Vernalization

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Richard M Amasino - One of the best experts on this subject based on the ideXlab platform.

  • establishment of a Vernalization requirement in brachypodium distachyon requires repressor of Vernalization1
    Proceedings of the National Academy of Sciences of the United States of America, 2017
    Co-Authors: Daniel P Woods, Thomas S Ream, Frederic Bouche, Nicholas Thrower, Curtis G Wilkerson, Richard M Amasino
    Abstract:

    Abstract A requirement for Vernalization, the process by which prolonged cold exposure provides competence to flower, is an important adaptation to temperate climates that ensures flowering does not occur before the onset of winter. In temperate grasses, Vernalization results in the up-regulation of Vernalization1 (VRN1) to establish competence to flower; however, little is known about the mechanism underlying repression of VRN1 in the fall season, which is necessary to establish a Vernalization requirement. Here, we report that a plant-specific gene containing a bromo-adjacent homology and transcriptional elongation factor S-II domain, which we named REPRESSOR OF Vernalization1 (RVR1), represses VRN1 before Vernalization in Brachypodium distachyon. That RVR1 is upstream of VRN1 is supported by the observations that VRN1 is precociously elevated in an rvr1 mutant, resulting in rapid flowering without cold exposure, and the rapid-flowering rvr1 phenotype is dependent on VRN1. The precocious VRN1 expression in rvr1 is associated with reduced levels of the repressive chromatin modification H3K27me3 at VRN1, which is similar to the reduced VRN1 H3K27me3 in vernalized plants. Furthermore, the transcriptome of vernalized wild-type plants overlaps with that of nonvernalized rvr1 plants, indicating loss of rvr1 is similar to the vernalized state at a molecular level. However, loss of rvr1 results in more differentially expressed genes than does Vernalization, indicating that RVR1 may be involved in processes other than Vernalization despite a lack of any obvious pleiotropy in the rvr1 mutant. This study provides an example of a role for this class of plant-specific genes.

  • a methyltransferase required for proper timing of the Vernalization response in arabidopsis
    Proceedings of the National Academy of Sciences of the United States of America, 2015
    Co-Authors: Wei Zhao, Wenhui Shen, Richard M Amasino
    Abstract:

    Prolonged exposure to winter cold enables flowering in many plant species through a process called Vernalization. In Arabidopsis, Vernalization results from the epigenetic silencing of the floral repressor FLOWERING LOCUS C (FLC) via a Polycomb Repressive Complex 2 (PRC2)-mediated increase in the density of the epigenetic silencing mark H3K27me3 at FLC chromatin. During cold exposure, a gene encoding a unique, cold-specific PRC2 component, Vernalization INSENSITIVE 3 (VIN3), which is necessary for PRC2-mediated silencing of FLC, is induced. Here we show that SET DOMAIN GROUP 7 (SDG7) is required for proper timing of VIN3 induction and of the Vernalization process. Loss of SDG7 results in a Vernalization-hypersensitive phenotype, as well as more rapid cold-mediated up-regulation of VIN3. In the absence of cold, loss of SDG7 results in elevated levels of long noncoding RNAs, which are thought to participate in epigenetic repression of FLC. Furthermore, loss of SDG7 results in increased H3K27me3 deposition on FLC chromatin in the absence of cold exposure and enhanced H3K27me3 spreading during cold treatment. Thus, SDG7 is a negative regulator of Vernalization, and loss of SDG7 creates a partially vernalized state without cold exposure.

  • interaction of photoperiod and Vernalization determines flowering time of brachypodium distachyon
    Plant Physiology, 2014
    Co-Authors: Thomas S Ream, Daniel P Woods, Christopher J Schwartz, Claudia P Sanabria, Jill A Mahoy, Eric M Walters, Heidi F Kaeppler, Richard M Amasino
    Abstract:

    Timing of flowering is key to the reproductive success of many plants. In temperate climates, flowering is often coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization is an example of temperature influencing the timing of flowering and is defined as the process by which a prolonged exposure to the cold of winter results in competence to flower during the following spring. In cereals, three genes (Vernalization1 [VRN1], VRN2, and FLOWERING LOCUS T [FT]) have been identified that influence the Vernalization requirement and are thought to form a regulatory loop to control the timing of flowering. Here, we characterize natural variation in the Vernalization and photoperiod responses in Brachypodium distachyon, a small temperate grass related to wheat (Triticum aestivum) and barley (Hordeum vulgare). Brachypodium spp. accessions display a wide range of flowering responses to different photoperiods and lengths of Vernalization. In addition, we characterize the expression patterns of the closest homologs of VRN1, VRN2 (VRN2-like [BdVRN2L]), and FT before, during, and after cold exposure as well as in different photoperiods. FT messenger RNA levels generally correlate with flowering time among accessions grown in different photoperiods, and FT is more highly expressed in vernalized plants after cold. VRN1 is induced by cold in leaves and remains high following Vernalization. Plants overexpressing VRN1 or FT flower rapidly in the absence of Vernalization, and plants overexpressing VRN1 exhibit lower BdVRN2L levels. Interestingly, BdVRN2L is induced during cold, which is a difference in the behavior of BdVRN2L compared with wheat VRN2 during cold.

