Insight into maize gene expression profiles responses to symbiotic bacteria derived from Helicoverpa armigera and Ostrinia furnacalis.

The insects of Ostrinia furnacalis and Helicoverpa armigera are the two main pests that affect maize growth, which significantly decrease the yield. Plants induce various immune-related pathways to antagonize insect feeding during insect-plant interactions. Moreover, different insect elicitors or effectors participate in the interactions via releasing into plants. While there are many bacteria during insect regurgitation, their roles in insect-plant interaction are unknown. In this study, four bacterial strains were isolated from regurgitation fluid of O. furnacalis and H. armigera, and their cultures were inoculated on maize leaves for response analysis. All the four bacterial strains altered gene expression profiles in maize, and these altered expression profiles included phytohormones, secondary metabolic pathways, transcription factors, MAPK, and plant-pathogen interaction-related genes. A total of 210 genes, such as WRKY54, WRKY62, PIF5, argonaute 1, Xa21, NRR, ubiquitin-proteasome system genes, were co-changed in response to bacterial inoculation. These changes were similar with maize gene profile changes after insect feeding. Symbiotic insect bacteria participate in insect-plant interactions by changing maize gene expression profiles, which might be used to develop anti-pest microbial agents by activating plant defense system with identified microbes. In future, understanding the roles of symbiotic insect bacteria on plant-insect interaction might provide a promising and novel strategy for pest biocontrol using microbes.