Abstract
BackgroundUstilaginoidea virens has become one of the most devastating rice pathogens in China, as well as other rice-growing areas. Autophagy is an important process in normal cell differentiation and development among various organisms. To date, there has been no optimized experimental system introduced for the study of autophagy in U. virens. In addition, the function of autophagy in pathogenesis remains unknown in U. virens. Therefore, the functional analyses of UvAtg8 may potentially shed some light on the regulatory mechanism and function of autophagy in U. virens.ResultsIn this study, we characterized the functions of UvAtg8, which is a homolog of Saccharomyces cerevisiae ScAtg8, in the rice false smut fungus U. virens. The results showed that UvATG8 is essential for autophagy in U. virens. Also, the GFP-UvATG8 strain, which could serve as an appropriate marker for monitoring autophagy in U. virens, was generated. Furthermore, this study found that the ΔUvatg8 mutant was defective in the vegetative growth, conidiation, adaption to oxidative, hyperosmotic, cell wall stresses, and production of toxic compounds. Pathogenicity assays indicated that deletion of UvATG8 resulted in significant reduction in virulence of U. virens. Further microscopic examinations of the infection processes revealed that the severe virulence defects in the ∆Uvatg8 were mainly caused by the highly reduced conidiation and secondary spore formation.ConclusionsOur results indicated that the UvAtg8 is necessary for the fungal growth, stresses responses, conidiation, secondary spore formation, and pathogenicity of U. virens. Moreover, our research finding will potentially assist in further clarifying the molecular mechanism of U. virens infection, as well as provide a good marker for autophagy in U. virens and a good reference value for the further development of effective fungicides based on gene targeting.
Highlights
Rice false smut disease is caused by the ascomycete fungal pathogen Ustilaginoidea virens
Our results indicated that UvAtg8 mediated autophagy played important roles in the growth, stresses responses, production of toxic compounds, conidiation, secondary spore formation, and pathogenicity of U. virens
Identification of UvAtg8 To identify the Atg8 homologous protein in U. virens, the amino acid sequence of Atg8 (GenBank KZV12988) from Saccharomyces cerevisiae was used as a query for the BLASTP search on NCBI
Summary
Rice false smut disease is caused by the ascomycete fungal pathogen Ustilaginoidea virens. It is currently one of the most devastating rice fungal diseases in China, as well as many other countries (Fan et al 2016; Jia et al 2014; Ladhalakshmi et al 2012; Nessa et al 2015; Qiu et al 2019). It has been found that the rice false smut disease is difficult to control. It is more and more important to deepen the understanding of the pathogenic mechanism of U. virens in order to provide clues for the development of more effective strategies to control the disease. The functional analyses of UvAtg may potentially shed some light on the regulatory mechanism and function of autophagy in U. virens
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