  • the molecular basis of Vernalization in different plant groups
    Cold Spring Harbor Symposia on Quantitative Biology, 2012
    Co-Authors: Thomas S Ream, Daniel P Woods, Richard M Amasino
    Abstract:

    : Timing of flowering is key to the reproductive success of many plants. In temperate climates, flowering is often coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization, the process by which a prolonged exposure to the cold of winter results in competence to flower during the following spring, is an example of the influence of temperature on the timing of flowering. In different groups of plants, there are distinct genes involved in Vernalization, indicating that Vernalization systems evolved independently in different plant groups. The convergent evolution of Vernalization systems is not surprising given that angiosperm families had begun to diverge in warmer paleoclimates in which a Vernalization response was not advantageous. Here, we review what is known of the Vernalization response in three different plant groups: crucifers (Arabidopsis), Amaranthaceae (sugar beet), and Pooideae (wheat, barley, and Brachypodium distachyon). We also discuss the advantages of using Brachypodium as a model system to study flowering and Vernalization in the Pooids. Finally, we discuss the evolution and function of the Ghd7/VRN2 gene family in grasses.

  • Vernalization winter and the timing of flowering in plants
    Annual Review of Cell and Developmental Biology, 2009
    Co-Authors: Mark R Doyle, Sibum Sung, Richard M Amasino
    Abstract:

    Plants have evolved many systems to sense their environment and to modify their growth and development accordingly. One example is Vernalization, the process by which flowering is promoted as plants sense exposure to the cold temperatures of winter. A requirement for Vernalization is an adaptive trait that helps prevent flowering before winter and permits flowering in the favorable conditions of spring. In Arabidopsis and cereals, Vernalization results in the suppression of genes that repress flowering. We describe recent progress in understanding the molecular basis of this suppression. In Arabidopsis, Vernalization involves the recruitment of chromatin-modifying complexes to a clade of flowering repressors that are silenced epigenetically via histone modifications. We also discuss the similarities and differences in Vernalization between Arabidopsis and cereals.

Jorge Dubcovsky - One of the best experts on this subject based on the ideXlab platform.

  • fine mapping and epistatic interactions of the Vernalization gene vrn d4 in hexaploid wheat
    Molecular Genetics and Genomics, 2014
    Co-Authors: Nestor Kippes, Andrew Chen, Jorge Dubcovsky, Leonardo Sebastian Vanzetti, Adam J Lukaszewski, Hidetaka Nishida, Kenji Kato, Jan Dvorak
    Abstract:

    Wheat Vernalization requirement is mainly controlled by the VRN1, VRN2, VRN3, and VRN4 genes. The first three have been cloned and have homoeologs in all three genomes. VRN4 has been found only in the D genome (VRN-D4) and has not been cloned. We constructed a high-density genetic map of the VRN-D4 region and mapped VRN-D4 within a 0.09 cM interval in the centromeric region of chromosome 5D. Using telocentric 5D chromosomes generated from the VRN-D4 donor Triple Dirk F, we determined that VRN-D4 is located on the short arm. The VRN-D4 candidate region is colinear with a 2.24 Mb region on Brachypodium distachyon chromosome 4, which includes 127 predicted genes. Ten of these genes have predicted roles in development but we detected no functional polymorphisms associated to VRN-D4. Two recombination events separated VRN-D4 from TaVIL-D1, the wheat homolog of Arabidopsis Vernalization gene VIL1, confirming that this gene is not a candidate for VRN-D4. We detected significant interactions between VRN-D4 and other four genes controlling Vernalization requirement (Vrn-A1, Vrn-B1, Vrn-D1, and Vrn-B3), which confirmed that VRN-D4 is part of the Vernalization pathway and that it is either upstream or is part of the regulatory feedback loop involving VRN1, VRN2 and VRN3 genes. The precise mapping of VRN-D4 and the characterization of its interactions with other Vernalization genes provide valuable information for the utilization of VRN-D4 in wheat improvement and for our current efforts to clone this Vernalization gene.

  • wheat tilling mutants show that the Vernalization gene vrn1 down regulates the flowering repressor vrn2 in leaves but is not essential for flowering
    PLOS Genetics, 2012
    Co-Authors: Andrew Chen, Jorge Dubcovsky
    Abstract:

