Peroxins in Peroxisomal Receptor Export System Contribute to Development, Stress Response, and Virulence of Insect Pathogenic Fungus Beauveria bassiana.

Abstract

In filamentous fungi, recycling of receptors responsible for protein targeting to peroxisomes depends on the receptor export system (RES), which consists of peroxins Pex1, Pex6, and Pex26. This study seeks to functionally characterize these peroxins in the entomopathogenic fungus Beauveria bassiana. BbPex1, BbPex6, and BbPex26 are associated with peroxisomes and interact with each other. The loss of these peroxins did not completely abolish the peroxisome biogenesis. Three peroxins were all absolutely required for PTS1 pathway; however, only BbPex6 and BbPex26 were required for protein translocation via PTS2 pathway. Three gene disruption mutants displayed the similar phenotypic defects in assimilation of nutrients (e.g., fatty acid, protein, and chitin), stress response (e.g., oxidative and osmotic stress), and virulence. Notably, all disruptant displayed significantly enhanced sensitivity to linoleic acid, a polyunsaturated fatty acid. This study reinforces the essential roles of the peroxisome in the lifecycle of entomopathogenic fungi and highlights peroxisomal roles in combating the host defense system.