Abstract
IntroductionThe brown planthopper (BPH, Nilaparvata lugens Stål, Hemiptera: Delphacidae) is one of the most devastating insect pests of the crucially important cereal crop, rice (Oryza sativa L.). Currently, multiple BPH-resistant rice varieties have been cultivated and generalized to control BPH. However, the defence metabolic responses and their modes of action against BPH in different rice cultivars remain uncharacterized.ObjectiveWe used a non-biased metabolomics approach to explore the differences in metabolite profiles in response to BPH infestation in the susceptible TN1 rice cultivar and two resistant cultivars (IR36 and IR56).MethodsThe metabolomic detection based on gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry (LC–MS) was performed to investigate the content changes of identified metabolites in TN1, IR36 and IR56 rice varieties at various time points (0 h, 24 h, 48 h and 96 h) post BPH feeding. The differentially expressed metabolites were screened and the corresponding metabolic pathways were further enriched.ResultsThe results showed that compared to that in TN1, the content changes of most primary metabolites were more stable, but the concentration alterations of some defence-related metabolites were more acute and persistent in IR36 and IR56. Furthermore, the differentially expressed pathways analysis revealed that cyanoamino acids and lipids metabolism was persistently induced in IR36, but changes in thiamine, taurine and hypotaurine metabolism were more significant in IR56 during BPH infestation. Besides, the contents of quercetin and spermidine which were harmful to BPH fitness, were significantly elevated by BPH in TN1 and IR36, and the quercetin level was significantly decreased during BPH feeding in IR56.ConclusionThe results of the differences in metabolite profiles in response to BPH infestation in different rice cultivars were useful to clarify the metabolic mechanism of rice plants during BPH infestation and to provide new resources to control this insect pest.
Highlights
The brown planthopper (BPH, Nilaparvata lugens Stål, Hemiptera: Delphacidae) is one of the most devastating insect pests of the crucially important cereal crop, rice (Oryza sativa L.)
The results showed that the metabolic profiles of different rice samples could be clearly separated into three main groups in terms of rice cultivars, and subgroups were further defined based on BPH treatments within each rice variety (Fig. 1)
The results showed that at most of the BPH feeding stages, the expression levels of quercetin synthesis-related genes, including the chalcone synthase gene (CHS), phenylalanine ammonialyase gene (PAL) and flavonol synthase gene (FLS), were significantly elevated by BPH feeding in TN1 and IR36 rice varieties (p < 0.05, ANOVA, Fig. 2), but 24 h and 48 h feeding significantly lowered the expression of CHS in IR56 rice plants (p < 0.05, ANOVA, Fig. 2)
Summary
The brown planthopper (BPH, Nilaparvata lugens Stål, Hemiptera: Delphacidae) is one of the most devastating insect pests of the crucially important cereal crop, rice (Oryza sativa L.). Conclusion The results of the differences in metabolite profiles in response to BPH infestation in different rice cultivars were useful to clarify the metabolic mechanism of rice plants during BPH infestation and to provide new resources to control this insect pest. Plants have developed multiple resistance strategies to defend themselves against attack from herbivorous insects, which could be generalized into constitutive and induced defences (Howe and Jander 2008; Schuman and Baldwin 2016). As the end product of gene expression, plant metabolites, including primary metabolites and secondary metabolites, could participate in pest resistance by regulating the host’s basic biological activities or acting as insect toxins (Schwachtje and Baldwin 2008; Kessler 2015; Zhou et al 2015). In combination with other omics sciences, such as transcriptomics or proteomics, metabolomics is becoming a key tool in the comprehensive understanding of the gene expression and metabolic regulation of plants to herbivory (Sumner et al 2003; Schauer and Fernie 2006) and discovering the potential bioactive compounds that participate in plant–insect interactions (Jansen et al 2009)
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