    Most of the natural variation in wheat Vernalization response is determined by allelic differences in the MADS-box transcription factor Vernalization1 (VRN1). Extended exposures to low temperatures during the winter (Vernalization) induce VRN1 expression and promote the transition of the apical meristem to the reproductive phase. In contrast to its Arabidopsis homolog (APETALA1), which is mainly expressed in the apical meristem, VRN1 is also expressed at high levels in the leaves, but its function in this tissue is not well understood. Using tetraploid wheat lines with truncation mutations in the two homoeologous copies of VRN1 (henceforth vrn1-null mutants), we demonstrate that a central role of VRN1 in the leaves is to maintain low transcript levels of the VRN2 flowering repressor after Vernalization. Transcript levels of VRN2 were gradually down-regulated during Vernalization in both mutant and wild-type genotypes, but were up-regulated after Vernalization only in the vrn1-null mutants. The up-regulation of VRN2 delayed flowering by repressing the transcription of FT, a flowering-integrator gene that encodes a mobile protein that is transported from the leaves to the apical meristem to induce flowering. The role of VRN2 in the delayed flowering of the vrn1-null mutant was confirmed using double vrn1-vrn2-null mutants, which flowered two months earlier than the vrn1-null mutants. Both mutants produced normal flowers and seeds demonstrating that VRN1 is not essential for wheat flowering, which contradicts current flowering models. This result does not diminish the importance of VRN1 in the seasonal regulation of wheat flowering. The up-regulation of VRN1 during winter is required to maintain low transcript levels of VRN2, accelerate the induction of FT in the leaves, and regulate a timely flowering in the spring. Our results also demonstrate the existence of redundant wheat flowering genes that may provide new targets for engineering wheat varieties better adapted to changing environments.

  • allelic variation at the Vernalization genes vrn a1 vrn b1 vrn d1 and vrn b3 in chinese wheat cultivars and their association with growth habit
    Crop Science, 2008
    Co-Authors: Jorge Dubcovsky, X K Zhang, Yonggui Xiao, Yan Zhang, Zhonghu He
    Abstract:

    Information on the distribution of Vernalization genes and their association with growth habit is crucial to understanding the adaptability of wheat (Triticum aestivum L.) cultivars to different environments. In this study, 278 Chinese wheat cultivars were characterized with molecular markers for the Vernalization genes Vrn-A1, -B1, -D1, and -B3. Heading time was evaluated in a greenhouse under long days without vernalizaton. The dominant Vrn-D1 allele showed the highest frequency in the Chinese wheat cultivars (37.8%), followed by the dominant Vrn-A1, -B1, and -B3 alleles. Ninety-two winter cultivars carried recessive alleles of all four Vernalization loci, whereas 172 spring genotypes contained at least one dominant Vrn allele. All cultivars released in the North China Plain Winter Wheat Zone were winter type. Winter (53.0%), spring (36.1%), and early-heading (10.9%) cultivars were grown in the Yellow and Huai River Valley Winter Zone. Most of the spring genotypes from this zone carried only the dominant Vrn-D1 allele, which was also predominant (64.1%) in the Middle and Lower Yangtze Valley Winter Zone and Southwestern Winter Wheat Zone. In three spring-sown wheat zones, all cultivars were early-heading spring types that frequently possessed the strongest dominant Vrn-A1a allele and combinations with other dominant Vrn gene(s). The Vrn-D1 allele is associated with the latest heading time, Vrn-A1 the earliest, and Vrn-B1 intermediate values. The information is important for breeding programs in countries interested in using Chinese wheats.

  • the wheat vrn2 gene is a flowering repressor down regulated by Vernalization
    Science, 2004
    Co-Authors: Artem Loukoianov, Ann E Blechl, G Tranquilli, Wusirika Ramakrishna, Phillip Sanmiguel, Jeffrey L Bennetzen, Viviana Echenique, Jorge Dubcovsky
    Abstract:

    Plants with a winter growth habit flower earlier when exposed for several weeks to cold temperatures, a process called Vernalization. We report here the positional cloning of the wheat Vernalization gene VRN2, a dominant repressor of flowering that is down-regulated by Vernalization. Loss of function of VRN2, whether by natural mutations or deletions, resulted in spring lines, which do not require Vernalization to flower. Reduction of the RNA level of VRN2 by RNA interference accelerated the flowering time of transgenic winter-wheat plants by more than a month.

  • comparative rflp mapping of triticum monococcum genes controlling Vernalization requirement
    Theoretical and Applied Genetics, 1998
    Co-Authors: Jorge Dubcovsky, Diego Lijavetzky, L Appendino, G Tranquilli
    Abstract:

    The adaptability of Triticum aestivum to a large range of environments is partially due to genetic differences in sensitivity to Vernalization. The most potent gene reducing the Vernalization requirement in hexaploid wheat is Vrn-A1. An orthologous Vernalization gene, designated Vrn-A m 1, was mapped in the diploid wheat Triticum monococcum between RFLP markers Xwg908 and Xabg702 on the long arm of chromosome 5AmL. The orthology of VrnA m 1 with Vrn-A1 (5A wheat, originally Vrn1), Vrn-D1 (5D wheat, originally Vrn3), Vrn-R1 (5R rye, originally Sp1) and Vrn-H1 (5H barley, originally Sh2) was shown by mapping RFLP markers linked to these Vernalization genes on the T. monococcum linkage map. A second Vernalization gene, designated Vrn-A m 2, was found in the distal region of chromosome 5AmL within a segment translocated from homoeologous group 4. This gene is completely linked to RFLP marker Xbcd402 and located between the same RFLP markers (Xβ-Amy-1 and Xmwg616) as the Vrn-H2 (originally Sh) locus in Hordeum vulgare.

