U-box E3 ubiquitin ligase OsPUB41 represses rice blast resistance by promoting degradation of OsPALs.

Plant U-box (PUB) proteins, the smallest E3 ubiquitin ligase subfamily, play key roles in plant growth, development, and responses to biotic/abiotic stresses. However, their functions in rice immunity remain largely unexplored. Here, we identified Oryza sativa plant U-box 41 (OsPUB41) as a blast-induced PUB gene via transcriptome analysis and quantitative polymerase chain reaction detection. And the role of OsPUB41 in blast resistance was investigated using both OsPUB41 knockout and over-expression transgenic plants. OsPUB41 functions as an active E3 ligase, promoting the degradation of Oryza sativa phenylalanine ammonia-lyase 1 (OsPAL1) and its homologous proteins, which are key enzymes in lignin biosynthesis, via the ubiquitin-proteasome system. Knocking out OsPUB41 elevated OsPALs protein levels, increased lignin accumulation, and strengthened cell walls, thereby limiting Magnaporthe oryzae invasion. Consequently, OsPUB41 knockout enhanced resistance to rice blast without yield penalty, whereas OsPUB41 over-expression reduced resistance to rice blast. Our study uncovers a novel PUB-mediated immune mechanism in rice and proposesOsPUB41 as a potential target for (CRISPR/Cas9)-mediated genome editing, which may facilitate the development of blast-resistant rice without compromising agronomic traits.