AUTHOR=Li Guo-Bang , Fan Jing , Wu Jin-Long , He Jia-Xue , Liu Jie , Shen Shuai , Gishkori Zeeshan Ghulam Nabi , Hu Xiao-Hong , Zhu Yong , Zhou Shi-Xin , Ji Yun-Peng , Pu Mei , Zhao Jing-Hao , Zhao Zhi-Xue , Wang He , Zhang Ji-Wei , Huang Yan-Yan , Li Yan , Huang Fu , Wang Wen-Ming 

TITLE=The Flower-Infecting Fungus Ustilaginoidea virens Subverts Plant Immunity by Secreting a Chitin-Binding Protein

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.733245

DOI=10.3389/fpls.2021.733245

ISSN=1664-462X

ABSTRACT=<p><italic>Ustilaginoidea virens</italic> is a biotrophic fungal pathogen specifically colonizing rice floral organ and causes false smut disease of rice. This disease has emerged as a serious problem that hinders the application of high-yield rice cultivars, by reducing grain yield and quality as well as introducing mycotoxins. However, the pathogenic mechanisms of <italic>U. virens</italic> are still enigmatic. Here we demonstrate that <italic>U. virens</italic> employs a secreted protein UvCBP1 to manipulate plant immunity. <italic>In planta</italic> expression of <italic>UvCBP1</italic> led to compromised chitin-induced defense responses in <italic>Arabidopsis</italic> and rice, including burst of reactive oxygen species (ROS), callose deposition, and expression of defense-related genes. <italic>In vitro</italic>-purified UvCBP1 protein competes with rice chitin receptor OsCEBiP to bind to free chitin, thus impairing chitin-triggered rice immunity. Moreover, <italic>UvCBP1</italic> could significantly promote infection of <italic>U. virens</italic> in rice flowers. Our results uncover a mechanism of a floral fungus suppressing plant immunity and pinpoint a universal role of chitin-battlefield during plant–fungi interactions.</p>