Ildiko Karsai - One of the best experts on this subject based on the ideXlab platform.

  • fine tuning of the flowering time control in winter barley the importance of hvos2 and hvvrn2 in non inductive conditions
    BMC Plant Biology, 2019
    Co-Authors: Arantxa Monteagudo, Ernesto Igartua, Bruno Contrerasmoreira, Pilar M Gracia, Javier Ramos, Ildiko Karsai, Ana M Casas
    Abstract:

    Background In winter barley plants, Vernalization and photoperiod cues have to be integrated to promote flowering. Plant development and expression of different flowering promoter (HvVRN1, HvCO2, PPD-H1, HvFT1, HvFT3) and repressor (HvVRN2, HvCO9 and HvOS2) genes were evaluated in two winter barley varieties under: (1) natural increasing photoperiod, without Vernalization, and (2) under short day conditions in three insufficient Vernalization treatments. These challenging conditions were chosen to capture non-optimal and natural responses, representative of those experienced in the Mediterranean area.

  • long day increase of hvvrn2 expression marks the deadline to fulfill the Vernalization requirement in winter barley
    bioRxiv, 2018
    Co-Authors: Arantxa Monteagudo, Ernesto Igartua, Ildiko Karsai, M P Gracia, Ana M Casas
    Abstract:

    Vernalization and photoperiod cues are integrated in winter barley plants to flower in the right conditions. We hypothesize that there is a timeframe to satisfy the Vernalization needs in order to flower in the optimum moment. Growth and expression of different flowering promoters ( HvVRN1 , HvCO2 , Ppd-H1 , HvFT1 , HvFT3 ) and repressors ( HvVRN2 , HvCO9 and HvOS2 ) were evaluated in two winter barley varieties under: (1) natural increasing photoperiod, without Vernalization, and (2) under short day conditions in three insufficient Vernalization treatments. Here, we provide evidence of the existence of a day-length threshold, around 12 h 30 min in our latitudes (Zaragoza, Spain, 41°43′N), marked by the rise of HvVRN2 expression, which defines the moment in which cold requirement must be satisfied to acquire competency to flower. Before that, expression of HvCO2 was induced and might be promoting HvFT1 in both inductive and non-inductive conditions. HvFT3 , to be effectively expressed, must receive induction of cold or plant development, through downregulation of HvVRN2 and HvOS2 . We emphasize the contribution of HvOS2 , together with HvVRN2 , in the delay of flowering in Vernalization-responsive cultivars. Understanding this complex mechanism of flowering might be useful for breeders to define varieties, particularly in a climate change scenario.

  • expression analysis of Vernalization and day length response genes in barley hordeum vulgare l indicates that vrnh2 is a repressor of ppdh2 hvft3 under long days
    Journal of Experimental Botany, 2011
    Co-Authors: Cristina M Casao, Ernesto Igartua, Pilar M Gracia, Ildiko Karsai, J M Lasa, Ana M Casas
    Abstract:

    The response to Vernalization and the expression of genes associated with responses to Vernalization (VRNH1, VRNH2, and VRNH3) and photoperiod (PPDH1 and PPDH2) were analysed in four barley (Hordeum vulgare L.) lines: ‘Alexis’ (spring), ‘Plaisant’ (winter), SBCC058, and SBCC106 (Spanish inbred lines), grown under conditions of Vernalization and short days (VSD) or no Vernalization and long days (NVLD). The four genotypes differ in VRNH1. Their growth habits and responses to Vernalization correlated with the level of expression of VRNH1 and the length of intron 1. ‘Alexis’ and ‘Plaisant’ behaved as expected. SBCC058 and SBCC106 showed an intermediate growth habit and flowered relatively late in the absence of Vernalization. VRNH1 expression was induced by cold for all genotypes. Under VSD, VRNH1 expression was detected in the SBCC genotypes later than in ‘Alexis’ but earlier than in ‘Plaisant’. VRNH2 was repressed under short days while VRNH1 expression increased in parallel. VRNH3 was detected only in ‘Alexis’ under NVLD, whereas it was not expressed in plants with the active allele of VRNH2 (SBCC058 and ‘Plaisant’). Under VSD, PPDH2 was expressed in ‘Alexis’, SBCC058, and SBCC106, but it was only expressed weakly in ‘Alexis’ under NVLD. Further analysis of PPDH2 expression in two barley doubled haploid populations revealed that, under long days, HvFT3 and VRNH2 expression levels were related inversely. The timing of VRNH2 expression under a long photoperiod suggests that this gene might be involved in repression of PPDH2 and, indirectly, in the regulation of flowering time through an interaction with the day-length pathway.

