OsCUL3a-Associated Molecular Switches Have Functions in Cell Metabolism, Cell Death, and Disease Resistance.

This study applies parallel reaction monitoring (PRM) proteomics and CRISPR-Cas9 mutagenesis to identify relationships between cell metabolism, cell death, and disease resistance. In oscul3a (oscullin3a) mutants, OsCUL3a-associated molecular switches are responsible for disrupted cell metabolism that leads to increased total lipid content in rice grain, a late accumulation of H2O2 in leaves, enhanced Xanthomonas oryzae pv. oryzae disease resistance, and suppressed panicle and first internode growth. In oscul3a mutants, PRM-confirmed upregulated molecular switch proteins include lipoxygenases (CM-LOX1 and CM-LOX2), suggesting a novel connection between ferroptosis and rice lesion mimic formation. Rice immunity-associated proteins OsNPR1 and OsNPR3 were shown to interact with each other and have opposing regulatory effects based on the cell death phenotype of osnpr1/oscul3a and osnpr3/oscul3a double mutants. Together, these results describe a network that regulates plant growth, disease resistance, and grain quality that includes the E3 ligase OsCUL3a, cell metabolism-associated molecular switches, and immunity switches OsNPR1 and OsNPR3.