A pair of E3 ubiquitin ligases modulate immunity and flowering by targeting different ELF3 proteins in rice

The ubiquitin-proteasome system (UPS) plays crucial roles in cellular processes including plant growth, development, and stress responses. In this study, we report that a pair of E3 ubiquitin ligases APIP6 and IPI1 intricately target ELF3 paralogous proteins to regulate rice immunity and flowering. APIP6 forms homo-oligomers, or hetero-oligomers with IPI1. Both proteins interact with OsELF3-2, promoting its degradation to positively regulate resistance against the rice blast fungus (Magnaporthe oryzae). Intriguingly, overexpression of IPI1 in Nipponbare caused significantly late-flowering phenotypes similar to oself3-1 mutant. Except for late flowering, oself3-1 enhances resistance against M. oryzae. IPI1 also interacts with and promotes the degradation of OsELF3-1, a paralog of OsELF3-2. Notably, IPI1 and APIP6 synergistically modulate OsELF3s degradation, finely tuning blast disease resistance by targeting OsELF3-2, while IPI1 regulates both disease resistance and flowering by targeting OsELF3-1. This study unravels novel functions for a pair of E3 ligases in rice.