Recently, the Innovation Team of Agricultural Microbial Resources at the Institute of Agricultural Resources and Regional Planning (IARRP), Chinese Academy of Agricultural Sciences (CAAS),  made new progress in elucidating the functional mechanisms of core bacterial effector proteins. The findings were published in Plant Biotechnology Journal under the title "Ralstonia solanacearum acetyltransferase RipU hijacks SlJAR1 to inhibit jasmonic acid signaling and facilitate pathogen infection."

Effector proteins play critical roles in mediating interactions between bacterial pathogens and their hosts; however, how core effector proteins dominate plant–microbe interactions remains poorly understood. Building on a core effector protein, RipU, previously identified by the research team, this study demonstrates that RipU suppresses pattern-triggered immunity (PTI) induced by microbe-associated molecular patterns and induces host cell death. Stable expression of RipU in plants was shown to inhibit PTI responses and reduce plant disease resistance.

Transcriptomic analyses revealed that RipU suppresses the expression of genes associated with jasmonic acid (JA) biosynthesis. Further investigation demonstrated that RipU functions as a non-canonical acetyltransferase, acetylating SlJAR1, a key enzyme in JA biosynthesis, thereby inhibiting the accumulation of bioactive JA conjugates. Based on AlphaFold3 structural predictions combined with biochemical validation, amino acid residues 203–205 of RipU were identified as critical sites for its acetyltransferase activity; mutations at these residues significantly weakened RipU-mediated acetylation of SlJAR1. Genetic analyses further indicated that this region is also essential for RipU's role in regulating plant immunity.

This study reveals a new mechanism by which a core effector protein targets plant hormone signaling, providing new theoretical insights into plant disease resistance and immune regulation.

Figure 1. Mechanistic analysis of the effector protein RipU targeting jasmonic acid biosynthesis

Figure 2. Schematic model of the mode of action of the effector protein RipU

Tong Qin of Guangxi University, Cong Shen of IARRP, and Liang Xiu'an, a graduate student at Guangxi University, are co–first authors. Professor Wei-Lei Wei, Chief Scientist of the Agricultural Microbial Resources Team at IARRP, and Dr. Zhang Xiaoxiao of Guangxi University served as co–corresponding authors. Professor He Yongqiang and Dr. Yang Shanshan of Guangxi University contributed to part of the research.

This work was supported by the National Key Laboratory of Efficient Utilization of Arid and Semi-Arid Farmland, the National Natural Science Foundation of China, the Guangxi Natural Science Foundation, the Guangxi Science and Technology Program, and the Beijing Innovation Team for Specialty Crops under the Modern Agricultural Industry Technology System.

Article link: https://onlinelibrary.wiley.com/doi/10.1111/pbi.70522