of the world9s seed plant families have temperate representatives. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates the northern temperate grass floras. Specifically, we investigate the role of climate cooling in diversification. Location: Global, temperate regions Time period: Late Cretaceous-Cenozoic Major taxa: The grass subfamily Pooideae Methods: We date a comprehensive Pooideae phylogeny and test for the impact of paleoclimates on diversification rates. Using ancestral state reconstruction, we investigate if Pooideae ancestors experienced frost and winter. To locate the area of origin of Pooideae we perform biogeographical analyses. Results: We estimated a late Cretaceous origin of the Pooideae (66 million years ago (Mya)), and all major clades had already diversified at the Eocene-Oligocene transition climate cooling (34 Mya). Climate cooling was a probable driving force of Pooideae diversification. Pooideae likely evolved in mountainous regions of southwestern Eurasia in a temperate niche experiencing frost, but not long winters. Main conclusion: Pooideae originated in a temperate niche and experienced cold temperatures and frost long before the expansion of temperate biomes after the Eocene-Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that extant Pooideae grasses share responses to low temperature stress in Pooideae. Throughout the Cenozoic falling temperatures triggered diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most likely evolved independently in lower taxonomic lineages. Our findings provide insight into how adaptations to historic changes in chill and frost exposure influence distribution of plant diversity today.
Marian Schubert - One of the best experts on this subject based on the ideXlab platform.
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Increased above-ground resource allocation is a likely precursor for independent evolutionary origins of annuality in the Pooideae grass subfamily.
The New phytologist, 2020Co-Authors: Camilla Lorange Lindberg, Marian Schubert, Thomas Marcussen, Ben Trevaskis, Jill C. Preston, Hans Martin Hanslin, Siri FjellheimAbstract:Semelparous annual plants flower a single time during their 1-yr life cycle, investing much of their energy into rapid reproduction. By contrast, iteroparous perennial plants flower multiple times over several years, and partition their resources between reproduction and persistence. To which extent evolutionary transitions between life-cycle strategies are internally constrained at the developmental, genetic and phylogenetic level is unknown. Here we study the evolution of life-cycle strategies in the grass subfamily Pooideae and test if transitions between them are facilitated by evolutionary precursors. We integrate ecological, life-cycle strategy and growth data in a phylogenetic framework. We investigate if growth traits are candidates for a precursor. Species in certain Pooideae clades are predisposed to evolve annuality from perenniality, potentially due to the shared inheritance of specific evolutionary precursors. Seasonal dry climates, which have been linked to annuality, were only able to select for transitions to annuality when the precursor was present. Allocation of more resources to above-ground rather than below-ground growth is a candidate for the precursor. Our findings support the hypothesis that only certain lineages can respond quickly to changing external conditions by switching their life-cycle strategy, likely due to the presence of evolutionary precursors.
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the grass subfamily Pooideae cretaceous palaeocene origin and climate driven cenozoic diversification
Global Ecology and Biogeography, 2019Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:AIM: Frost is among the most dramatic stresses a plant can experience, and complex physiological adaptations are needed to endure long periods of sub‐zero temperatures. Owing to the need to evolve these complex adaptations, transitioning from tropical to temperate climates is regarded as difficult. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates cool temperate, continental and Arctic regions. We produce a dated phylogeny and investigate the role of climate cooling in diversification. LOCATION: Global, temperate regions. TIME PERIOD: Cretaceous–Cenozoic. MAJOR TAXA: Pooideae. METHODS: Using newly available fossils and methods, we dated a comprehensive Pooideae phylogeny and tested for the impact of palaeoclimates on diversification rates. Using ancestral state reconstruction, we investigated whether Pooideae ancestors experienced frost and winter. To locate the ancestral distribution area of Pooideae, we performed biogeographical analyses. RESULTS: We estimated a Late Cretaceous/early Palaeocene origin of the Pooideae (61–77 Ma), with all major clades already having diversified at the Eocene–Oligocene climate cooling (34 Ma). Climate cooling was a probable driving force of Pooideae diversification. Pooideae probably evolved in a temperate niche experiencing frost, but not long winters. MAIN CONCLUSION: Pooideae probably originated in a temperate niche and experienced cold temperatures and frost long before expansion of temperate biomes after the Eocene–Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that certain responses to low‐temperature stress are shared in extant Pooideae grasses. Throughout the Cenozoic, falling temperatures and expansion of temperate biomes were associated with an increase in diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most probably evolved independently in daughter lineages. Our findings provide insight into how adaptations to historical changes in chill and frost exposure influence the distribution of plant diversity today.
