Alteration in the balance between ABA and GA signaling mediates genetic variation in induction and retention of dormancy during seed maturation in wheat

Induction and retention of dormancy are among the physiological processes that take place during seed maturation; however, the molecular mechanisms underlying these events are poorly understood in wheat. This study revealed that seed maturation in wheat is associated with decreases in abscisic acid (ABA) and gibberellin (GA) levels irrespective of dormancy level exhibited by the seeds mainly via expression of specific ABA (TaCYP707A1) and GA (TaGA3ox2, TaGA2ox3 and TaGA2ox6) metabolism genes. Consistently, ABA to GA level ratio decreased during maturation in both highly dormant and low-dormant seeds with no apparent difference in the ratio of their levels between the two seed samples. Our data, however, showed a close association between the induction and retention of dormancy during seed maturation and modulation of the balance between ABA and GA signaling via expression of specific genes that acts as positive regulators seed response to ABA (TaPYL5 and TaABI5) and GA (TaGAMyb). Consistently, the highly dormant and low-dormant seeds exhibited substantial variation in their sensitivity to ABA and GA during their maturation. The findings of this study highlight that genetic variation in induction and retention of dormancy during wheat seed maturation can be mediated by a shift in balance between seed sensitivity to ABA and GA independent of a shift in balance between their levels.