Dissecting the Control of Flowering Time in Grasses Using Brachypodium distachyon

Woods, Daniel P.; Amasino, Richard M.

doi:10.1007/7397_2015_10

Cited by 17 publications

(18 citation statements)

References 63 publications

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“…Expression of VRN1 in the noncore pooid B. distachyon is consistent with it being conserved as floral promoter involved in vernalization ; for review on flowering in B. distachyon, see Woods and Amasino 2015). As in wheat and barley, B. distachyon VRN1 (BdVRN1) mRNA levels increase quantitatively during increasing durations of cold exposure and remain elevated post cold Woods et al, 2014).…”

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confidence: 67%

Evolution of VRN2/Ghd7-Like Genes in Vernalization-Mediated Repression of Grass Flowering

et al. 2016

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Flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization provides competence to flower after prolonged cold exposure, and a vernalization requirement prevents flowering from occurring prior to winter. In winter wheat (Triticum aestivum) and barley (Hordeum vulgare), three genes VRN1, VRN2, and FT form a regulatory loop that regulates the initiation of flowering. Prior to cold exposure, VRN2 represses FT. During cold, VRN1 expression increases, resulting in the repression of VRN2, which in turn allows activation of FT during long days to induce flowering. Here, we test whether the circuitry of this regulatory loop is conserved across Pooideae, consistent with their niche transition from the tropics to the temperate zone. Our phylogenetic analyses of VRN2-like genes reveal a duplication event occurred before the diversification of the grasses that gave rise to a CO9 and VRN2/Ghd7 clade and support orthology between wheat/barley VRN2 and rice (Oryza sativa) Ghd7. Our Brachypodium distachyon VRN1 and VRN2 knockdown and overexpression experiments demonstrate functional conservation of grass VRN1 and VRN2 in the promotion and repression of flowering, respectively. However, expression analyses in a range of pooids demonstrate that the cold repression of VRN2 is unique to core Pooideae such as wheat and barley. Furthermore, VRN1 knockdown in B. distachyon demonstrates that the VRN1-mediated suppression of VRN2 is not conserved. Thus, the VRN1-VRN2 feature of the regulatory loop appears to have evolved late in the diversification of temperate grasses.The initiation of flowering is a major developmental transition in the plant life cycle. When flowering initiates, shoot apical meristems shift from forming vegetative organs such as leaves to forming flowers. In many plant species, flowering occurs at a particular time of year in response to the sensing of seasonal cues such as changes in day length and temperature. In some plants adapted to temperate climates, exposure to the prolonged cold of winter (vernalization) results in the ability to flower in the next growing season (Chouard, 1960;Amasino, 2010). Although vernalization ultimately enables flowering, vernalization responsiveness is typically an adaptation to ensure that flowering does not occur prematurely in the fall season. This has obvious adaptive value; for example, many vernalization-responsive plants become established in the fall season (during which flowering would not lead to successful reproduction) and then rapidly flower in the spring when conditions for reproduction and seed maturation are optimal.The grass family (Poaceae) originated approximately 70 million years ago as part of the tropical forest understory. However, grasses have since diversified across the globe occupying a variety of ecological niches (Kellogg, 2001). Exemplifying this, the ;3,800 species of grass subfamily Pooideae, including the economically important cereals wheat (Triticum aestivum, Triticeae), barley (...

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confidence: 67%

Evolution of VRN2/Ghd7-Like Genes in Vernalization-Mediated Repression of Grass Flowering

et al. 2016

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“…The two major QTLs coincide with the location of the genes VRN1 and PHYC on chromosome 1 (QTL1) and VRN2 on chromosome 3 (QTL2). These genes have previously been shown to play important roles in flowering-time regulation in B. distachyon, and contribute to variation in flowering-time responses in wheat and barley (Woods et al, 2014b(Woods et al, , 2016Woods and Amasino 2015;Distelfeld et al, 2009). Thus, it appears that allelic variation in VRN1 and VRN2 likely contributes to flowering differences in an undomesticated pooid grass.…”

