ABA-activated subclass III SnRK2s control kernel maturation in maize

Seed maturation is a critical development transition and it largely affects the final yield and quality of crops. Abscisic acid (ABA)-activated sucrose-non-fermentation kinase subfamily 2 (SnRK2s) constitute a well-known regulatory network that modulate seed maturation in Arabidopsis; however, the underlying genetic and regulatory mechanisms in cereal crops remain largely unknown. Here, we found that ABA levels exhibited two distinct peaks during kernel development in maize, corresponding to the lag and maturation phase, respectively. Integrated transcriptome and proteome profiling of kernels treated with exogenous ABA at the pre-maturation stage suggested that the second peak of ABA acts as a trigger for kernel maturation program. Knockout of ZmSnRK2s demonstrated that subclass III ZmSnRK2s are required for kernel maturation in maize, and the loss-of-function of subclass III ZmSnRK2s showed a disruption in kernel dehydration and dormancy. We identified a conserved ABA–SnRK2–bZIP signaling pathway mediating this process in maize. Additionally, ZmSnRK2.10 overexpression accelerates kernel dehydration during maturity, achieving reduced kernel moisture content (KMC) at physiological maturity (PM). Overall, our findings establish ABA-activated SnRK2s as central regulators of kernel maturation in maize and provide valuable genetic resources for breeding maize varieties with low moisture content at harvest.