Transcriptome Analysis of the Vernalization Response in Barley (Hordeum vulgare) Seedlings

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.

Interaction of Photoperiod and Vernalization Determines Flowering Time of Brachypodium distachyon

“…During cold treatments of 1 to 4 weeks, seedlings rarely emerged from the soil, but with longer cold treatments, the coleoptile typically emerged, as commonly observed in other cereals such as barley (Sasani et al, 2009;Greenup et al, 2010Greenup et al, , 2011. During the longest cold treatments, seedlings typically reached the first leaf stage, with the second leaf visible but not fully expanded.…”

Evidence for an Early Origin of Vernalization Responsiveness in Temperate Pooideae Grasses

“…To test this prediction, we generated flowering data for representative taxa of cool-season Pooideae grasses and reconstructed vernalization responsiveness across the subfamily. Additionally, we leveraged genetic data on economically important crop species (Takahashi and Yasuda, 1971;Heide, 1994;Trevaskis et al, 2003;Yan et al, 2003;Preston and Kellogg, 2008;Greenup et al, 2011;Ream et al, 2014) to determine if orthologs of the vernalization gene VRN1, and the floral integrator VRN3, are cold responsive across the diversity of Pooideae. Our findings demonstrate that vernalization responsiveness is widespread in Pooideae and probably evolved early in the subfamily.…”

“…During this time, it is hypothesized that Pooideae became more cold tolerant (Sandve et al, 2008(Sandve et al, , 2011Sandve and Fjellheim, 2010;Preston and Sandve, 2013;Vigeland et al, 2013) and evolved a response to vernalization (Preston and Kellogg, 2008;Ream et al, 2012). Indeed, vernalization responsiveness has been identified in several so-called core group Pooideae (Davis and Soreng, 1993), such as wheat (Triticum aestivum), barley (Hordeum vulgare), oats (Avena sativa), and ryegrass (Lolium perenne), and a species sister to core Pooideae, Brachypodium distachyon (Brachypodieae; Takahashi and Yasuda, 1971;Heide, 1994;Trevaskis et al, 2003;Yan et al, 2003;Preston and Kellogg, 2008;Greenup et al, 2011;Ream et al, 2014). However, it is unknown whether vernalization responsiveness evolved at the base of the entire Pooideae, concomitant with the tropical to temperate zone transition.…”

Optimal Regulation of the Balance between Productivity and Overwintering of Perennial Grasses in a Warmer Climate

“…After short-term cold exposure, when the expression level of VRN1 is still very low, Oliver et al [120] found similar kinetics in the initial transcription of VRN1 and COR14B upon cold exposure (24 h) in barley. Under short photoperiods, high COR14B expression or positive correlation between expression of VRN1 and COR14B remained after long-term cold treatment in T. monococcum [112], barley [121], and meadow fescue [105]. COR14B is induced by CBFs, and barley VRN1 also has a putative CBF binding site in its promoter [122].…”