A novel micropeptide regulates kernel dehydration in maize through ethylene signaling

Kernel dehydration rate (KDR) is a critical factor affecting mechanized maize harvesting and kernel quality. Despite its agricultural importance, the molecular mechanisms regulating KDR remain unclear. Previous studies have identified several QTLs controlling KDR, but their functional characterization has been limited. Yu et al.  investigate the genetic regulation of KDR by focusing on qKDR1, a major QTL that influences kernel moisture content at harvest. The study reveals that qKDR1 regulates the expression of qKDR1 REGULATED PEPTIDE GENE (RPG), which encodes microRPG1, a 31-amino acid Zea genus-specific micropeptide that originated de novo from a non-coding sequence. The authors demonstrate that microRPG1 modulates kernel dehydration by precisely regulating ZmETHYLENE-INSENSITIVE3-like 1 and 3 (ZmEIL1 and ZmEIL3), key components of the ethylene signaling pathway. Loss-of-function mutations in microRPG1 result in accelerated kernel dehydration, whereas overexpression or exogenous application of the micropeptide delays dehydration in both maize and Arabidopsis thaliana. This suggests that microRPG1 functions as a negative regulator of KDR by suppressing ethylene signaling. This study enhances our understanding of maize kernel dehydration and identifies microRPG1 as a key regulator of this process. Modulating its expression could help develop maize varieties with improved dehydration rates, benefiting mechanized harvesting and reducing post-harvest drying cost. (Summary by Muhammad Aamir Khan @MAKNature1998) Cell 10.1016/j.cell.2024.10.030