  • validation of the vrn h2 vrn h1 epistatic model in barley reveals that intron length variation in vrn h1 may account for a continuum of Vernalization sensitivity
    Molecular Genetics and Genomics, 2007
    Co-Authors: P Szucs, Ildiko Karsai, Tony H H Chen, Jeffrey S Skinner, Alfonso Cuestamarcos, Kale G Haggard, Ann Corey, Patrick M Hayes
    Abstract:

    The epistatic interaction of alleles at the VRN-H1 and VRN-H2 loci determines Vernalization sensitivity in barley. To validate the current molecular model for the two-locus epistasis, we crossed homozygous Vernalization-insensitive plants harboring a predicted “winter type” allele at either VRN-H1 (Dicktoo) or VRN-H2 (Oregon Wolfe Barley Dominant), or at both VRN-H (Calicuchima-sib) loci and measured the flowering time of unvernalized F2 progeny under long-day photoperiod. We assessed whether the spring growth habit of Calicuchima-sib is an exception to the two-locus epistatic model or contains novel “spring” alleles at VRN-H1 (HvBM5A) and/or VRN-H2 (ZCCT-H) by determining allele sequence variants at these loci and their effects relative to growth habit. We found that (a) progeny with predicted “winter type” alleles at both VRN-H1 and VRN-H2 alleles exhibited an extremely delayed flowering (i.e. Vernalization-sensitive) phenotype in two out of the three F2 populations, (b) sequence flanking the Vernalization critical region of HvBM5A intron 1 likely influences degree of Vernalization sensitivity, (c) a winter habit is retained when ZCCT-Ha has been deleted, and (d) the ZCCT-H genes have higher levels of allelic polymorphism than other winterhardiness regulatory genes. Our results validate the model explaining the epistatic interaction of VRN-H2 and VRN-H1 under long-day conditions, demonstrate recovery of Vernalization-sensitive progeny from crosses of Vernalization-insensitive genotypes, show that intron length variation in VRN-H1 may account for a continuum of Vernalization sensitivity, and provide molecular markers that are accurate predictors of “winter vs spring type” alleles at the VRN-H loci.

  • validation of the two gene epistatic model for Vernalization response in a winter spring barley cross
    Euphytica, 2006
    Co-Authors: K Koti, Ildiko Karsai, K Meszaros, P Szűcs, Cs Horvath, G Kiss, Zoltan Bedő, P M Hayes
    Abstract:

    A two gene epistatic model in which a dominant “winter growth habit” allele at Vrn-H2 encodes a repressor with a corresponding binding site in a recessive vrn-H1 allele explains the Vernalization response phenotypes in an array of barley germplasm. In order to validate the model genetically, we developed an F 2 population (and F 2-derived F 3 families) from the cross of Hardy (winter) × Jubilant (spring). Using gene-specific primers, we determined the Vrn-H1 and Vrn-H2 allele architecture of each F 2 plant and we measured the growth habit phenotype of each F 2 plant via phenotyping of its F 3 progeny under controlled environment conditions. We used a set of treatments involving plus/minus Vernalization under long photoperiod and Vernalization under short photoperiod. Alleles at the two loci showed expected patterns of segregation and independent assortment. Under long day conditions, the two Vrn genes were the primary determinants of heading date, regardless of the Vernalization treatment. Under short photoperiod, the effects of these loci were not significant. There was incomplete dominance at Vrn-H1: heterozygotes were significantly later to head than Vrn-H1Vrn-H1 genotypes. Vrn-H2 genotypes were also significantly later to head, even when plants were vernalized. These results validate the two-gene epistatic model for Vernalization response under long-day conditions. The results under short photoperiod, and the variance in flowering with Vernalization, confirm that while the two Vrn genes are the primary determinants of Vernalization response, they are part of a larger interactome that determines the timing of the vegetative to reproductive transition.

Ben Trevaskis - One of the best experts on this subject based on the ideXlab platform.

  • transcriptome analysis of the Vernalization response in barley hordeum vulgare seedlings
    PLOS ONE, 2011
    Co-Authors: Sandra N Oliver, Shahryar Sasani, Aaron Greenup, Sally A Walford, Anthony A Millar, Ben Trevaskis
    Abstract:

    Temperate cereals, such as wheat (Triticum spp.) and barley (Hordeum vulgare), respond to prolonged cold by becoming more tolerant of freezing (cold acclimation) and by becoming competent to flower (Vernalization). These responses occur concomitantly during winter, but Vernalization continues to influence development during spring. Previous studies identified Vernalization1 (VRN1) as a master regulator of the Vernalization response in cereals. The extent to which other genes contribute to this process is unclear. In this study the Barley1 Affymetrix chip was used to assay gene expression in barley seedlings during short or prolonged cold treatment. Gene expression was also assayed in the leaves of plants after prolonged cold treatment, in order to identify genes that show lasting responses to prolonged cold, which might contribute to Vernalization-induced flowering. Many genes showed altered expression in response to short or prolonged cold treatment, but these responses differed markedly. A limited number of genes showed lasting responses to prolonged cold treatment. These include genes known to be regulated by Vernalization, such as VRN1 and ODDSOC2, and also contigs encoding a calcium binding protein, 23-KD jasmonate induced proteins, an RNase S-like protein, a PR17d secretory protein and a serine acetyltransferase. Some contigs that were up-regulated by short term cold also showed lasting changes in expression after prolonged cold treatment. These include COLD REGULATED 14B (COR14B) and the barley homologue of WHEAT COLD SPECIFIC 19 (WSC19), which were expressed at elevated levels after prolonged cold. Conversely, two C-REPEAT BINDING FACTOR (CBF) genes showed reduced expression after prolonged cold. Overall, these data show that a limited number of barley genes exhibit lasting changes in expression after prolonged cold treatment, highlighting the central role of VRN1 in the Vernalization response in cereals.

