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Hiroyuki Mizuta - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the Sporophyte-Preferential Gene Promoter from the Red Alga Porphyra yezoensis Using Transient Gene Expression
Marine Biotechnology, 2013Co-Authors: Hiroyuki Mizuta, Naotsune SagaAbstract:The life cycle of plants entails an alternation of generations, the diploid Sporophyte and haploid gametophyte stages. There is little information about the characteristics of gene expression during each phase of marine macroalgae. Promoter analysis is a useful method for understanding transcriptional regulation; however, there is no report of promoter analyses in marine macroalgae. In this study, with the aim of elucidating the differences in the transcriptional regulatory mechanisms between the gametophyte and Sporophyte stages in the marine red alga Porphyra yezoensis , we isolated the promoter from the Sporophyte preferentially expressed gene PyKPA1 , which encodes a sodium pump, and analyzed its promoter using a transient gene expression system with a synthetic β-glucuronidase (PyGUS) reporter. The deletion of −1432 to −768 relative to the transcription start site resulted in decreased GUS activity in Sporophytes. In contrast, deletion from −767 to −527 increased GUS activity in gametophytes. Gain-of-function analyses showed that the −1432 to −760 region enhanced the GUS activity of a heterologous promoter in Sporophytes, whereas the −767 to −510 region repressed it in gametophytes. Further mutation and gain-of-function analyses of the −767 to −510 region revealed that a 20-bp GC-rich sequence (−633 to −614) is responsible for the gametophyte-specific repressed expression. These results showed that the Sporophyte-specific positive regulatory region and gametophyte-specific negative regulatory sequence play a crucial role in the preferential expression of PyKPA1 in P. yezoensis Sporophytes.
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Regulation of Sorus Formation by Auxin in Laminariales Sporophyte
Journal of Applied Phycology, 2006Co-Authors: Tomoki Kai, Hajime Yasui, Kazumi Nimura, Hiroyuki MizutaAbstract:Young Sporophytes of Laminaria japonica Areshoug were cultured in six indole-acetic acid (IAA) concentrations (0, 10−8, 10−7, 10−6, 10−5, 10−4 M) to examine the effect of auxin on growth. The effects of auxin on sorus formation were also examined by using discs taken from the adult Sporophyte. The auxin contents and IAA oxidase activities in the thallus and sorus parts of the Sporophyte were determined with the blade and sporophyll of other Laminariales plants, Undaria pinnatifida (Harvey) Suringar and Alaria crassifolia Kjellman. The young Sporophytes of L. japonica showed highest elongation rate in 10−5 M IAA. In contrast, the sorus formation on the discs cultured in 10−5 M IAA was markedly delayed in comparison with other concentrations, indicating that sorus formation was suppressed by IAA. Free and conjugated auxin contents were lower in the reproductive parts than in the vegetative parts. In three Laminariales Sporophytes, IAA oxidase activity was about 3–9 times higher in the reproductive parts than in the vegetative parts. Taken together these results suggest that the growth and reproduction of Laminariales Sporophytes are regulated by internal auxin levels. Elucidating the regulation mechanism is likely to provide information that is important for the management of plant production and the assessment of the physiological status of plants in the field.
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Inducible effects of abscisic acid on Sporophyte discs from Laminaria japonica Areschoug (Laminariales, Phaeophyceae)
Journal of Applied Phycology, 2002Co-Authors: Kazumi Nimura, Hiroyuki MizutaAbstract:The effects of exogenous abscisic acid (ABA;10^−7–10^−5 M), a knownplantgrowth regulator, on reproduction and growth were investigated by culturingdiscs from Sporophytes of Laminaria japonica Areschoug.ABAplays a role in triggering sorus formation, and it was found that sorusformation of discs was fastest in 10^−5 M ABA. Theapplication of 10^−5 M ABA to culturing discs alsosuppressed the expansion of surface area. ABA contents in sorus and vegetativeparts of the Sporophyte were determined by bioassay. The mean ABA content insorus parts obtained from Sporophytes was 0.222 ± 0.053μg equivalent-ABA g wet weight^−1, which wasabout five times higher than the content found in vegetative parts (0.048± 0.009 μg equivalent-ABA g wetweight^−1). Taken together these results suggest that sorusdevelopment requires an elevated level of ABA and is associated with decreasingvegetative growth and that the ABA level of the Sporophyte may play a crucialrole in reproduction.
Akira F Peters - One of the best experts on this subject based on the ideXlab platform.