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The grass subfamily Pooideae: Cretaceous–Palaeocene origin and climate‐driven Cenozoic diversification
Global Ecology and Biogeography, 2019Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:AIM: Frost is among the most dramatic stresses a plant can experience, and complex physiological adaptations are needed to endure long periods of sub‐zero temperatures. Owing to the need to evolve these complex adaptations, transitioning from tropical to temperate climates is regarded as difficult. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates cool temperate, continental and Arctic regions. We produce a dated phylogeny and investigate the role of climate cooling in diversification. LOCATION: Global, temperate regions. TIME PERIOD: Cretaceous–Cenozoic. MAJOR TAXA: Pooideae. METHODS: Using newly available fossils and methods, we dated a comprehensive Pooideae phylogeny and tested for the impact of palaeoclimates on diversification rates. Using ancestral state reconstruction, we investigated whether Pooideae ancestors experienced frost and winter. To locate the ancestral distribution area of Pooideae, we performed biogeographical analyses. RESULTS: We estimated a Late Cretaceous/early Palaeocene origin of the Pooideae (61–77 Ma), with all major clades already having diversified at the Eocene–Oligocene climate cooling (34 Ma). Climate cooling was a probable driving force of Pooideae diversification. Pooideae probably evolved in a temperate niche experiencing frost, but not long winters. MAIN CONCLUSION: Pooideae probably originated in a temperate niche and experienced cold temperatures and frost long before expansion of temperate biomes after the Eocene–Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that certain responses to low‐temperature stress are shared in extant Pooideae grasses. Throughout the Cenozoic, falling temperatures and expansion of temperate biomes were associated with an increase in diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most probably evolved independently in daughter lineages. Our findings provide insight into how adaptations to historical changes in chill and frost exposure influence the distribution of plant diversity today.
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Evolution of Cold Acclimation and Its Role in Niche Transition in the Temperate Grass Subfamily Pooideae
Plant physiology, 2019Co-Authors: Marian Schubert, Simen Rød Sandve, Lars Groenvold, Torgeir R. Hvidsten, Siri FjellheimAbstract:The grass subfamily Pooideae dominates the grass floras in cold temperate regions and has evolved complex physiological adaptations to cope with extreme environmental conditions like frost, winter, and seasonality. One such adaptation is cold acclimation, wherein plants increase their frost tolerance in response to gradually falling temperatures and shorter days in the autumn. However, understanding how complex traits like cold acclimation evolve remains a major challenge in evolutionary biology. Here, we investigated the evolution of cold acclimation in Pooideae and found that a phylogenetically diverse set of Pooideae species displayed cold acclimation capacity. However, comparing differential gene expression after cold treatment in transcriptomes of five phylogenetically diverse species revealed widespread species-specific responses of genes with conserved sequences. Furthermore, we studied the correlation between gene family size and number of cold-responsive genes as well as between selection pressure on coding sequences of genes and their cold responsiveness. We saw evidence of protein-coding and regulatory sequence evolution as well as the origin of novel genes and functions contributing toward evolution of a cold response in Pooideae. Our results reflect that selection pressure resulting from global cooling must have acted on already diverged lineages. Nevertheless, conservation of cold-induced gene expression of certain genes indicates that the Pooideae ancestor may have possessed some molecular machinery to mitigate cold stress. Evolution of adaptations to seasonally cold climates is regarded as particularly difficult. How Pooideae evolved to transition from tropical to temperate biomes sheds light on how complex traits evolve in the light of climate changes.
