Biochemistry of the insect epicuticle degradation by entomopathogenic fungi

NICOLÁS PEDRINI, MARTA PATRICIA JUÁREZ, ROSANA CRESPO

COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. C, COMPARATIVE PHARMACOLOGY AND TOXICOLOGY.

Elsevier

Lugar: Nueva York; Año: 2007 vol. 146C p. 124 - 137

0742-8413

Abstract The biochemical interaction between fungal pathogens and their insect host epicuticle was studied by examining fungal hydrocarbon degrading ability. As a contact insecticide, entomopathogenic fungi invade their host through the cuticle, covered by an outermost lipid layer mainly composed of highly stable, very long chain structures. Strains of Beauveria bassiana and Metharizium anisopliae (Deuteromycotina: Hyphomycetes), pathogenic both to the blood-sucking bug Triatoma infestans (Hemiptera: Reduviidae) and the bean-weevil Acanthoscelides obtectus (Coleoptera, Bruchidae), were grown on different carbon sources. Alkane-grown cells showed a lipid pattern different from that of glucose-grown cells, evidenced by a major switch in the triacylglycerol and sterol components. Radiolabelled hydrocarbons were used to investigate the catabolic pathway and the by-product incorporation into fungal cellular components. The first oxidation round is presumably carried out by a cytochrome P450 enzyme system, the metabolites will traverse the peroxisomal membrane, and, after successive transformations will eventually provide the appropriate fatty acyl CoA for complete degradation in the peroxisomes, the site of b-oxidation in fungi. In this review we will show the relationship between fungal ability to catabolize very long chain hydrocarbons and virulence parameters. Keywords: Beauveria bassiana; Metharizium anisopliae; biological control; insect hydrocarbons; alkane degradation; cuticle; lipid metabolism; virulence enhancement.