Nitrogen Limitation Improves Rice Resistance to Brown Planthopper by Boosting the ABA Signalling Pathway

ABSTRACT

Nitrogen level significantly impacts rice resistance to the brown planthopper (BPH, Nilaparvata lugens ). Yet, the mechanisms underlying nitrogen level‐mediated rice BPH resistance remain largely unclear. Here, we found that, relative to medium nitrogen (MN) and high nitrogen (HN) conditions, low nitrogen (LN) suppressed rice growth but enhanced plant resistance to BPH, as evidenced by reduced nymph biomass, decreased phloem ingestion and lower fecundity. Biochemical and transcriptome analyses revealed that compared to MN and HN plants, LN plants exhibited significantly higher basal and/or BPH‐induced levels of abscisic acid (ABA) and salicylic acid (SA), cell wall components (lignin, cellulose and hemicellulose), and certain flavonoids but lower levels of phenolamides. Moreover, the relative water content (RWC) and total amino acid concentrations were significantly lower in LN plants compared with those in MN and HN plants. Impairing the signalling pathway mediated by ABA but not SA in rice abolished the basal and/or BPH‐induced accumulation of defence compounds (cell wall components and certain flavonoids) in plants and plant resistance to BPH. The results demonstrate that the ABA signalling pathway, together with reduced RWC and total amino acid concentrations in plants caused by LN conditions, plays an important role in regulating the LN‐mediated rice resistance to BPH.