A zinc finger suppressor involved in stress resistance, cell wall integrity, conidiogenesis, and autophagy in the necrotrophic fungal pathogen Alternaria alternata

The tangerine pathotype of Alternaria alternata can withstand high-level reactive oxygen species (ROS). By analyzing loss- and gain-of-function mutants, this study demonstrated that a Cys2His2 zinc finger-containing transcription regulator, A. alternata Stress Response Regulator 1 (AaSRR1), plays a...

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Bibliographic Details
Published in:Microbiological research 2022-10, Vol.263, p.127106-127106, Article 127106
Main Authors: Lu, Hsin-Yu, Huang, Yu-Ling, Wu, Pei-Ching, Wei, Xian-Yong, Yago, Jonar I., Chung, Kuang-Ren
Format: Article
Language:English
Subjects:
Autophagy
Detoxification
ROS
Starvation
Suppressor
Zinc finger
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Summary:The tangerine pathotype of Alternaria alternata can withstand high-level reactive oxygen species (ROS). By analyzing loss- and gain-of-function mutants, this study demonstrated that a Cys2His2 zinc finger-containing transcription regulator, A. alternata Stress Response Regulator 1 (AaSRR1), plays a negative role in resistance to peroxides and singlet-oxygen-generating compounds. AaSRR1 plays no role in cellular susceptibility or resistance to superoxide-producing compounds. AaSRR1 also negatively regulates conidiogenesis, maintenance of cell wall and membrane integrities, and chitin biosynthesis. Some wild-type hyphae displayed necrosis after exposure to 30 mM H2O2, whereas AaSRR1 deficient mutant (ΔAaSRR1) hyphae had visible granules and vacuoles. sGFP-AaATG8 proteolysis assays revealed that H2O2 and starvation could trigger autophagy formation in both wild type and ΔAaSRR1. Autophagy occurred at higher rates in ΔAaSRR1 than wild type under both conditions, particularly after H2O2 treatments, indicating that autophagy might contribute to ROS resistance. Upon exposure to H2O2 or under starvation, AaSRR1 was translocated into the nucleus, even though the expression of AaSRR1 was decreased. AaSRR1 is required for vegetative growth but is dispensable for fungal virulence as assayed on detached calamondin leaves. AaSRR1 suppressed the expression of the gene encoding a HOG1 mitogen-activated protein (MAP) kinase implicated in ROS resistance. Mutation of AaSRR1 increased catalase activity but decreased superoxide dismutase activity, leading to fewer ROS accumulation in the cytosol. Nevertheless, our results indicated that AaSRR1 is a transcription suppressor for ROS resistance. This study also revealed tradeoffs between stress responses and hyphal growth in A. alternata. •The Cys2His2 zinc finger AaSRR1 negatively ROS resistance.•AaSRR1 negatively regulates the HOG1 MAP kinase.•Autophagy might contribute to ROS resistance.•This study reveals tradeoffs between stress responses and fungal growth.
ISSN:0944-5013
1618-0623
DOI:10.1016/j.micres.2022.127106