Biochemical and molecular profile alterations in Locusta migratoria migratorioides (Orthoptera: Acrididae) induced by the entomopathogenic fungi

Abstract

Locusta migratoria (Linnaeus, 1758) (Orthoptera: Acrididae) poses a significant agroecological threat due to its density-dependent phase polymorphism, exhibiting distinct phenotypic variations (e.g., in morphology, physiology, and behavior) in response to changes in population density, culminating in migratory swarms that inflict substantial agricultural losses across Afro-Eurasia. This study evaluated the impact of two entomopathogenic fungi, Beauveria bassiana (AUMC9899) and Metarhizium anisopliae (AUCM5130), on the biochemical and molecular profiles of L. migratoria under semi-field conditions. Both fungi demonstrated considerable insecticidal efficacy. B. bassiana induced nymphal mortality rates of 48.30 % at its LC₅₀ and 87.33 % at its LC₉₀ after seven days, while M. anisopliae similarly resulted in 47 % and 85 % nymphal mortality at these respective concentrations. At their respective LC₅₀ concentrations (1.7 × 10⁵ and 1.7 × 10⁶ conidia/mL), both B. bassiana and M. anisopliae caused significant reductions in essential nutrient reserves by day 7. Total protein was reduced by 51.10 % (B. bassiana) and 53.39 % (M. anisopliae). Total carbohydrates decreased by 12.98 % (B. bassiana) and 18.26 % (M. anisopliae), while total lipids were reduced by 24.58 % (B. bassiana) and 38.14 % (M. anisopliae). These changes were accompanied by altered key enzyme activities in whole-body homogenates, including increased protease and chitinase and decreased trehalase. Furthermore, SDS-PAGE analysis of hemolymph revealed shared and distinct changes in protein profiles, indicating complex host-pathogen interactions. Both treatments led to the disappearance of higher molecular weight bands (∼232 kDa). B. bassiana developed a distinct band at ∼210 kDa on day 5, which was not observed in the control. While M. anisopliae exhibited a band at ∼212 kDa at the same day 5 time point. Furthermore, M. anisopliae exhibited bands in the ∼47–65 kDa range on days 3 and 5 that were no longer detectable by day 7, similar to B. bassiana, which also showed a reduction in this range by day 7, demonstrating pathogen-specific responses. These findings provide a deeper understanding of the insecticidal mechanisms of these entomopathogenic fungi and highlight their potential for biological control strategies against L. migratoria.