The spatiotemporal immune response patterns of Gryllus bimaculatus to infection by the bioinsecticide Metarhizium anisopliae.

In the contemporary context of agricultural pest management, bioinsecticides have emerged as a sustainable alternative to conventional chemical insecticides, representing a growing trend of significance. Gryllus bimaculatus, a species of Orthoptera that serves as a valuable model for studying immune responses to fungal bioinsecticide infection, thereby contributing to a deeper understanding of insect immune mechanisms within this order. In this study, the expression patterns of immune responses in G. bimaculatus were analysed at three critical time points following infection with the bioinsecticide Metarhizium anisopliae: early (12 h), middle (36 h), and late (72 h). A total of 89 differentially expressed immune-related genes were identified across two major immune tissues: hemocytes and fat body. The results of the study demonstrated that during the initial phase of infection, the immune response was predominantly orchestrated by hemocytes, marked by heightened expression of immunomodulatory factors, activation of the Toll signalling pathway, and up-regulation of effector molecules such as nitric oxide synthase. In the subsequent stage, hemocytes and the fat body respond in a synergistic manner to the invasion of pathogens, resulting in significant enrichment of immune-related functions and elevated expression of the majority of immune-related genes. This observation signifies that this stage corresponds to the period of maximal immune activation. In the late stage, although the overall immune response declined, the host continued to mount a defence against fungal infection. This study provides novel insights into the immune response mechanisms of G. bimaculatus. It identifies candidate targets involved in host-pathogen interactions and offers a theoretical foundation for the development and optimisation of novel fungal bioinsecticides.