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convergent recruitment of tale homeodomain life cycle regulators to direct Sporophyte development in land plants and brown algae
eLife, 2019Co-Authors: Alok Arun, Akira F Peters, Delphine Scornet, Susana M. Coelho, Simon Bourdareau, Laurent Peres, Martina Strittmatter, Agnieszka P Lipinska, Haiqin Yao, Olivier GodfroyAbstract:Brown algae and land plants are two groups of multicellular organisms that have been evolving independently for over a billion years. Their last common ancestor is thought to have existed as a single cell; then, complex multicellular organisms would have appeared separately in each lineage. Comparing brown algae and land plants therefore helps us understand the rules that guide how multicellular organisms evolve from single-celled ancestors. During their life cycles, both brown algae and land plants alternate between two multicellular forms: the gametophyte and the Sporophyte. The gametophyte develops sexually active reproductive cells, which, when they merge, create the Sporophyte. In turn, spores produced by the Sporophyte give rise to the gametophyte. Specific developmental programs are deployed at precise points in the life cycle to make either a Sporophyte or a gametophyte. Two proteins known as TALE HD transcription factors help to control the life cycle of single-celled algae related to land plants. Similar proteins are also required for the Sporophyte to develop at the right time in land plants known as mosses. This suggests that, when multicellular organisms emerged in this lineage, life cycle TALE HD transcription factors were recruited to orchestrate the development of the Sporophyte. However, it was not clear whether TALE HD transcription factors play equivalent roles in other groups, such as brown algae. To address this question, Arun, Coelho et al. examined two mutants of the brown alga Ectocarpus, which produce gametophytes when the non-mutated alga would have made Sporophytes. Genetic analyses revealed that these mutated brown algae carried changes in two genes that encode TALE HD transcription factors, indicating that these proteins also regulate the formation of Sporophytes in brown algae. Taken together, the results suggest that TALE HD transcription factors were originally tasked with controlling life cycles, and then have been independently harnessed in both land plants and brown algae to govern the formation of Sporophytes. This means that, regardless of lineage, the same fundamental forces may be shaping the evolutionary paths that lead to multicellular organisms. Proteins similar to TALE HD transcription factors also regulate life cycles in other groups such as fungi and social amoebae, which indicates that their role is very ancient. It now remains to be explored whether such proteins control life cycles and developmental programs in other multicellular organisms, such as animals.
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Examining the bank of microscopic stages in kelps using culturing and barcoding
European Journal of Phycology, 2014Co-Authors: Marine Robuchon, Akira F Peters, Lucia Couceiro, Christophe Destombe, Myriam ValeroAbstract:This paper describes a method to study the diversity of young kelp Sporophytes that are recruited from the bank of microscopic stages. Small samples of rocky substratum (0.5 cm2) were collected from the low intertidal zone, which was dominated by the kelp Laminaria digitata. Samples were cultivated in the laboratory under conditions permitting gametogenesis. Sporophyte recruits in the cultures were isolated and identified at the species level using the barcoding mitochondrial marker rpl31–rns. Sixty per cent of the collected samples had at least one to a maximum of 30 kelp recruits, belonging to five different species (L. digitata, L. hyperborea, L. ochroleuca, Saccharina latissima and Sacchorhiza polyschides). As the examination of freshly collected rocky samples under a stereo microscope did not reveal any kelp Sporophytes, the recruitment in these samples after culture probably occurred from the bank of microscopic forms present on the substratum. Despite the dominance of L. digitata in the field, the young Sporophytes obtained after culturing were mainly S. polyschides. This study illustrates the suitability of culturing in combination with molecular identification of young Sporophytes to address several key aspects of kelp ecology related to the existence of a bank of microscopic stages in the field.
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Life-cycle-generation-specific developmental processes are modified in the immediate upright mutant of the brown alga Ectocarpus siliculosus
Development (Cambridge England), 2008Co-Authors: Akira F Peters, Delphine Scornet, Morgane Ratin, Bénédicte Charrier, Annabelle Monnier, Yves Merrien, Erwan Corre, Susana M. Coelho, J. Mark CockAbstract:Development of the Sporophyte and gametophyte generations of the brown alga E. siliculosus involves two different patterns of early development, which begin with either a symmetric or an asymmetric division of the initial cell, respectively. A mutant, immediate upright (imm), was isolated that exhibited several characteristics typical of the gametophyte during the early development of the Sporophyte generation. Genetic analyses showed that imm is a recessive, single-locus Mendelian factor and analysis of gene expression in this mutant indicated that the regulation of a number of life-cycle-regulated genes is specifically modified in imm mutant Sporophytes. Thus, IMM appears to be a regulatory locus that controls part of the Sporophyte-specific developmental programme, the mutant exhibiting partial homeotic conversion of the Sporophyte into the gametophyte, a phenomenon that has not been described previously.
