Metabolic analysis of BPH-induced changes
To investigate the metabolite changes associated with the functions ofOsAP79 , rice lines OE, knockout, and NIP were treated with BPH, and their metabolic compounds were identified using gas chromatography / mass spectrometry (GC-MS). A total of 216 compounds were identified (Table S5), and, according to principal component analysis (PCA), the expression patterns were notably different among the three genotypic lines (Figure S7 and S8). Of the 216 metabolites, 67 were mapped to the KEGG pathway and are indicated in an integrated metabolic map (Table S6). The mapped metabolites reflect the physiological state of BPH infection and play crucial roles in BPH resistance. They mainly participate in key metabolic pathways, such as the glycolysis, biosynthesis of alkaloids derived from the shikimate pathway, glucosinolate biosynthesis, and the citric acid cycle (Figure 6a and 6b).
Four key metabolic pathways were significantly enriched among the different genotypic lines, indicating that they are involved in the response to BPH feeding and may play a defensive role. Most of significantly different metabolites associated with cell wall were enriched in the shikimate pathway and citric acid cycle. Specifically, compared with that in knockout lines, the synthesis of glucosinolates such as valine, leucine, isoleucine, tyrosine, and phenylalanine, significantly increased in resistant lines after BPH infection. However, the content of D-glucose and fructose derived from glycolysis, citric acid and 2-Oxoglutaric acid derived from citrate cycle and shikimic acid decreased in OE and NIP lines when they were infected with BPH at 48 h and 72 h; nevertheless, no significant change was detected in the knockout lines (Figure 6a and 6b).