The Innovation Team of Agricultural Microbial Resources of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) revealed the functional mechanism of the type Ⅲ secretion component HrpP in regulating plant immunity.

Related results were published on Microbiology Spectrum, a well-known academic journal of the American Society for Microbiology.

The type III secretion system (T3SS) is an important protein export apparatus of bacteria, which has ca. 30 kb including approximately 20 genes, and is responsible for secretion and translocation of effector proteins into host cells. In recent years, the biological function of effectors have been well documented, however, current understanding of the functional mechanisms of T3SS components is still limited.

This study showed for the first time that P. syringae pv. tomato DC3000 (Pst DC3000) T3SS component HrpP induced host cell death, suppressed pattern-triggered immunity (PTI), and partially restored effector translocation ability of the hrpP mutant. The constitutive expression of HrpP in plants could inhibit PTI and reduce the plant disease resistance. In addition, this study found that HrpP via its N terminus HrpP_1-119 interact with mitogen-activated protein kinase kinase 2 (MKK2) on the plant membrane and in the nucleus. Further studies showed that the HrpP-MKK2 interaction was associated with PTI suppression but independent of HrpP induced cell death.

This study will generate a broad understanding of the biological function and mode of action of T3SS component, and provide new insights into disease control.

Graduate student Ya Jin of the IARRP and Dr. Wei Zhang of the Cornell University are the first authors, and professor Hai-Lei Wei and Dr. Jun-Zhou Li are the corresponding authors. Professor Filiatrault of the United States Department of Agriculture and professor Qi-Guo Zhuang of the Sichuan Provincial Academy of Natural Resource Sciences also participated in the research.

This work is funded by the National Natural Science Foundation of China, the National Key R&D Program of China, and the Sichuan International S&T Cooperation Program.

Paper link: https://doi.org/10.1128/spectrum.05148-22 

The mechanism of the T3SS component HrpP [Photo/IARRP]