Delphine Scornet - One of the best experts on this subject based on the ideXlab platform.
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Production and Bioassay of a Diffusible Factor That Induces Gametophyte-to-Sporophyte Developmental Reprogramming in the Brown Alga Ectocarpus
Bio-protocol, 2020Co-Authors: Haiqin Yao, Delphine Scornet, Yacine Badis, Akira Peters, Murielle Jam, Cécile Hervé, Philippe Potin, Susana Coelho, J. CockAbstract:The brown alga Ectocarpus has a haploid-diploid life cycle that involves alternation between two multicellular generations, the Sporophyte and the gametophyte. Life cycle generation is not determined by ploidy but by a genetic system that includes two different three amino acid loop extension homeodomain transcription factors called OUROBOROS and SAMSARA. In addition, Sporophytes have been shown to secrete a diffusible factor into the medium that can induce gametophyte initial cells to switch from the gametophyte to the Sporophyte developmental program. The protocol presented here describes how to produce Sporophyte-conditioned medium containing the diffusible Sporophyte-inducing factor and how to assay for activity of the factor using a meio-spore-based bioassay. The protocol, which describes how several steps of these procedures can be optimised, will represent a useful tool for future work aimed at characterising the diffusible factor and investigating its mode of action.
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convergent recruitment of tale homeodomain life cycle regulators to direct Sporophyte development in land plants and brown algae
eLife, 2019Co-Authors: Alok Arun, Akira F Peters, Delphine Scornet, Susana M. Coelho, Simon Bourdareau, Laurent Peres, Martina Strittmatter, Agnieszka P Lipinska, Haiqin Yao, Olivier GodfroyAbstract:Brown algae and land plants are two groups of multicellular organisms that have been evolving independently for over a billion years. Their last common ancestor is thought to have existed as a single cell; then, complex multicellular organisms would have appeared separately in each lineage. Comparing brown algae and land plants therefore helps us understand the rules that guide how multicellular organisms evolve from single-celled ancestors. During their life cycles, both brown algae and land plants alternate between two multicellular forms: the gametophyte and the Sporophyte. The gametophyte develops sexually active reproductive cells, which, when they merge, create the Sporophyte. In turn, spores produced by the Sporophyte give rise to the gametophyte. Specific developmental programs are deployed at precise points in the life cycle to make either a Sporophyte or a gametophyte. Two proteins known as TALE HD transcription factors help to control the life cycle of single-celled algae related to land plants. Similar proteins are also required for the Sporophyte to develop at the right time in land plants known as mosses. This suggests that, when multicellular organisms emerged in this lineage, life cycle TALE HD transcription factors were recruited to orchestrate the development of the Sporophyte. However, it was not clear whether TALE HD transcription factors play equivalent roles in other groups, such as brown algae. To address this question, Arun, Coelho et al. examined two mutants of the brown alga Ectocarpus, which produce gametophytes when the non-mutated alga would have made Sporophytes. Genetic analyses revealed that these mutated brown algae carried changes in two genes that encode TALE HD transcription factors, indicating that these proteins also regulate the formation of Sporophytes in brown algae. Taken together, the results suggest that TALE HD transcription factors were originally tasked with controlling life cycles, and then have been independently harnessed in both land plants and brown algae to govern the formation of Sporophytes. This means that, regardless of lineage, the same fundamental forces may be shaping the evolutionary paths that lead to multicellular organisms. Proteins similar to TALE HD transcription factors also regulate life cycles in other groups such as fungi and social amoebae, which indicates that their role is very ancient. It now remains to be explored whether such proteins control life cycles and developmental programs in other multicellular organisms, such as animals.
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Life-cycle-generation-specific developmental processes are modified in the immediate upright mutant of the brown alga Ectocarpus siliculosus
Development (Cambridge England), 2008Co-Authors: Akira F Peters, Delphine Scornet, Morgane Ratin, Bénédicte Charrier, Annabelle Monnier, Yves Merrien, Erwan Corre, Susana M. Coelho, J. Mark CockAbstract:Development of the Sporophyte and gametophyte generations of the brown alga E. siliculosus involves two different patterns of early development, which begin with either a symmetric or an asymmetric division of the initial cell, respectively. A mutant, immediate upright (imm), was isolated that exhibited several characteristics typical of the gametophyte during the early development of the Sporophyte generation. Genetic analyses showed that imm is a recessive, single-locus Mendelian factor and analysis of gene expression in this mutant indicated that the regulation of a number of life-cycle-regulated genes is specifically modified in imm mutant Sporophytes. Thus, IMM appears to be a regulatory locus that controls part of the Sporophyte-specific developmental programme, the mutant exhibiting partial homeotic conversion of the Sporophyte into the gametophyte, a phenomenon that has not been described previously.
