Enzymes of Entomopathogenic Fungi, Advances and Insights

Abstract

Entomopathogenic fungi (EF) are recognized biological control agents of insects. Basically, the entomopathogenic fungi pathogen activity depends on the ability of its enzymatic equipment, consisting of lipases, proteases and chitinases, which are in charge of breaking down the insect’s integument. Lipases are the first enzymes synthesized by the entomopathogenic fungi. Recently, a cytochrome P450 subfamily, referred as CYP52XI and MrCYP52 has been identified in Beauveria bassiana and Metarhizium robertsii, respectively. These break down long-chain alkenes and fatty acids to become initial nutrients. Subsequently, subtilisin type (Pr1) proteases sintetize; these enzymes are considered as virulence indicators and they are regulated by a signal transduction mechanism activated by the protein kinase A (PKA) mediated by AMPc. Through the employment of genetic engineering, it has been possible to increase virulence producing Pr1 recombinants with Androctonus australis neurotoxins or with chitinases, reducing the insect’s time of death. In the course of time, the Pr1 protease gene has presented evolutionary adaptations by gene duplication or horizontal transfer infecting different orders of insects. In the same way, the entomopathogenic fungi chitinases have presented a functional diversification. Currently, these have been phylogenetically classified into three subgroups, in accordance to the catalytic site domain and the chitin binding domain. The chitinolytic activity has increased through a directed evolution processes and genetic recombination with Bombyx mori chitinase. Recently, enzymes have been employed as control agents for insects and phytopathogenic fungi (disease originator) opening new potentialities in order to improve the entomopathogenic fungi use. Solid state fermentation is a bioprocess that would produce at great scale enzymes and some other metabolites in grade of increasing the entomopathogenic fungi virulence, in the control of insects and potentially in some diseases affecting plants.