The entomopathogenic fungus Beauveria bassiana produces microsclerotia‐like pellets mediated by oxidative stress and peroxisome biogenesis

Abstract

Summary Several filamentous fungi are known to produce macroscopic pigmented hyphal aggregates named sclerotia. In recent years, some entomopathogenic fungi were reported to produce small sclerotia termed ‘microsclerotia’, becoming new potential propagules for biocontrol strategies. In this study, we described the production of microsclerotia‐like pellets by the entomopathogenic fungus Beauveria bassiana. The carbon: nitrogen ratio equal to or higher than 12.5:1 amended with Fe2+ induced the germination of conidia, producing hyphal aggregate that formed sclerotial structures in submerged liquid cultures. These aggregates were able to tolerate desiccation as they germinated and subsequently produced viable conidia. Conidia derived from microsclerotial aggregates formulated with diatomaceous earth effectively kill Tribolium castaneum larvae. Optical and transmission microscopical imaging, qPCR and spectrophotometric analysis revealed that an oxidative stress scenario is involved in conidial differentiation into microsclerotia‐like pellets, inducing fungal antioxidant response with high peroxidase activity – mainly detected in peroxisomes and mitochondria – and progress with active peroxisome proliferation. The results provide clues about B. bassiana microsclerotial differentiation and indicate that these pigmented aggregates are promising propagules for production, formulation and potentially application in the control of soil‐inhabiting arthropod pests.

Different contributions of the peroxisomal import protein Pex5 and Pex7 to development, stress response and virulence of insect fungal pathogen Beauveria bassiana

“…B. bassiana assimilate variable amounts of fatty alcohols, fatty acids and wax esters in the host cuticles (Pedrini et al, 2010). When conidia develop into microsclerotia-like pellets, peroxisome proliferation as well as peroxisomal peroxidase activity is significantly enhanced (Huarte- Bonnet et al, 2019). However, the roles of peroxisome and Pex genes in physiologies of B. bassiana are still far from clear.…”

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

“…In Metarhizium robertsii (a sister entomopathogenic fungus), peroxisomal activity and peroxin genes are involved in fungal responses to oxidative stress [ 38 ]. Under submerged conditions, Woronin bodies are involved in peroxisome biogenesis and the stress response in B. bassiana during microsclerotia formation [ 10 ]. In insect hemocoel, hemolymph causes osmotic stress on fungal cells [ 39 ].…”

“…In filamentous fungi, peroxisomes have important roles in secondary metabolism [ 7 ], development [ 8 ], and pathogenicity [ 9 ]. Similarly, peroxisomes are involved in fatty-acid assimilation, stress response, development, and virulence in B. bassiana [ 10 , 11 ]. Our previous study showed the functional divergence of different peroxins and highlighted the essential roles of peroxisomes involved in biocontrol potential of the entomopathogenic fungi.…”

DISEÑO Y EVALUACIÓN DE MEDIOS LÍQUIDOS PARA LA PRODUCCIÓN DE BLASTOSPORAS DE Beauveria bassiana

“…Beauveria bassiana es una especie ampliamente distribuida, este hongo se considera ubicuo capaz de explotar una variedad de entornos, incluidos el suelo, las plantas y los insectos; puede vivir como un saprófito en el suelo, o como un entomopatógeno que afecta a una amplia gama de artrópodos (Zimmerman, 2007;Boomsma et al, 2014). B. bassiana presenta diferentes tipos de propágulos, específicamente, conidios, blastosporas y microesclerocios (Mascarin et al, 2015;Huarte-Bonnet et al, 2019). B. bassiana actualmente se comercializa como ingrediente activo en diferentes micoinsecticidas, ocupando un 33.9% del mercado aproximadamente, y son los conidios aéreos el ingrediente activo principal de estos productos (de Faria & Wraight, 2007).…”