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The grass subfamily Pooideae: late Cretaceous origin and climate-driven Cenozoic diversification
2018Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:Aim: Frost is among the most dramatic stresses a plant can experience and complex physiological adaptations are needed to endure long periods of sub-zero temperatures. Due to the need for evolving these complex adaptations, transitioning from tropical to temperate climates is regarded difficult and only half of the world9s seed plant families have temperate representatives. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates the northern temperate grass floras. Specifically, we investigate the role of climate cooling in diversification. Location: Global, temperate regions Time period: Late Cretaceous-Cenozoic Major taxa: The grass subfamily Pooideae Methods: We date a comprehensive Pooideae phylogeny and test for the impact of paleoclimates on diversification rates. Using ancestral state reconstruction, we investigate if Pooideae ancestors experienced frost and winter. To locate the area of origin of Pooideae we perform biogeographical analyses. Results: We estimated a late Cretaceous origin of the Pooideae (66 million years ago (Mya)), and all major clades had already diversified at the Eocene-Oligocene transition climate cooling (34 Mya). Climate cooling was a probable driving force of Pooideae diversification. Pooideae likely evolved in mountainous regions of southwestern Eurasia in a temperate niche experiencing frost, but not long winters. Main conclusion: Pooideae originated in a temperate niche and experienced cold temperatures and frost long before the expansion of temperate biomes after the Eocene-Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that extant Pooideae grasses share responses to low temperature stress in Pooideae. Throughout the Cenozoic falling temperatures triggered diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most likely evolved independently in lower taxonomic lineages. Our findings provide insight into how adaptations to historic changes in chill and frost exposure influence distribution of plant diversity today.
Jill C. Preston - One of the best experts on this subject based on the ideXlab platform.
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Variation in climatic tolerance, but not stomatal traits, partially explains Pooideae grass species distributions.
Annals of botany, 2021Co-Authors: Aayudh Das, Anoob Prakash, Natalie Dedon, Alex Doty, Muniba Siddiqui, Jill C. PrestonAbstract:Grasses in subfamily Pooideae live in some of the world's harshest terrestrial environments, from frigid boreal zones to the arid wind-swept steppe. It is hypothesized that the climate distribution of species within this group is driven by differences in climatic tolerance, and that tolerance can be partially explained by variation in stomatal traits. We determined aridity index (AI) and minimum temperature of the coldest month (MTCM) for 22 diverse Pooideae accessions and one outgroup, and used comparative methods to assess predicted relationships for climate traits versus fitness traits, stomatal diffusive conductance to water (gw), and speed of stomatal closure following drought and/or cold. Results demonstrate that AI and MTCM predict variation in survival/regreening following drought/cold, and gw under drought/cold is positively correlated with ẟ 13C-measured water use efficiency (WUE). However, the relationship between climate traits and fitness under drought/cold was not explained by gw or speed of stomatal closure. These findings suggest that Pooideae distributions are at least partly determined by tolerance to aridity and above freezing cold, but that variation in tolerance is not uniformly explained by variation in stomatal traits. © The Author(s) 2021. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
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Increased above-ground resource allocation is a likely precursor for independent evolutionary origins of annuality in the Pooideae grass subfamily.
The New phytologist, 2020Co-Authors: Camilla Lorange Lindberg, Marian Schubert, Thomas Marcussen, Ben Trevaskis, Jill C. Preston, Hans Martin Hanslin, Siri FjellheimAbstract:Semelparous annual plants flower a single time during their 1-yr life cycle, investing much of their energy into rapid reproduction. By contrast, iteroparous perennial plants flower multiple times over several years, and partition their resources between reproduction and persistence. To which extent evolutionary transitions between life-cycle strategies are internally constrained at the developmental, genetic and phylogenetic level is unknown. Here we study the evolution of life-cycle strategies in the grass subfamily Pooideae and test if transitions between them are facilitated by evolutionary precursors. We integrate ecological, life-cycle strategy and growth data in a phylogenetic framework. We investigate if growth traits are candidates for a precursor. Species in certain Pooideae clades are predisposed to evolve annuality from perenniality, potentially due to the shared inheritance of specific evolutionary precursors. Seasonal dry climates, which have been linked to annuality, were only able to select for transitions to annuality when the precursor was present. Allocation of more resources to above-ground rather than below-ground growth is a candidate for the precursor. Our findings support the hypothesis that only certain lineages can respond quickly to changing external conditions by switching their life-cycle strategy, likely due to the presence of evolutionary precursors.