Lloyd R. Stark - One of the best experts on this subject based on the ideXlab platform.
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Developing Sporophytes transition from an inducible to a constitutive ecological strategy of desiccation tolerance in the moss Aloina ambigua: effects of desiccation on fitness
Annals of Botany, 2015Co-Authors: Lloyd R. Stark, John C. BrindaAbstract:Background and Aims Two ecological strategies of desiccation tolerance exist in plants, constitutive and inducible. Because of difficulties in culturing Sporophytes, very little is known about desiccation tolerance in this generation and how desiccation affects sexual fitness. Methods Cultured Sporophytes and vegetative shoots from a single genotype of the moss Aloina ambigua raised in the laboratory were tested for their strategy of desiccation tolerance by desiccating the shoot–Sporophyte complex and vegetative shoots at different intensities, and comparing outcomes with those of undried shoot–Sporophyte complexes and vegetative shoots. By using a dehardened clonal line, the effects of field, age and genetic variance among plants were removed. Key Results The gametophyte and embryonic Sporophyte were found to employ a predominantly inducible strategy of desiccation tolerance, while the post-embryonic Sporophyte was found to employ a moderately constitutive strategy of desiccation tolerance. Further, desiccation reduced Sporophyte fitness, as measured by Sporophyte mass, seta length and capsule size. However, the effects of desiccation on Sporophyte fitness were reduced if the stress occurred during embryonic development as opposed to postembryonic desiccation. Conclusions The effects of desiccation on dehardened Sporophytes of a bryophyte are shown for the first time. The transition from one desiccation tolerance strategy to the other in a single structure or generation is shown for only the second time in plants and for the first time in bryophytes. Finding degrees of inducible strategies of desiccation tolerance in different life phases prompts the formulation of a continuum hypothesis of ecological desiccation tolerance in mosses, where desiccation tolerance is not an either/or phenomenon, but varies in degree along a gradient of ecological inducibility.
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an experimental demonstration of the cost of sex and a potential resource limitation on reproduction in the moss pterygoneurum pottiaceae
American Journal of Botany, 2009Co-Authors: Lloyd R. Stark, John C. Brinda, Nicholas D McletchieAbstract:The cost of sexual reproduction is incurred when the current reproductive episode contributes to a a decline in future plant performance. To test the hypotheses that a trade-off exists between current sexual reproduction and subsequent clonal regeneration and that resources limit reproduction and regeneration, plants of the widespread moss Pterygoneurum ovatum were subjected to induced sporophytic abortion, upper leaf removal, and nutrient amendment treatments. Sexually reproducing plants were slower or less likely to produce regenerative structures (protonemata or shoots) and produced fewer regenerative tissue areas or structures. The ability and the timeline to reproduce sexually and regenerate clonally were unaffected by an inorganic nutrient amendment. However, when leaves subtending the Sporophyte were removed, the Sporophytes were less likely to mature, tended to take a longer time to mature, and were smaller compared to Sporophytes from shoots with a full complement of upper leaves. Our fi ndings indicate that plants investing in sexual reproduction suffer a cost of decreased clonal regeneration and indicate that Sporophyte maturation is resource-limited, with upper leaves contributing to the nutrition of the Sporophyte. This study represents only the second explicit experimental demonstration of a trade-off between sexual and asexual reproduction in bryophytes.
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Sporophyte and Gametophyte Generations Differ in their Thermotolerance Response in the Moss Microbryum
Annals of Botany, 2006Co-Authors: D. Nicholas Mcletchie, Lloyd R. StarkAbstract:Background and Aims Actively growing post-embryonic Sporophytes of desert mosses are restricted to the cooler, wetter months. However, most desert mosses have perennial gametophytes. It is hypothesized that these life history patterns are due in part to a reduced thermotolerance for Sporophytes relative to gametophytes. Methods Gametophytes with attached embryonic Sporophytes of Microbryum starckeanum were exposed whilst desiccated to thermal episodes of 35 C (1hr), 55 C (1hr), 75 C (1hr) and 75 C (3hr), then moistened and allowed to recover for 35d in a growth chamber. Key Results All of the gametophytes survived the thermal exposures and produced protonemata, with the majority also producing shoot buds. Symptoms of gametophytic stress (leaf burning and discoloration of entire shoots) were present inlower frequencies inthe 55 C exposure. Sporophyte resumption of growth and maturation tomeiosis were significantly negatively affected by thermal treatment. Not a single Sporophyte exposed to the two higher thermal treatments (75 C for 1hand 75 C for 3h) survived tomeiosis, and those Sporophytes exposed to 75 C that survived to the post-embryonic phenophase took significantly longer to reach this phase. Furthermore, among the thermal treatments where some capsules reached maturity (35 C and 55 C), maternal shoots that produced a meiotic capsule took longer to regenerate through protonemata than maternal shoots aborting their Sporophyte, suggestive of a resource trade-off between generations. Conclusions Either (1) the inherent Sporophyte thermotolerance is quite low even in this desert moss, and/or (2) a gametophytic thermal stress response controls Sporophyte viability.
