Genetic variation of seed dormancy in wheat (Triticum aestivum L.) is mediated by transcriptional regulation of abscisic acid metabolism and signaling.

Abscisic acid (ABA) regulates seed dormancy and therefore preharvest sprouting (PHS) in wheat. This study investigated the contribution of transcriptional regulation of ABA metabolism and signaling genes to genetic variation in dormancy of wheat seeds. Our results showed that genetic variation in seed dormancy is highly correlated with ABA content (r > 0.86), which, in turn, was closely associated with the expression levels of ABA biosynthesis genes, TaNCED1 (r = 0.78) and TaNCED2 (r = 0.67). A relatively lower correlation was observed between ABA content and the expression levels of ABA catabolism genes, TaCYP707A1 (r = 0.51) and TaCYP707A2 (r = 0.57). The expression level of TaABI5 exhibited strong associations with the levels of ABA (r = 0.8) and seed dormancy (r > 0.9), indicating the importance of seed ABA sensitivity in mediating genetic variation in dormancy. Furthermore, high positive correlations were prevalent between the expression patterns of TaABI5 and TaNCED1 (r = 0.91) or TaNCED2 (r = 0.82). Overall, our results implicated the significance of TaNCEDs and TaABI5 in regulating genetic variation in ABA level and sensitivity and thereby seed dormancy, highlighting the potential use of these genes to develop molecular markers for incorporating PHS resistance in wheat.