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Successive evolutionary steps drove Pooideae grasses from tropical to temperate regions.
The New phytologist, 2017Co-Authors: Jinshun Zhong, Meghan Robbett, Alfonso Poire, Jill C. PrestonAbstract:Angiosperm adaptations to seasonally cold climates have occurred multiple times independently. However, the observation that less than half of all angiosperm families are represented in temperate latitudes suggests internal constraints on the evolution of cold tolerance/avoidance strategies. Similar to angiosperms as a whole, grasses are primarily tropical, but one major clade, subfamily Pooideae, radiated extensively within temperate regions. It is posited that this Pooideae niche transition was facilitated by an early origin of long-term cold responsiveness around the base of the subfamily, and that a set of more ancient pathways enabled evolution of seasonal cold tolerance. To test this, we compared transcriptome-level responses of disparate Pooideae to short-/long-term cold and with those previously known in the subtropical grass rice (Ehrhartoideae). Analyses identified several highly conserved cold-responsive 'orthogroups' within our focal Pooideae species that originated successively during the diversification of land plants, predominantly via gene duplication. The majority of conserved Pooideae cold-responsive genes appear to have ancient roles in stress responses, with most of the orthogroups also being sensitive to cold in rice. However, a subgroup of genes was likely co-opted de novo early in the Pooideae. These results highlight a plausible stepwise evolutionary trajectory for cold adaptations across Pooideae.
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Evolution of the miR5200-FLOWERING LOCUS T flowering time regulon in the temperate grass subfamily Pooideae.
Molecular phylogenetics and evolution, 2017Co-Authors: Meghan Mckeown, Jill C. Preston, Marian Schubert, Siri FjellheimAbstract:Flowering time is a carefully regulated trait controlled primarily through the action of the central genetic regulator, FLOWERING LOCUS T (FT). Recently it was demonstrated that a microRNA, miR5200, targets the end of the second exon of FT under short-day photoperiods in the grass subfamily Pooideae, thus preventing FT transcripts from reaching threshold levels under non-inductive conditions. Pooideae are an interesting group in that they rapidly diversified from the tropics into the northern temperate region during a major global cooling event spanning the Eocene-Oligocene transition. We hypothesize that miR5200 photoperiod-sensitive regulation of Pooideae flowering time networks assisted their transition into northern seasonal environments. Here, we test predictions derived from this hypothesis that miR5200, originally found in bread wheat and later identified in Brachypodium distachyon, (1) was present in the genome of the Pooideae common ancestor, (2) is transcriptionally regulated by photoperiod, and (3) is negatively correlated with FT transcript abundance, indicative of miR5200 regulating FT. Our results demonstrate that miR5200 did evolve at or around the base of Pooideae, but only acquired photoperiod-regulated transcription within the Brachypodium lineage. Based on expression profiles and previous data, we posit that the progenitor of miR5200 was co-regulated with FT by an unknown mechanism.
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Evolution of vernalization response in the PACMAD clade of the grass family (Poaceae)
2017Co-Authors: Martin Paliocha, Jill C. Preston, Marian Schubert, Siri FjellheimAbstract:Vernalization is a physiological process that establishes floral meristem identity in response to prolonged periods of cold. Thereby, production of flowers in overwintering plants is aligned with the onset of spring, synchronizing reproduction with favorable environmental conditions. Proper timing of developmental transitions is crucial to the success of plants in regions with pronounced seasonal variation. Many vernalization systems have evolved in independently in different plant lineages. This allowed the expansion of certain plant groups from their tropical origins into novel habitats at higher latitudes. Due to its significance in agriculture, vernalization mechanisms of species from the mainly temperate grass subfamily Pooideae is well-studied and has been characterized on a molecular level. Recent advances demonstrate that the core regulatory network governing vernalization response is evolutionarily conserved within the Pooideae (McKeown et al. 2016). In this project, we seek to investigate whether this is true for other temperate grass lineages, focusing on species from the monophyletic PACMAD clade comprised of six distinct grass-subfamilies.
Simen Rød Sandve - One of the best experts on this subject based on the ideXlab platform.
