Dataset Information

BdVRN1 Expression Confers Flowering Competency and Is Negatively Correlated with Freezing Tolerance in Brachypodium distachyon.

ABSTRACT: Vernalization is an essential process by which many temperate plant species acquire competence for flowering. Brachypodium distachyon is a model plant for temperate grasses including many cool-season forage and turfgrasses and cereals. Grasses with spring growth habit do not require vernalization for flowering and are typically less winter hardy. Yet the connection between vernalization and freezing tolerance remain unclear. The diverse requirement of vernalization for flowering makes it an ideal choice for studying the relationship between vernalization and freezing tolerance. Here, we isolated and analyzed the spatial and temporal expression patterns of two vernalization related homologous genes, BdVRN1 and BdVRN3 in Bd21, a non-vernalization-requiring accession, and Bd29-1, an accession shown to be vernalization-requiring. We showed that expression of BdVRN1 and BdVRN3 is independent of vernalization in Bd21, but is vernalization dependent in Bd29-1. Moreover, vernalization-induced expression of BdVRN1 appears to precede that of BdVRN3 in Bd29-1. Bd21 RNAi knockdown mutants for BdVRN1 conferred vernalization requirement for flowering, and reduced the expression of BdVRN3. Both Bd29-1 and the BdVRN1 RNAi mutants of Bd21 exhibited reduced freezing tolerance upon vernalization treatment. Cold-responsive genes BdCBF2, BdCBF3, BdCBF5, BdCBF6, and BdDREB2A were all constitutively expressed at a high level in the BdVRN1 RNAi mutants of Bd21. Taken together, our results suggest that expression of BdVRN1 promotes flowering by upregulating BdVRN3, and gaining the competency for flowering reduces freezing tolerance in Brachypodium.

SUBMITTER: Feng Y

PROVIDER: S-EPMC5479923 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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BdVRN1 Expression Confers Flowering Competency and Is Negatively Correlated with Freezing Tolerance in Brachypodium distachyon.

Feng Ying Y Yin Yanhai Y Fei Shuizhang S

Frontiers in plant science 20170622

Vernalization is an essential process by which many temperate plant species acquire competence for flowering. Brachypodium distachyon is a model plant for temperate grasses including many cool-season forage and turfgrasses and cereals. Grasses with spring growth habit do not require vernalization for flowering and are typically less winter hardy. Yet the connection between vernalization and freezing tolerance remain unclear. The diverse requirement of vernalization for flowering makes it ...[more]

PMID: 28690631

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Project description:Background and aimsCold is a major constraint for cereal cultivation under temperate climates. Winter-hardy plants interpret seasonal changes and can acquire the ability to resist sub-zero temperatures. This cold acclimation process is associated with physiological, biochemical and molecular alterations in cereals. Brachypodium distachyon is considered a powerful model system to study the response of temperate cereals to adverse environmental conditions. To date, little is known about the cold acclimation and freezing tolerance capacities of Brachypodium. The main objective of this study was to evaluate the cold hardiness of seven diploid Brachypodium accessions.MethodsAn integrated approach, involving monitoring of phenological indicators along with expression profiling of the major vernalization regulator VRN1 orthologue, was followed. In parallel, soluble sugars and proline contents were determined along with expression profiles of two COR genes in plants exposed to low temperatures. Finally, whole-plant freezing tests were performed to evaluate the freezing tolerance capacity of Brachypodium.Key resultsCold treatment accelerated the transition from the vegetative to the reproductive phase in all diploid Brachypodium accessions tested. In addition, low temperature exposure triggered the gradual accumulation of BradiVRN1 transcripts in all accessions tested. These accessions exhibited a clear cold acclimation response by progressively accumulating proline, sugars and COR gene transcripts. However, whole-plant freezing tests revealed that these seven diploid accessions only have a limited capacity to develop freezing tolerance when compared with winter varieties of temperate cereals such as wheat and barley. Furthermore, little difference in terms of survival was observed among the accessions tested despite their previous classification as either spring or winter genotypes.ConclusionsThis study is the first to characterize the freezing tolerance capacities of B. distachyon and provides strong evidence that some diploid accessions such as Bd21 have a facultative growth habit.

Project description:Brachypodium distachyon (Brachypodium) is a model for the temperate grasses which include important cereals such as barley, wheat and oats. Comparison of the Brachypodium genome (accession Bd21) with those of the model dicot Arabidopsis thaliana and the tropical cereal rice (Oryza sativa) provides an opportunity to compare and contrast genetic pathways controlling important traits. We analysed the homologies of genes controlling the induction of flowering using pathways curated in Arabidopsis Reactome as a starting point. Pathways include those detecting and responding to the environmental cues of day length (photoperiod) and extended periods of low temperature (vernalization). Variation in these responses has been selected during cereal domestication, providing an interesting comparison with the wild genome of Brachypodium. Brachypodium Bd21 has well conserved homologues of circadian clock, photoperiod pathway and autonomous pathway genes defined in Arabidopsis and homologues of vernalization pathway genes defined in cereals with the exception of VRN2 which was absent. Bd21 also lacked a member of the CO family (CO3). In both cases flanking genes were conserved showing that these genes are deleted in at least this accession. Segmental duplication explains the presence of two CO-like genes in temperate cereals, of which one (Hd1) is retained in rice, and explains many differences in gene family structure between grasses and Arabidopsis. The conserved fine structure of duplications shows that they largely evolved to their present structure before the divergence of the rice and Brachypodium. Of four flowering-time genes found in rice but absent in Arabidopsis, two were found in Bd21 (Id1, OsMADS51) and two were absent (Ghd7, Ehd1). Overall, results suggest that an ancient core photoperiod pathway promoting flowering via the induction of FT has been modified by the recruitment of additional lineage specific pathways that promote or repress FT expression.

Dataset Information

BdVRN1 Expression Confers Flowering Competency and Is Negatively Correlated with Freezing Tolerance in Brachypodium distachyon.

Publications

<i>BdVRN1</i> Expression Confers Flowering Competency and Is Negatively Correlated with Freezing Tolerance in <i>Brachypodium distachyon</i>.

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