ABSTRACT
Crop floral diseases are economically important as they reduce grain yield and quality and even introduce food toxins. Rice false smut has emerged as a serious floral disease producing mycotoxins. However, very little is known on the interaction mechanisms between rice flower and the causal fungus Ustilaginoidea virens. Here we show that a conserved anti-fungal immunity in rice flower is disarmed by U. virens via a secreted protein UvChi1. UvChi1 functioned as an essential virulence factor and directly interacted with the chitin receptor CEBiP and co-receptor CERK1 in rice to disrupt their oligomerizations and subsequent immune responses. Moreover, intraspecific-conserved UvChi1 could target OsCEBiP/OsCERK1 receptor complex in at least 98.5% of 5232 surveyed rice accessions. These results demonstrate that U. virens utilizes a crucial virulence factor to subvert chitin-triggered flower immunity in most rice varieties, providing new insights into the susceptibility of rice to false smut disease.
One Sentence Summary The fungal pathogen Ustilaginoidea virens disarms chitin-triggered immunity in rice flower via a secreted chitinase.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Author for contact details: Wen-Ming Wang (Tel 86-28-86290949; fax 86-28-86290903; email j316wenmingwang{at}sicau.edu.cn), Jing Fan (Tel 86-28-86290949; fax 86-28-86290903; email fanjing13971{at}sicau.edu.cn)
Funding Information This work was supported by grants from the National Natural Science Foundation of China (31772241 and 32072503 to J.F.) and from the Science and Technology Program Project of Sichuan Province (2020YJ0145 to J.F., 2020YJ0332 to W.-M.W.).
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