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Evolution of Cold Acclimation and Its Role in Niche Transition in the Temperate Grass Subfamily Pooideae
Plant physiology, 2019Co-Authors: Marian Schubert, Simen Rød Sandve, Lars Groenvold, Torgeir R. Hvidsten, Siri FjellheimAbstract:The grass subfamily Pooideae dominates the grass floras in cold temperate regions and has evolved complex physiological adaptations to cope with extreme environmental conditions like frost, winter, and seasonality. One such adaptation is cold acclimation, wherein plants increase their frost tolerance in response to gradually falling temperatures and shorter days in the autumn. However, understanding how complex traits like cold acclimation evolve remains a major challenge in evolutionary biology. Here, we investigated the evolution of cold acclimation in Pooideae and found that a phylogenetically diverse set of Pooideae species displayed cold acclimation capacity. However, comparing differential gene expression after cold treatment in transcriptomes of five phylogenetically diverse species revealed widespread species-specific responses of genes with conserved sequences. Furthermore, we studied the correlation between gene family size and number of cold-responsive genes as well as between selection pressure on coding sequences of genes and their cold responsiveness. We saw evidence of protein-coding and regulatory sequence evolution as well as the origin of novel genes and functions contributing toward evolution of a cold response in Pooideae. Our results reflect that selection pressure resulting from global cooling must have acted on already diverged lineages. Nevertheless, conservation of cold-induced gene expression of certain genes indicates that the Pooideae ancestor may have possessed some molecular machinery to mitigate cold stress. Evolution of adaptations to seasonally cold climates is regarded as particularly difficult. How Pooideae evolved to transition from tropical to temperate biomes sheds light on how complex traits evolve in the light of climate changes.
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Evolution of cold acclimation in temperate grasses (Pooideae)
2017Co-Authors: Marian Schubert, Simen Rød Sandve, Lars Groenvold, Torgeir R. Hvidsten, Siri FjellheimAbstract:In the past 50 million years climate cooling has triggered the expansion of temperate biomes. During this period, many extant plant lineages in temperate biomes evolved from tropical ancestors and adapted to seasonality and cool conditions. Among the Poaceae (grass family), one of the subfamilies that successfully shifted from tropical to temperate biomes is the Pooideae (temperate grasses). Subfamily Pooideae contains the most important crops cultivated in the temperate regions including wheat (Triticum aestivum) and barley (Hordeum vulgare). Due to the need of well-adapted cultivars, extensive research has produced a large body of knowledge about the mechanisms underlying cold adaptation in cultivated Pooideae species. Especially cold acclimation, a process which increases the frost tolerance during a period of non-freezing cold, plays an important role. Because cold adaptation is largely unexplored in lineages that diverged early in the evolution of the Pooideae, little is known about the evolutionary history of cold acclimation in the Pooideae. Here we test if several species of early diverging lineages exhibit increased frost tolerance after a period of cold acclimation. We further investigate the conservation of five well-studied gene families that are known to be involved in the cold acclimation of Pooideae crop species. Our results indicate that cold acclimation exists in early diverging lineages, but that genes involved in regulation of cold acclimation are not conserved. The investigated gene families show signs of lineage-specific evolution and support the hypothesis that gene family expansion is an important mechanism in adaptive evolution.
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comparative transcriptomics provides insight into the evolution of cold response in Pooideae
bioRxiv, 2017Co-Authors: Lars Gronvold, Siri Fjellheim, Marian Schubert, Simen Rød Sandve, Torgeir R. HvidstenAbstract:Background: Understanding how complex traits evolve through adaptive changes in gene regulation remains a major challenge in evolutionary biology. Over the last ~50 million years, Earth has experienced climate cooling and ancestrally tropical plants have adapted to expanding temperate environments. The grass subfamily Pooideae dominates the grass flora of the temperate regions, but conserved cold-response genes that might have played a role in the cold adaptation to temperate climate remain unidentified. Results: To establish if molecular responses to cold are conserved throughout the Pooideae phylogeny, we assembled the transcriptomes of five species spanning early to later diverging lineages, and compared short- and long-term cold response in orthologous genes based on gene expression data. We confirmed that most genes previously identified as cold responsive in barley also responded to cold in our barley experiment. Interestingly, comparing cold response across the lineages using 8633 high confidence ortholog groups revealed that nearly half of all cold responsive genes were species specific and more closely related species did not share higher numbers of cold responsive genes than more distantly related species. Also, the previously identified cold-responsive barley genes displayed low conservation of cold response across species. Nonetheless, more genes than expected by chance shared cold response, both based on previously studied genes and based on the high confidence ortholog groups. Noticeable, all five species shared short-term cold response in nine general stress genes as well as the ability to down-regulate the photosynthetic machinery during cold temperatures. Conclusions: We observed widespread lineage specific cold response in genes with conserved sequence across the Pooideae phylogeny. This is consistent with phylogenetic dating and historic temperature data which suggest that selection pressure resulting from dramatic global cooling must have acted on already diverged lineages. To what degree lineage specific evolution acted primarily through gain or loss of cold response remains unclear, however, phylogeny-wide conservation of certain genes and processes indicated that the last common ancestor may have possessed some cold response.
