OsHYPK-mediated protein N-terminal acetylation coordinates plant development and abiotic stress responses in rice

N-terminal acetylation is one of the most common protein modifications in eukaryotes, and approxi-mately 40% of human and plant proteomes are acetylated by ribosome-associated N-terminal acetyl-transferase A (NatA) in a co-translational manner. However, the in vivo regulatory mechanism of NatA and the global impact of NatA-mediated N-terminal acetylation on protein fate remain unclear. Here, we identify Huntingtin Yeast partner K (HYPK), an evolutionarily conserved chaperone-like protein, as a positive regulator of NatA activity in rice. We found that loss of OsHYPK function leads to develop-mental defects in rice plant architecture but increased resistance to abiotic stresses, attributable to perturbation of the N-terminal acetylome and accelerated global protein turnover. Furthermore, we demonstrated that OsHYPK is also a substrate of NatA and that N-terminal acetylation of OsHYPK pro-motes its own degradation, probably through the Ac/N-degron pathway, which could be induced by abiotic stresses. Taken together, our findings suggest that the OsHYPK-NatA complex plays a critical role in coordinating plant development and stress responses by dynamically regulating NatA-mediated N-terminal acetylation and global protein turnover, which are essential for maintaining adaptive pheno-typic plasticity in rice.

Automated summary

This study identifies HYPK as a positive regulator of NatA activity in rice and demonstrates the critical role of the OsHYPK-NatA complex in coordinating plant development and stress responses.