Identification of Exoenzymes Secreted by Entomopathogenic Fungus Beauveria pseudobassiana RGM 2184 and Their Effect on the Degradation of Cocoons and Pupae of Quarantine Pest Lobesia botrana

Abstract

Beauveria pseudobassiana RGM 2184 has shown 80% maximum efficacy against the pest Lobesia botrana in the autumn and winter seasons. This suggests that the strain possesses an interesting battery of enzymes that are cold-adapted to penetrate the thick and hydrophobic cocoon of L. botrana. In this study, screening of the proteolytic, lipolytic, and chitinolytic activity of enzyme extracts secreted by the RGM 2184 strain was carried out in various culture media. The enzyme extracts with the highest activity were subjected to zymography and mass spectrometry. These analyses allowed the identification of two proteases, two lipases, and three chitinases. Comparative analysis indicated that the degree of similarity between these enzymes was substantially reduced when the highest degree of taxonomic relatedness between RGM 2184 and the entomopathogenic fungus strain was at the family level. These results suggest that there is a wide variety of exoenzymes in entomopathogenic fungi species belonging to the order Hypocreales. On the other hand, exoenzyme extract exposure of cocoons and pupae of L. botrana provoked damage at 10 °C. Additionally, an analysis of the amino acid composition of the RGM 2184 exoenzyme grouped them close to the cold-adapted protein cluster. These results support the use of this strain to control pests in autumn and winter. Additionally, these antecedents can form a scaffold for the future characterization of these exoenzymes along with the optimization of the strain’s biocontrol ability by overexpressing them.

Assessment of Fungal Lytic Enzymatic Extracts Produced Under Submerged Fermentation as Enhancers of Entomopathogens’ Biological Activity

“…Then, the proteases break down the peptide bonds of the sclerostin proteins from the exocuticle, revealing the chitin fibers. Finally, the exochitinases and endochitinases work together to break the chitin fibers [ 12 ]. However, the characterization of these enzymes has focused mainly on the fungi-cuticle insect interaction and selection of most virulent isolates [ 11 , 13 ], but the use of enzymatic extracts as enhancers of biological control agents has been less explored [ 6 ].…”

Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions

“…Toll-like receptors (TLRs) in Diaphorina citri were shown to be induced by endophytic B. bassiana [ 6 ]. Lobesia botrana pupae were shown to be susceptible to Beauveria pseudobassiana with those without a cocoon being more susceptible than those with a cocoon [ 7 ].…”