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Comparative transcriptomics reveals lineage specific evolution of cold response in Pooideae
2017Co-Authors: Lars Groenvold, Siri Fjellheim, Marian Schubert, Simen Rød Sandve, Torgeir R. HvidstenAbstract:Background: Understanding how complex traits evolve through adaptive changes in gene regulation remains a major challenge in evolutionary biology. Over the last ~50 million years, Earth has experienced climate cooling and ancestrally tropical plants have adapted to expanding temperate environments. The grass subfamily Pooideae dominates the grass flora of the temperate regions, but the role of cold-response gene regulation in the transitioning from tropical to temperate climate remains unexplored. Results: To establish if molecular responses to cold are conserved throughout the phylogeny, we assembled the transcriptomes of five Pooideae species spanning early to later diverging lineages, and compared short- and long-term cold responsive genes using 8633 high confidence ortholog groups with resolved gene tree topologies. We found that a majority of cold responsive genes were specific to one or two lineages, an observation that we deem incompatible with a cold adapted Pooideae ancestor. However, all five species shared short-term cold response in a small set of general stress genes as well as the ability to down-regulate the photosynthetic machinery during cold temperatures. Conclusions: Our observations indicate that the different Pooideae lineages have assembled cold response programs in parallel by taking advantage of a common potential for cold adaptation.
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evidence for adaptive evolution of low temperature stress response genes in a Pooideae grass ancestor
New Phytologist, 2013Co-Authors: Magnus Dehli Vigeland, Siri Fjellheim, Odd Arne Rognli, Manuel Spannagl, Torben Asp, Cristiana Paina, Heidi Rudi, Simen Rød SandveAbstract:Summary Adaptation to temperate environments is common in the grass subfamily Pooideae, suggesting an ancestral origin of cold climate adaptation. Here, we investigated substitution rates of genes involved in low-temperature-induced (LTI) stress responses to test the hypothesis that adaptive molecular evolution of LTI pathway genes was important for Pooideae evolution. Substitution rates and signatures of positive selection were analyzed using 4330 gene trees including three warm climate-adapted species (maize (Zea mays), sorghum (Sorghum bicolor), and rice (Oryza sativa)) and five temperate Pooideae species (Brachypodium distachyon, wheat (Triticum aestivum), barley (Hordeum vulgare), Lolium perenne and Festuca pratensis). Nonsynonymous substitution rate differences between Pooideae and warm habitat-adapted species were elevated in LTI trees compared with all trees. Furthermore, signatures of positive selection were significantly stronger in LTI trees after the rice and Pooideae split but before the Brachypodium divergence (P < 0.05). Genome-wide heterogeneity in substitution rates was also observed, reflecting divergent genome evolution processes within these grasses. Our results provide evidence for a link between adaptation to cold habitats and adaptive evolution of LTI stress responses in early Pooideae evolution and shed light on a poorly understood chapter in the evolutionary history of some of the world's most important temperate crops.
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Increased above-ground resource allocation is a likely precursor for independent evolutionary origins of annuality in the Pooideae grass subfamily.