  • oddsoc2 is a mads box floral repressor that is down regulated by Vernalization in temperate cereals
    Plant Physiology, 2010
    Co-Authors: Aaron Greenup, Sandra N Oliver, Elizabeth S Dennis, Shahryar Sasani, Megan N Hemming, Mark J Talbot, Ben Trevaskis
    Abstract:

    In temperate cereals, such as wheat (Triticum aestivum) and barley (Hordeum vulgare), the transition to reproductive development can be accelerated by prolonged exposure to cold (Vernalization). We examined the role of the grass-specific MADS box gene ODDSOC2 (OS2) in the Vernalization response in cereals. The barley OS2 gene (HvOS2) is expressed in leaves and shoot apices but is repressed by Vernalization. Vernalization represses OS2 independently of Vernalization1 (VRN1) in a VRN1 deletion mutant of einkorn wheat (Triticum monococcum), but VRN1 is required to maintain down-regulation of OS2 in vernalized plants. Furthermore, barleys that carry active alleles of the VRN1 gene (HvVRN1) have reduced expression of HvOS2, suggesting that HvVRN1 down-regulates HvOS2 during development. Overexpression of HvOS2 delayed flowering and reduced spike, stem, and leaf length in transgenic barley plants. Plants overexpressing HvOS2 showed reduced expression of barley homologs of the Arabidopsis (Arabidopsis thaliana) gene FLOWERING PROMOTING FACTOR1 (FPF1) and increased expression of RNase-S-like genes. FPF1 promotes floral development and enhances cell elongation, so down-regulation of FPF1-like genes might explain the phenotypes of HvOS2 overexpression lines. We present an extended model of the genetic pathways controlling Vernalization-induced flowering in cereals, which describes the regulatory relationships between VRN1, OS2, and FPF1-like genes. Overall, these findings highlight differences and similarities between the Vernalization responses of temperate cereals and the model plant Arabidopsis.

  • the central role of the Vernalization1 gene in the Vernalization response of cereals
    Functional Plant Biology, 2010
    Co-Authors: Ben Trevaskis
    Abstract:

    Many varieties of wheat (Triticum spp.) and barley (Hordeum vulgare L.) require prolonged exposure to cold during winter in order to flower (Vernalization). In these cereals, Vernalization-induced flowering is controlled by the Vernalization1 (VRN1) gene. VRN1 is a promoter of flowering that is activated by low temperatures. VRN1 transcript levels increase gradually during Vernalization, with longer cold treatments inducing higher expression levels. Elevated VRN1 expression is maintained in the shoot apex and leaves after Vernalization, and the level of VRN1 expression in these organs determines how rapidly vernalized plants flower. Some alleles of VRN1 are expressed without Vernalization due to deletions or insertions within the promoter or first intron of the VRN1 gene. Varieties of wheat and barley with these alleles flower without Vernalization and are grown where Vernalization does not occur. The first intron of the VRN1 locus has histone modifications typically associated with the maintenance of an inactive chromatin state, suggesting this region is targeted by epigenetic mechanisms that contribute to repression of VRN1 before winter. Other mechanisms are likely to act elsewhere in the VRN1 gene to mediate low-temperature induction. This review examines how understanding the mechanisms that regulate VRN1 provides insights into the biology of Vernalization-induced flowering in cereals and how this will contribute to future cereal breeding strategies.

  • Regions associated with repression of the barley (Hordeum vulgare) Vernalization1 gene are not required for cold induction
    Molecular Genetics and Genomics, 2009
    Co-Authors: Megan N Hemming, Elizabeth S Dennis, Sarah Fieg, W. James Peacock, Ben Trevaskis
    Abstract:

    Activity of the Vernalization1 ( VRN1 ) gene is required for flowering in temperate cereals such as wheat and barley. In varieties that require prolonged exposure to cold to flower (Vernalization), VRN1 is expressed at low levels and is induced by Vernalization to trigger flowering. In other varieties, deletions or insertions in the first intron of the VRN1 gene are associated with increased VRN1 expression in the absence of cold treatment, reducing or eliminating the requirement for Vernalization. To characterize natural variation in VRN1 , the first intron of the barley ( Hordeum vulgare ) VRN1 gene (HvVRN1) was assayed for deletions or insertions in a collection of 1,000 barleys from diverse geographical regions. Ten alleles of HvVRN1 containing deletions or insertions in the first intron were identified, including three alleles that have not been described previously. Different HvVRN1 alleles were associated with differing levels of HvVRN1 expression in non-vernalized plants and with different flowering behaviour. Using overlapping deletions, we delineated regions in the HvVRN1 first intron that are associated with low levels of HvVRN1 expression in non-vernalized plants. Deletion of these intronic regions does not prevent induction of HvVRN1 by cold or the maintenance of increased HvVRN1 expression following cold treatment. We suggest that regions within the first intron of HvVRN1 are required to maintain low levels of HvVRN1 expression prior to winter but act independently of the regulatory mechanisms that mediate induction of HvVRN1 by cold during winter.

