Abstract
Plant resistance to herbivores is a key component in integrated pest management. In most cases, silicon (Si) amendment to plants enhances resistance to herbivorous insects. The increase of plant physical barrier and altered insect behaviors are proposed as mechanisms for the enhanced resistance in Si-amended plants, but our understanding of the induced mechanisms involved in Si-enhanced plant resistance to phloem-feeding insects remains unclear. Here, we show that Si amendment to rice (Oryza sativa) plants impacts multiple plant defense responses induced by a phloem-feeder, the brown planthopper (Nilaparvata lugens, BPH). Si amendment improved silicification of leaf sheaths that BPH feed on. Si addition suppressed the increase of malondialdehyde concentration while encouraged increase of H2O2 concentration in plants attacked by BPH. Higher activities of catalase and superoxide dismutase were recorded in Si-amended than in non-amended BPH-infested plants. BPH infestation activated synthases for secondary metabolites, polyphenol oxidase and pheny-lalanine ammonia-lyase, and β-1,3-glucanase, but the activation was greater in Si-amended than in non-amended plants. Taken together, our findings demonstrate that Si amendment interacts with BPH infestation in the induction of plant defense responses and consequently, to confer enhanced rice plant resistance.
Highlights
The brown planthopper (Nilaparvata lugens Stål; BPH) is a destructive and migratory insect pest that feeds on the leaf sheath of rice (Oryza sativa L.)
Si is not listed as an essential element for higher plants, its role in mediating resistance to a wide range of abiotic and biotic stresses is beyond doubt[6,7,8,9, 18, 24]
One of the mechanisms of Si-mediated plant resistance to herbivores is that Si is accumulated in epidemic cells, which forms a physical barrier against herbivory[9, 10, 12]
Summary
The brown planthopper (Nilaparvata lugens Stål; BPH) is a destructive and migratory insect pest that feeds on the leaf sheath of rice (Oryza sativa L.). It damages plants by ingesting phloem sap via its piercing mouthparts, which generally results in a symptom of hopperburn in susceptible plants when pest populations are large. Si-mediated resistance may be realized through priming chemical defense in plants[5, 11, 12] and augmented release of herbivore-induced plant volatiles that attract natural enemies of the attacking pests[13]. Herbivorous feeding usually induces a battery of chemical defense responses in plants, on which Si is reported to play a role. The physiological mechanism underlying Si-mediated feeding impairment and decreased population growth remains unknown
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