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confidence: 99%

Genetic Architecture of Flowering-Time Variation in Brachypodium distachyon

et al. 2016

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The transition to reproductive development is a crucial step in the plant life cycle, and the timing of this transition is an important factor in crop yields. Here, we report new insights into the genetic control of natural variation in flowering time in Brachypodium distachyon, a nondomesticated pooid grass closely related to cereals such as wheat (Triticum spp.) and barley (Hordeum vulgare L.). A recombinant inbred line population derived from a cross between the rapid-flowering accession Bd21 and the delayed-flowering accession Bd1-1 were grown in a variety of environmental conditions to enable exploration of the genetic architecture of flowering time. A genotyping-by-sequencing approach was used to develop SNP markers for genetic map construction, and quantitative trait loci (QTLs) that control differences in flowering time were identified. Many of the flowering-time QTLs are detected across a range of photoperiod and vernalization conditions, suggesting that the genetic control of flowering within this population is robust. The two major QTLs identified in undomesticated B. distachyon colocalize with VERNALIZATION1/PHYTOCHROME C and VERNALIZATION2, loci identified as flowering regulators in the domesticated crops wheat and barley. This suggests that variation in flowering time is controlled in part by a set of genes broadly conserved within pooid grasses.Proper timing of flowering is a major developmental decision in the life history of plants, and the genetic manipulation of flowering time has played a crucial role in the domestication and spread of cereal crops such as wheat (Triticum spp.), barley (Hordeum vulgare L.), rice (Oryza sativa), and maize (Zea mays; Greenup et al., 2009;Hung et al., 2012). Moreover, the modulation of flowering time has been important in the diversification of temperate (pooid) grasses into higher latitudes with colder winters (Woods et al., 2016;Fjellheim et al., 2014). An important environmental cue that often affects flowering is day (d) length (photoperiod; Song et al., 2015). Many plants adapted to temperate regions flower in response to increasing day lengths (long-d plants), in contrast to many plants from the tropics that flower as day length decreases (short-d plants). In addition, some plants adapted to temperate climates have taken on a biennial/winter annual life history strategy in which plants become established in the fall, then overwinter and flower rapidly in the spring as day lengths increase (Amasino 2010). Essential to this strategy is the prevention of flowering before winter because cold temperatures could damage delicate floral structures, preventing reproduction. Thus, plants have evolved ways to repress flowering in the fall and alleviate this repression by sensing the passing of winter to establish competence to flower. This process, by which the block to flowering is alleviated by exposure to prolonged time in cold temperatures, is known as vernalization (Chouard 1960).Many varieties of wheat, barley, oats (Avena sativa), and rye (Secale cereale) requ...

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“…Mur (Aberystwyth University), and F 1 plants were confirmed with CAPS markers ( S2 Table ). To increase F 2 seed yield, F 1 plants were grown in a prolonged vegetative state to increase biomass before vernalization and flowering [ 62 ]. F 2 lines were grown from a single cross for both Luc1 x Jer1 and Foz1 x Luc1.…”

Section: Methodsmentioning

confidence: 99%

The genetic architecture of colonization resistance in Brachypodium distachyon to non-adapted stripe rust (Puccinia striiformis) isolates

et al. 2018

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Multilayered defense responses ensure that plants are hosts to only a few adapted pathogens in the environment. The host range of a plant pathogen depends on its ability to fully overcome plant defense barriers, with failure at any single step sufficient to prevent life cycle completion of the pathogen. Puccinia striiformis, the causal agent of stripe rust (=yellow rust), is an agronomically important obligate biotrophic fungal pathogen of wheat and barley. It is generally unable to complete its life cycle on the non-adapted wild grass species Brachypodium distachyon, but natural variation exists for the degree of hyphal colonization by Puccinia striiformis. Using three B. distachyon mapping populations, we identified genetic loci conferring colonization resistance to wheat-adapted and barley-adapted isolates of P. striiformis. We observed a genetic architecture composed of two major effect QTLs (Yrr1 and Yrr3) restricting the colonization of P. striiformis. Isolate specificity was observed for Yrr1, whereas Yrr3 was effective against all tested P. striiformis isolates. Plant immune receptors of the nucleotide binding, leucine-rich repeat (NB-LRR) encoding gene family are present at the Yrr3 locus, whereas genes of this family were not identified at the Yrr1 locus. While it has been proposed that resistance to adapted and non-adapted pathogens are inherently different, the observation of (1) a simple genetic architecture of colonization resistance, (2) isolate specificity of major and minor effect QTLs, and (3) NB-LRR encoding genes at the Yrr3 locus suggest that factors associated with resistance to adapted pathogens are also critical for non-adapted pathogens.

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Dissecting the Control of Flowering Time in Grasses Using Brachypodium distachyon

Cited by 17 publications

References 63 publications

Evolution of VRN2/Ghd7-Like Genes in Vernalization-Mediated Repression of Grass Flowering

Evolution of VRN2/Ghd7-Like Genes in Vernalization-Mediated Repression of Grass Flowering

Genetic Architecture of Flowering-Time Variation in Brachypodium distachyon

The genetic architecture of colonization resistance in Brachypodium distachyon to non-adapted stripe rust (Puccinia striiformis) isolates

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