Figure 6.

Pathogen-encoded miRNAs regulating insect immunity. Pathogen-derived miRNAs often translocate via extracellular vesicles (EVs) to regulate insect host immunity. Upon fungal invasion, translocated fungal miRNAs downregulate the insect Toll signaling pathway by repressing the expression of critical genes, such as Spz4, or inhibiting the peroxisome pathway, repressing the expression of the PXE16 gene. At the late stage of infection, fungi act by decreasing the expression of their miRNAs to escape the melanization process (yellow). Upon viral attacks, translocated virus-derived miRNAs act individually or synergistically to negatively regulate the expression of insect key genes (Ran, Apaf-1, etc.) by targeting their 3′UTR regions. The latter downregulation reduces host miRNAs’ production, leading to viral replication and proliferation (purple). However, the figure does not show the bacterial-derived miRNAs due to missing data on their role in insect–bacterium interaction.