Metabolomics reveals potential biomarkers of rice gall midge(Orseolia oryzae) interactions

【Objective】To detect differential levels of metabolites between rice gall midge(RGM) -resistant and -susceptible rice materials to provide a theoretical basis for analyzing rice-RGM interaction and assist in the development of green controls of RGM in rice.【Method】GXM-001-2(high resistance) and TN1(high susceptibility) were inoculated with RGM and liquid chromatography-mass spectrometry was employed to detect changes in metabolite levels after 48 h.【Result】330 metabolites were detected, of which 155 were known metabolites. TN1 displayed a much higher number of up-regulated metabolites after RGM infection than in GXM-001-2, where metabolites were largely down-regulated. The analysis of potential biochemical markers of rice infected by RGM showed that differentially regulated metabolites could be classified into four categories associated with resistance(n=16), susceptibility(n=16), infection(n=7) and host characteristics(n=3). Biochemical markers and fold change analysis showed that the resistance category included 1-aminocy-clopropanicarboxylic acid, 3-phosphoglyceric acid, eicosanoic acid, 6-methylvitamin D, glutamic acid, phyllol and tyrosine of which, the latter 4 were upregulated. Compounds associated with susceptibility included 2-hexketoic acid, 3-phenyllactic acid, 6-hydroxy hexanoic acid and other substances, of which 7 substances, including 6-hydroxy hexanoic acid, glucose and piceatannol, were downregulated. The characteristic compounds of infection included 4-aminobutyric acid, galactoic acid, propanedioic acid and adenine, uridine, propanedioic acid, and γ-aminobutyric acid showed similar up or down trends in GXM-001-2 and TN1. The host characteristic substances consisted of isoleucine, hexadecanoic acid and cycloleucine, with the former two substances at significantly higher levels in GXM-001-2 relative to TN1(P<0.05).【Conclusion】Under rice RGM condition, 16, 16, 7 and 3 metabolites associated with resistance, susceptibility, infection and host characteristics, respectively, were selected. Of these, fatty acids and their derivatives(hexadecanoic acid, eicosanoic acid, tetradecanoic acid and β-hydroxytetradecanoic acid), amino acids(glutamic acid, tyrosine, phenylalanine and g-aminobutyric acid), phenolic acids(ferulic acid), terpenoids(phyllol) and amines(acetanilide, benzylamine and lactamide) are the most important potential biomarkers of RGM infection, which could play important roles in plant insect defense responses.