Wang Zhangxun, Feng Jianyu, Jiang Yuanyuan, Xu Xiuzhen, Xu Liuyi, Zhou Quan, Huang Bo
Anhui Provincial Key Laboratory of Microbial Pest Control, Anhui Agricultural University, Hefei, 230036, China.
Key Laboratory of Biology and Sustainable Management of Plant Diseases and Pests of Anhui Higher Education Institutes, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, China.
Appl Microbiol Biotechnol. 2021 Feb;105(3):1079-1090. doi: 10.1007/s00253-020-11071-3. Epub 2021 Jan 14.
Peroxisomes, being indispensable organelles, play an important role in different biological processes in eukaryotes. PEX33, a filamentous fungus-specific peroxin of the docking machinery of peroxisomes, is involved in the virulence and development of other fungal pathogens. However, it is not clear whether PEX33 is necessary for the pathogenicity and development of an insect pathogenic fungus. In the present study, we report the presence of homologs of PEX33, namely MrPEX33 (MAA_05331), in the entomopathogenic fungus, Metarhizium robertsii. An M. robertsii transgenic strain expressing the fusion protein with MrPEX33-GFP and mCherry-PTS1 showed that MrPEX33 localizes to peroxisomes. The results also demonstrated that MrPEX33 is involved in the peroxisomal import pathway by peroxisomal targeting signals. Targeted gene deletion of MrPEX33 led to a significant decline in the asexual sporulation capacity, which was accompanied by downregulation of several conidiation-associated genes, such as wetA, abaA, and brlA. More importantly, our bioassay results showed that the virulence of ∆MrPEX33 mutants, against Galleria mellonella through cuticle infection, was greatly reduced. This was further accompanied by a significant drop in appressorium formation and cuticle penetration. Additionally, ∆MrPEX33 mutants showed a significant decrease in tolerance to cell wall integrity and oxidative stress. Taken together, our results suggest that MrPEX33 is involved in the cuticle infection-related morphogenesis and pathogenicity. KEY POINTS: • MrPEX33 is a specific peroxin of the docking machinery of peroxisomes. • MrPEX33 localizes to peroxisomes and is involved in the import of matrix proteins. • MrPEX33 is involved in the pathogenicity associated with cuticle infections.
过氧化物酶体作为不可或缺的细胞器，在真核生物的不同生物学过程中发挥着重要作用。PEX33是过氧化物酶体对接机制中丝状真菌特有的过氧化物酶，参与其他真菌病原体的毒力和发育。然而，尚不清楚PEX33对于昆虫病原真菌的致病性和发育是否必要。在本研究中，我们报道了昆虫病原真菌球孢白僵菌中存在PEX33的同源物，即MrPEX33（MAA_05331）。表达MrPEX33-GFP和mCherry-PTS1融合蛋白的球孢白僵菌转基因菌株表明，MrPEX33定位于过氧化物酶体。结果还表明，MrPEX33通过过氧化物酶体靶向信号参与过氧化物酶体导入途径。对MrPEX33进行靶向基因缺失导致无性孢子形成能力显著下降，同时伴有几个与产孢相关基因（如wetA、abaA和brlA）的下调。更重要的是，我们的生物测定结果表明，通过体表感染，∆MrPEX33突变体对大蜡螟的毒力大大降低。这还伴随着附着胞形成和体表穿透的显著下降。此外，∆MrPEX33突变体对细胞壁完整性和氧化应激的耐受性显著降低。综上所述，我们的结果表明MrPEX33参与了与体表感染相关的形态发生和致病性。要点：•MrPEX33是过氧化物酶体对接机制的特异性过氧化物酶。•MrPEX33定位于过氧化物酶体并参与基质蛋白的导入。•MrPEX33参与与体表感染相关的致病性。
