Huazhong Agricultural University revealed the molecular mechanism of Bacillus subtilis protease secreted by Aspergillus oryzae inhibiting rice immunity
By: Date: 2022-07-25 Categories: foodtechnology Tags: ,
Recently, Professor huangjunbin’s team from the school of plant science and technology of Huazhong Agricultural University published a research paper on plant Physics Online entitled”a secret fungal subtitle interferences with rice immunity via degradation of supplier of G2 all of Skp1″, which revealed the molecular mechanism of subtilisin secreted by Aspergillus oryzae to target degrade the positive regulator of broad-spectrum disease resistance of rice ossgt1 to inhibit host resistance.
 
Rice false smut is one of the major diseases in rice production. In China, rice false smut is particularly serious, causing an average annual loss of 250million kg of rice, and the produced rice false smut toxin is potentially toxic to animal cells and organs, seriously threatening China’s food security. Cultivating and utilizing disease resistant varieties is the most economical and effective means to prevent and control crop diseases and maintain the sustainable development of green agriculture. However, at this stage, there is a serious lack of Rice False Smut resistant varieties and genetic resources, and no available natural resistance source has been found. Therefore, in-depth analysis of the infection mechanism of Rice False Smut and its interaction mechanism with rice can provide theoretical basis and important resources for the genetic improvement of rice varieties resistant to rice false smut. Subtilisin is an important serine protease, which widely exists in eukaryotes and prokaryotes and participates in a variety of biological functions. Previous studies have shown that subtilisin in pathogenic fungi is related to the growth, sporulation, autophagy, lipid metabolism and pathogenicity of the pathogen itself; However, the molecular regulation mechanism of subtilisin in the interaction between pathogenic bacteria and plants is still unclear.
 
The results showed that the expression of subtilisin uvpr1a secreted by Aspergillus oryzae was significantly up-regulated at different stages of floral colonization, and the knockout of uvpr1a could significantly reduce the pathogenicity of Aspergillus oryzae; Further studies showed that uvpr1a is a virulence effector protein localized in plant cytoplasm, which can inhibit Bax induced plant cell death. Exogenous expression of uvpr1a in rice reduced the resistance of rice to rice false smut, rice blast, rice sheath blight and rice bacterial wilt, while host induced gene silencing targeting uvpr1a enhanced the resistance of rice. Through screening library and a series of interaction experiments, it was found that uvpr1a interacted with ossgt1 (supplier of G2 allele of Skp1), an important immune regulator in rice, in plant cytoplasm; Partial knockout of ossgt1 resulted in the weakening of rice resistance to rice false smut, rice blast, rice sheath blight and rice bacterial wilt. Overexpression of ossgt1 could significantly improve the broad-spectrum disease resistance of rice. In vivo and in vitro experiments confirmed that uvpr1a protein can directly degrade rice ossgt1 protein, and the content of ossgt1 protein in heterologous expression of uvpr1a rice decreased. This study revealed the molecular mechanism of the targeted degradation of the rice immune regulator ossgt1 by subtilisin uvpr1a secreted by Aspergillus oryzae, thereby inhibiting host resistance. It was found that ossgt1 has the potential to genetically improve rice resistance to Rice False Smut and broad-spectrum resistance.
 
Chen Xiaoyang, a doctoral student of the school of plant science and technology, and Li XiaBing, a master student, are the co first authors of the paper, and Associate Professor Zheng Lu is the corresponding author. Professor Huang Junbin, Professor Luo Chaoxi, Professor Chen Xiaolin, Professor Xie Kabin, Professor Li Guotian, Associate Professor Liu Hao, Associate Professor Yin Weixiao, doctoral student Duan Yuhang, master student Pei Zhangxin, and Professor Tom Hsiang of Guelph University in Canada participated in this work. The research was supported by the National Natural Science Foundation of China, the key project of Hubei provincial key research and development plan, and the independent scientific and technological innovation fund of central China Agricultural University.
 
[English Abstract]
 
  Serine protease subtilase, found widely in both eukaryotes and prokaryotes, participates in various biological processes. However, how fungal subtilase regulates plant immunity is a major concern. Here, we identified a secreted fungal subtilase, UvPr1a, from the rice false smut (RFS) fungus Ustilaginoidea virens. We characterized UvPr1a as a virulence effector localized to the plant cytoplasm that inhibits plant cell death induced by Bax. Heterologous expression of UvPr1a in rice (Oryza sativa) enhanced plant susceptibility to rice pathogens. UvPr1a interacted with the important rice protein OsSGT1 (SUPPRESSOR OF G2 ALLELE OF skp1), a positive regulator of innate immunity against multiple rice pathogens, degrading OsSGT1 in a protease activity–dependent manner. Furthermore, host-induced gene silencing of UvPr1a compromised disease resistance of rice plants. Our work reveals a previously uncharacterized fungal virulence strategy in which a fungal pathogen secretes a subtilase to interfere with rice immunity through degradation of OsSGT1, thereby promoting infection. These genetic resources provide tools for introducing RFS resistance and further our understanding of plant-pathogen interactions.
 
Paper link:https://academic.oup.com/plphys/advance-article/doi/10.1093/plphys/kiac334/6647860?searchresult=1