Abstract

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.

中文翻译：

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MrPEX33参与罗氏沼虾的感染相关形态发生和致病性

摘要

过氧化物酶体是必不可少的细胞器，在真核生物的不同生物学过程中起着重要作用。PEX33是过氧化物酶体对接机制中一种丝状真菌特有的过氧化物酶，与其他真菌病原体的致病力和发育有关。但是，尚不清楚PEX33对于昆虫病原性真菌的致病性和发育是否必要。在本研究中，我们报告的同源物的存在PEX33，即MrPEX33（MAA_05331），在昆虫病原真菌，绿僵robertsii。一个M. robertsii表达与MrPEX33-GFP和mCherry-PTS1融合蛋白的转基因菌株表明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的导入途径。MrPEX33的靶向基因缺失导致无性孢子形成能力显着下降，并伴随着与多个与构象相关的基因的下调，例如wetA，abaA和brlA。更重要的是，我们的生物测定结果表明，Δ的毒力MrPEX33突变，对大蜡螟通过角质层感染，被大大减少。这进一步伴随着前庭的形成和表皮渗透的显着下降。此外，ΔMrPEX33突变体显示出对细胞壁完整性和氧化应激的耐受性显着降低。两者合计，我们的结果表明MrPEX33参与角质层感染相关的形态发生和致病性。

关键点

• MrPEX33是过氧化物酶体对接机制中的特定过氧化物酶。

• MrPEX33定位于过氧化物酶体，并参与基质蛋白的导入。

• MrPEX33参与与表皮感染相关的致病性。