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Skipped reproductive cycles and extensive Sporophyte abortion in the desert moss Tortula inermis correspond to unusual rainfall patterns
Canadian Journal of Botany, 2002Co-Authors: Lloyd R. StarkAbstract:A phenological assessment of Tortula inermis (Brid.) Mont. populations in the Mojave Desert, Nevada, U.S.A., over a period of 4 years revealed that the Sporophyte cohort initiated in early 1995 remained dormant until early 1998, by which time approximately 66% of the Sporophytes had aborted. The viable Sporophytes of this cohort were significantly shorter in length and had significantly less biomass than the previous cohort of Sporophytes. In the intervening years 1996 and 1997, the sexual reproductive cycle was skipped altogether. The absence of Sporophyte initiation in these two years was attributed to reduced winterspring rainfall. The majority of abortive Sporophytes aborted in the late embryonic and seta elongation phenophases. The 1997 and 1998 summers were characterized by unusually heavy rains. Following the heavy summer rain events of 1997, Sporophyte abortion in the 1995 cohort increased from 9 to 43%, and abortive Sporophytes in this cohort further increased to 66% following the summer rains o...
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widespread Sporophyte abortion following summer rains in mojave desert populations ofgrimmia orbicularis
The Bryologist, 2001Co-Authors: Lloyd R. StarkAbstract:Abstract Widespread abortion of Sporophytes in the desert moss Grimmia orbicularis occurred following unusually heavy summer rainstorms in the Mojave Desert of southern Nevada. Approximately 50% of the Sporophyte cohort aborted, the majority in the seta elongation phenophase. Just prior to the abortions, an August rain event equivalent to one-half of the normal annual precipitation occurred over a period of less than six hours. Abortive Sporophytes were significantly shorter and had significantly less biomass than viable mature Sporophytes from the same cohort. A phenological and length analysis of the Sporophyte cohort indicates that the Sporophyte abortions occurred over a very brief period of time. It is postulated that the stresses brought on by desiccation/rehydration cycles during the summer heat in the desert, in conjunction with the presence of an abnormally advanced phenophase (early seta elongation), may have resulted in an inability to either repair the cellular damage or resulted in insufficie...
Hironori Mizuta - One of the best experts on this subject based on the ideXlab platform.
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Control of elicitor-induced oxidative burst by abscisic acid associated with growth of Saccharina japonica (Phaeophyta, Laminariales) Sporophytes
Journal of Applied Phycology, 2017Co-Authors: Kazuki Shimizu, Toshiki Uji, Hajime Yasui, Hironori MizutaAbstract:In this study, the oligoguluronate elicitor-induced oxidative burst (OB) was monitored continuously in young and mature Saccharina japonica Sporophytes based on luminol chemiluminescence using a photon counter. The iodoperoxidase (IPO) activity, abscisic acid (ABA), and polyphenol contents were also compared in the different growth stages. The elicitor-induced OB occurred within 1 min and reached its maximum in 15–20 min after treatment in all growth stages. The active elicitor-induced OB was stronger in the young Sporophytes than the older Sporophytes. The IPO activity in the different growth stages also exhibited a similar pattern to the elicitor-induced OB. These results suggest that the elicitor-induced OB and the subsequent high haloperoxidase activity comprise a major defence mechanism in young Sporophytes. By contrast, ABA accumulated with the growth of the Sporophytes. Interestingly, ABA treatment suppressed the elicitor-induced OB during growth and enhanced the elicitor-independent IPO activity even in the young Sporophytes. In addition, the polyphenol content was higher in the older Sporophytes than the younger Sporophytes. These observations show that dramatic changes occur in the characteristic defences against biotic stresses as the Sporophyte grows, as well as suggesting that ABA is closely linked with these changes. Moreover, the IPO activity recovered slightly in the sorus, which is the reproductive tissue, thereby suggesting that a higher ABA content increases the defence activity and the success of reproduction.
