Combined Physio-Biochemical and Transcriptome Analyses Illuminate the Resistance Response of Rice Priming with Decoyinine against Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a notorious pest in rice production. The microbial secondary metabolite, decoyinine (DCY), is produced by Streptomyces hygroscopicus. Recent studies found that seed priming with DCY could enhance rice resistance to BPH and Laodelphax striatellus; however, the mechanism of enhancing insect resistance in rice remains unclear. Here, an integrated physio-biochemical and transcriptome analysis was performed on rice priming with DCY after BPH infestation. Defense-related enzymes activities such as catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), glutathione S transferase (GST), and polyphenol oxidase (PPO), concentrations of hydrogen peroxide (H2O2), callose, and free amino acids in rice priming with DCY were significantly increased than in control plants after BPH infestation. Concentrations of soluble sugars, sucrose, and glucose were higher in rice treated with DCY than in the control after BPH infestation; however, the concentration of malondialdehyde (MDA) was significantly decreased in rice treated with DCY after BPH infestation. In the transcriptome analysis, GO functional annotation and KEGG pathway analysis were enriched in defense response, transcription factors, secondary metabolites, reactive oxygen species, and cell wall organization and these data also support physio-biochemical results. The qRT-PCR results further verified the differential expressed genes related to DCY-treated rice responding to BPH. Meanwhile, it indicated that DCY might enhance the resistance of rice to BPH by regulating the rice WRKY transcription factor genes. Our results provide a basis for further exploring the molecular mechanism of the defense response of rice priming with DCY against BPH infestation and could provide valuable resources to control insect pests.