UvWhi2 Is Required for Stress Response and Pathogenicity in Ustilaginoidea virens

doi:10.1016/j.rsci.2021.12.004

Abstract

Abstract:

Some stress response-related genes have been identified in Ustilaginoidea virens, but it is not clear whether and how defects of stress responses affect the pathogenesis processes of U. virens. In this study, we identified a general stress response factor UvWHI2 as a homolog of Saccharomyces cerevisiae Whi2 in U. virens. The relative expression level of UvWhi2 was significantly up-regulated during infection, suggesting that UvWHI2 may be involved in pathogenesis. Furthermore, knockout of UvWhi2 showed decreased mycelial growth, increased conidiation in the potato sucrose medium and a defect in pathogenicity. In addition, the RNA-Seq and phenotypic analysis showed that UvWHI2 was involved in response to oxidative, hyperosmotic, cell wall stress and nutrient limitation. Further studies revealed that the defects of stress responses of the ∆Uvwhi2 mutant affected the formation of secondary spores on the nutrient limited surface and the rice surface, resulting in a significant reduction of pathogenicity of U. virens. Our results suggest that UvWHI2 is necessary for fungal growth, stress responses and the formation of secondary spores in U. virens. In addition, the defects of stress responses can affect the formation of secondary spores on the rice surface, and then compromise the pathogenicity of U. virens.

Key words: Whi2, rice false smut, Ustilaginoidea virens, pathogenesis, secondary spore

Meng Shuai, Qiu Jiehua, Xiong Meng, Liu Zhiquan, Jane Sadhna Jagernath, Lin Fucheng, Shi Huanbin, Kou Yanjun. UvWhi2 Is Required for Stress Response and Pathogenicity in Ustilaginoidea virens[J]. Rice Science, 2022, 29(1): 47-54.

Figures/Tables 3

Fig. 1. Deletion of UvWhi2 results in decreased vegetative growth and increased conidiation in U. virens. A and B, Mycelium growth (A) and colony morphology (B) of the wild type (WT), UvWhi2 gene deletion mutants (∆Uvwhi2-39 and ∆Uvwhi2-43) and complementation strain (∆Uvwhi2-C-9) on the potato sucrose agar medium in dark at 28 ºC for 15 d. C, Dry weight of mycelia was measured in the liquid potato sucrose medium after 7 d culture. D and E, Knockout of UvWhi2 enhanced conidiation under nutrient-rich condition. Data in B-D are Mean ± SD (n = 3). ***, Significant difference at the 0.001 level by the Duncan’s test.

Fig. 2. UvWHI2 is required for pathogenesis in U. virens. A, Disease symptoms of wild type (WT), UvWhi2 deletion mutants (∆Uvwhi2-39 and ∆Uvwhi2-43) and complementation (∆Uvwhi2-C-9) strains on the rice panicles of Wanxian 98 at 21 d post inoculation. The red arrows show the false smut balls. B, Statistical analysis of the average number of false smut balls on the inoculated panicles. Data are Mean ± SD (n = 3). ***, Significant difference at the 0.001 level by the Duncan’s test.

Fig. 3. Conidial germination of U. virens in wild type (WT), ∆Uvwhi2 mutants (∆Uvwhi2-39 and ∆Uvwhi2-43) and complementation strain (∆Uvwhi2-C-9) on potato sucrose agar (PSA, A), agarose plates (B) and rice sheath (C) at 28 ºC for 3 d.

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