The New phytologist, 2020Co-Authors: Camilla Lorange Lindberg, Marian Schubert, Thomas Marcussen, Ben Trevaskis, Jill C. Preston, Hans Martin Hanslin, Siri FjellheimAbstract:Semelparous annual plants flower a single time during their 1-yr life cycle, investing much of their energy into rapid reproduction. By contrast, iteroparous perennial plants flower multiple times over several years, and partition their resources between reproduction and persistence. To which extent evolutionary transitions between life-cycle strategies are internally constrained at the developmental, genetic and phylogenetic level is unknown. Here we study the evolution of life-cycle strategies in the grass subfamily Pooideae and test if transitions between them are facilitated by evolutionary precursors. We integrate ecological, life-cycle strategy and growth data in a phylogenetic framework. We investigate if growth traits are candidates for a precursor. Species in certain Pooideae clades are predisposed to evolve annuality from perenniality, potentially due to the shared inheritance of specific evolutionary precursors. Seasonal dry climates, which have been linked to annuality, were only able to select for transitions to annuality when the precursor was present. Allocation of more resources to above-ground rather than below-ground growth is a candidate for the precursor. Our findings support the hypothesis that only certain lineages can respond quickly to changing external conditions by switching their life-cycle strategy, likely due to the presence of evolutionary precursors.
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the grass subfamily Pooideae cretaceous palaeocene origin and climate driven cenozoic diversification
Global Ecology and Biogeography, 2019Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:AIM: Frost is among the most dramatic stresses a plant can experience, and complex physiological adaptations are needed to endure long periods of sub‐zero temperatures. Owing to the need to evolve these complex adaptations, transitioning from tropical to temperate climates is regarded as difficult. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates cool temperate, continental and Arctic regions. We produce a dated phylogeny and investigate the role of climate cooling in diversification. LOCATION: Global, temperate regions. TIME PERIOD: Cretaceous–Cenozoic. MAJOR TAXA: Pooideae. METHODS: Using newly available fossils and methods, we dated a comprehensive Pooideae phylogeny and tested for the impact of palaeoclimates on diversification rates. Using ancestral state reconstruction, we investigated whether Pooideae ancestors experienced frost and winter. To locate the ancestral distribution area of Pooideae, we performed biogeographical analyses. RESULTS: We estimated a Late Cretaceous/early Palaeocene origin of the Pooideae (61–77 Ma), with all major clades already having diversified at the Eocene–Oligocene climate cooling (34 Ma). Climate cooling was a probable driving force of Pooideae diversification. Pooideae probably evolved in a temperate niche experiencing frost, but not long winters. MAIN CONCLUSION: Pooideae probably originated in a temperate niche and experienced cold temperatures and frost long before expansion of temperate biomes after the Eocene–Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that certain responses to low‐temperature stress are shared in extant Pooideae grasses. Throughout the Cenozoic, falling temperatures and expansion of temperate biomes were associated with an increase in diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most probably evolved independently in daughter lineages. Our findings provide insight into how adaptations to historical changes in chill and frost exposure influence the distribution of plant diversity today.
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The grass subfamily Pooideae: Cretaceous–Palaeocene origin and climate‐driven Cenozoic diversification
Global Ecology and Biogeography, 2019Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:AIM: Frost is among the most dramatic stresses a plant can experience, and complex physiological adaptations are needed to endure long periods of sub‐zero temperatures. Owing to the need to evolve these complex adaptations, transitioning from tropical to temperate climates is regarded as difficult. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates cool temperate, continental and Arctic regions. We produce a dated phylogeny and investigate the role of climate cooling in diversification. LOCATION: Global, temperate regions. TIME PERIOD: Cretaceous–Cenozoic. MAJOR TAXA: Pooideae. METHODS: Using newly available fossils and methods, we dated a comprehensive Pooideae phylogeny and tested for the impact of palaeoclimates on diversification rates. Using ancestral state reconstruction, we investigated whether Pooideae ancestors experienced frost and winter. To locate the ancestral distribution area of Pooideae, we performed biogeographical analyses. RESULTS: We estimated a Late Cretaceous/early Palaeocene origin of the Pooideae (61–77 Ma), with all major clades already having diversified at the Eocene–Oligocene climate cooling (34 Ma). Climate cooling was a probable driving force of Pooideae diversification. Pooideae probably evolved in a temperate niche experiencing frost, but not long winters. MAIN CONCLUSION: Pooideae probably originated in a temperate niche and experienced cold temperatures and frost long before expansion of temperate biomes after the Eocene–Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that certain responses to low‐temperature stress are shared in extant Pooideae grasses. Throughout the Cenozoic, falling temperatures and expansion of temperate biomes were associated with an increase in diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most probably evolved independently in daughter lineages. Our findings provide insight into how adaptations to historical changes in chill and frost exposure influence the distribution of plant diversity today.