  • the molecular biology of seasonal flowering responses in arabidopsis and the cereals
    Annals of Botany, 2009
    Co-Authors: Aaron Greenup, Elizabeth S Dennis, W J Peacock, Ben Trevaskis
    Abstract:

    †Background In arabidopsis (Arabidopsis thaliana), FLOWERING LOCUS T (FT) and FLOWERING LOCUS C (FLC) play key roles in regulating seasonal flowering-responses to synchronize flowering with optimal conditions. FT is a promoter of flowering activated by long days and by warm conditions. FLC represses FT to delay flowering until plants experience winter. †Scope The identification of genes controlling flowering in cereals allows comparison of the molecular pathways controlling seasonal flowering-responses in cereals with those of arabidopsis. The role of FT has been conserved between arabidopsis and cereals; FT-like genes trigger flowering in response to short days in rice or long days in temperate cereals, such as wheat (Triticum aestivum) and barley (Hordeum vulgare). Many varieties of wheat and barley require Vernalization to flower but FLC-like genes have not been identified in cereals. Instead, Vernalization2 (VRN2) inhibits long-day induction of FT-like1 (FT1) prior to winter. Vernalization1 (VRN1) is activated by low-temperatures during winter to repress VRN2 and to allow the long-day response to occur in spring. In rice (Oryza sativa )a VRN2-like gene Ghd7, which influences grain number, plant height and heading date, represses the FT-like gene Heading date 3a (Hd3a) in long days, suggesting a broader role for VRN2-like genes in regulating day-length responses in cereals. Other genes, including Early heading date (Ehd1), Oryza sativa MADS51 (OsMADS51) and INDETERMINATE1 (OsID1) up-regulate Hd3a in short days. These genes might account for the different day-length response of rice compared with the temperate cereals. No genes homologous to VRN2, Ehd1, Ehd2 or OsMADS51 occur in arabidopsis. †Conclusions It seems that different genes regulate FT orthologues to elicit seasonal flowering-responses in arabidopsis and the cereals. This highlights the need for more detailed study into the molecular basis of seasonal flowering-responses in cereal crops or in closely related model plants such as Brachypodium distachyon.

Caroline Dean - One of the best experts on this subject based on the ideXlab platform.

  • seasonal shift in timing of Vernalization as an adaptation to extreme winter
    eLife, 2015
    Co-Authors: Susan Duncan, Svante Holm, Julia I Questa, Judith A Irwin, Alastair Grant, Caroline Dean
    Abstract:

    Plants are not able to move around and so they need to be able to adapt their growth and development to seasonal changes in their environment. For example, prolonged exposure to cold temperatures during winter can prime some plants to flower when temperatures increase in the spring—a process called Vernalization. In these plants, extended periods of cold temperatures lead to lower activity of a gene called FLC, which normally inhibits flowering. In the plant Arabidopsis thaliana, Vernalization requires several months of exposure to temperatures between 0–6°C. Recently, A. thaliana plants from southern Europe were found to vary in the temperature requirements for Vernalization, responding to temperatures higher than 6°C. This suggested that plants from northern Europe might vernalize preferentially at lower temperatures. Here, Duncan et al. compared Vernalization in a collection of A. thaliana plants (or ‘accessions’) sampled from different regions of Sweden and the UK. The experiments show that all the accessions needed temperatures above 0°C to vernalize and that Vernalization still worked relatively well at temperatures as high as 14°C. The optimal temperature range for Vernalization differed between the accessions, but plants from more northern areas did not necessarily vernalize at lower temperatures. For example, for one particular accession from northern Sweden, the temperature that is optimum for Vernalization was 8°C, a notably higher temperature than expected. Historical local climate records suggested that this accession would vernalize before the first snowfall of the winter in North Sweden. Duncan et al. confirmed this proposal with field experiments. Plants were grown in natural field sites in September and then moved into a greenhouse. The experiments show that the plants complete Vernalization by November, which strongly suggests that FLC is silenced during autumn rather than during winter, as previously thought. This changed temperature response is due, in part, to a small number of tiny genetic differences in regions of the FLC gene that do not code for protein. These findings have important implications for future studies of Vernalization and flowering time, and for understanding how plants will adapt to on going and future climate change. The next step is to understand what causes these changed temperature responses at a molecular level, which should enable selective breeding for flowering and harvest date in a range of crops.