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The grass subfamily Pooideae: late Cretaceous origin and climate-driven Cenozoic diversification
2018Co-Authors: Marian Schubert, Thomas Marcussen, Andrea S. Meseguer, Siri FjellheimAbstract:Aim: Frost is among the most dramatic stresses a plant can experience and complex physiological adaptations are needed to endure long periods of sub-zero temperatures. Due to the need for evolving these complex adaptations, transitioning from tropical to temperate climates is regarded difficult and only half of the world9s seed plant families have temperate representatives. Here, we study the transition from tropical to temperate climates in the grass subfamily Pooideae, which dominates the northern temperate grass floras. Specifically, we investigate the role of climate cooling in diversification. Location: Global, temperate regions Time period: Late Cretaceous-Cenozoic Major taxa: The grass subfamily Pooideae Methods: We date a comprehensive Pooideae phylogeny and test for the impact of paleoclimates on diversification rates. Using ancestral state reconstruction, we investigate if Pooideae ancestors experienced frost and winter. To locate the area of origin of Pooideae we perform biogeographical analyses. Results: We estimated a late Cretaceous origin of the Pooideae (66 million years ago (Mya)), and all major clades had already diversified at the Eocene-Oligocene transition climate cooling (34 Mya). Climate cooling was a probable driving force of Pooideae diversification. Pooideae likely evolved in mountainous regions of southwestern Eurasia in a temperate niche experiencing frost, but not long winters. Main conclusion: Pooideae originated in a temperate niche and experienced cold temperatures and frost long before the expansion of temperate biomes after the Eocene-Oligocene transition. This suggests that the Pooideae ancestor had adaptations to temperate climate and that extant Pooideae grasses share responses to low temperature stress in Pooideae. Throughout the Cenozoic falling temperatures triggered diversification. However, complex mechanisms for enduring strongly seasonal climate with long, cold winters most likely evolved independently in lower taxonomic lineages. Our findings provide insight into how adaptations to historic changes in chill and frost exposure influence distribution of plant diversity today.
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Evidence for an Early Origin of Vernalization Responsiveness in Temperate Pooideae Grasses
Plant physiology, 2016Co-Authors: Meghan Mckeown, Siri Fjellheim, Marian Schubert, Thomas Marcussen, Jill C. PrestonAbstract:The ability of plants to match their reproductive output with favorable environmental conditions has major consequences both for lifetime fitness and geographic patterns of diversity. In temperate ecosystems, some plant species have evolved the ability to use winter nonfreezing cold (vernalization) as a cue to ready them for spring flowering. However, it is unknown how important the evolution of vernalization responsiveness has been for the colonization and subsequent diversification of taxa within the northern and southern temperate zones. Grasses of subfamily Pooideae, including several important crops, such as wheat (Triticum aestivum), barley (Hordeum vulgare), and oats (Avena sativa), predominate in the northern temperate zone, and it is hypothesized that their radiation was facilitated by the early evolution of vernalization responsiveness. Predictions of this early origin hypothesis are that a response to vernalization is widespread within the subfamily and that the genetic basis of this trait is conserved. To test these predictions, we determined and reconstructed vernalization responsiveness across Pooideae and compared expression of wheat vernalization gene orthologs VERNALIZATION1 (VRN1) and VRN3 in phylogenetically representative taxa under cold and control conditions. Our results demonstrate that vernalization responsive Pooideae species are widespread, suggesting that this trait evolved early in the lineage and that at least part of the vernalization gene network is conserved throughout the subfamily. These results are consistent with the hypothesis that the evolution of vernalization responsiveness was important for the initial transition of Pooideae out of the tropics and into the temperate zone.