  • Vernalization a cold induced epigenetic switch
    Journal of Cell Science, 2012
    Co-Authors: Jie Song, Andrew Angel, Martin Howard, Caroline Dean
    Abstract:

    Summary Growth and development are modulated by environmental signals in many organisms. These signals are often perceived at one stage and ‘remembered’ until later in development. An increasingly well-understood example of this process in plants is provided by Vernalization, which refers to the acquisition of the ability to flower after prolonged exposure to cold. In Arabidopsis thaliana, Vernalization involves downregulation and epigenetic silencing of the gene encoding the floral repressor FLOWERING LOCUS C (FLC). This epigenetic silencing is quantitative and increases with the duration of exposure to cold. Vernalization involves a Polycomb-based switching mechanism, with localized nucleation of silencing during periods of cold, and spreading of the silencing complex over the whole gene after the exposure to cold. A number of characteristics of Vernalization have recently been elaborated on through the use of mathematical modelling. This has revealed the importance of chromatin dynamics for the switching mechanism and has shown that the quantitative nature of the process is due to cell-autonomous switching of an increasing proportion of cells. The principles derived from Vernalization are likely to be widely relevant to epigenetic reprogramming in many organisms.

  • Vernalization – a cold-induced epigenetic switch
    Journal of Cell Science, 2012
    Co-Authors: Jie Song, Andrew Angel, Martin Howard, Caroline Dean
    Abstract:

    Summary Growth and development are modulated by environmental signals in many organisms. These signals are often perceived at one stage and ‘remembered’ until later in development. An increasingly well-understood example of this process in plants is provided by Vernalization, which refers to the acquisition of the ability to flower after prolonged exposure to cold. In Arabidopsis thaliana, Vernalization involves downregulation and epigenetic silencing of the gene encoding the floral repressor FLOWERING LOCUS C (FLC). This epigenetic silencing is quantitative and increases with the duration of exposure to cold. Vernalization involves a Polycomb-based switching mechanism, with localized nucleation of silencing during periods of cold, and spreading of the silencing complex over the whole gene after the exposure to cold. A number of characteristics of Vernalization have recently been elaborated on through the use of mathematical modelling. This has revealed the importance of chromatin dynamics for the switching mechanism and has shown that the quantitative nature of the process is due to cell-autonomous switching of an increasing proportion of cells. The principles derived from Vernalization are likely to be widely relevant to epigenetic reprogramming in many organisms.

  • major effect alleles at relatively few loci underlie distinct Vernalization and flowering variation in arabidopsis accessions
    PLOS ONE, 2011
    Co-Authors: Amy Strange, Chikako Shindo, Clare Lister, Magnus Nordborg, Judith A Irwin, Peijin Li, Jillian Anderson, Norman Warthmann, Caroline Dean
    Abstract:

    We have explored the genetic basis of variation in Vernalization requirement and response in Arabidopsis accessions, selected on the basis of their phenotypic distinctiveness. Phenotyping of F2 populations in different environments, plus fine mapping, indicated possible causative genes. Our data support the identification of FRI and FLC as candidates for the major-effect QTL underlying variation in Vernalization response, and identify a weak FLC allele, caused by a Mutator-like transposon, contributing to flowering time variation in two N. American accessions. They also reveal a number of additional QTL that contribute to flowering time variation after saturating Vernalization. One of these was the result of expression variation at the FT locus. Overall, our data suggest that distinct phenotypic variation in the Vernalization and flowering response of Arabidopsis accessions is accounted for by variation that has arisen independently at relatively few major-effect loci.

  • the phd finger protein vrn5 functions in the epigenetic silencing of arabidopsis flc
    Current Biology, 2007
    Co-Authors: Thomas Greb, Pedro Crevillen, Nuno Geraldo, Hailong An, Anthony R Gendall, Joshua S. Mylne, Caroline Dean
    Abstract:

    Summary Vernalization, the acceleration of flowering by the prolonged cold of winter, ensures that plants flower in favorable spring conditions. During Vernalization in Arabidopsis , cold temperatures repress FLOWERING LOCUS C ( FLC ) expression [1, 2] in a mechanism involving Vernalization INSENSITIVE 3 (VIN3) [3], and this repression is epigenetically maintained by a Polycomb-like chromatin regulation involving Vernalization 2 (VRN2), a Su(z)12 homolog, Vernalization 1 (VRN1), and LIKE-HETEROCHROMATIN PROTEIN 1 [4–8]. In order to further elaborate how cold repression triggers epigenetic silencing, we have targeted mutations that result in FLC misexpression both at the end of the prolonged cold and after subsequent development. This identified Vernalization 5 (VRN5), a PHD finger protein and homolog of VIN3. Our results suggest that during the prolonged cold, VRN5 and VIN3 form a heterodimer necessary for establishing the Vernalization-induced chromatin modifications, histone deacetylation, and H3 lysine 27 trimethylation required for the epigenetic silencing of FLC . Double mutant and FLC misexpression analyses reveal additional VRN5 functions, both FLC -dependent and -independent, and indicate a spatial complexity to FLC epigenetic silencing with VRN5 acting as a common component in multiple pathways.