Exogenous Calcium-Mediated Reinforcement of Cell Wall Represents a Pivotal Mechanism in Rice’s Primed Defense Response Against Brown Planthopper Reproduction

The plant cell wall serves as the primary structural barrier against herbivorous insect damage. Calcium ions (Ca²⁺) play a crucial role as a second messenger in plants. Exogenous calcium application has been demonstrated to enhance plant resistance to both biotic and abiotic stresses, thereby promoting sustainable crop production. This study investigates the mechanisms by which exogenous calcium induces resistance in rice. Our results show that calcium chloride (CaCl₂) promotes the biosynthesis of cellulose, pectin, and callose within the rice cell wall. It also up-regulates the expression of genes associated with cell wall component synthesis (OsCESA8, OsPME15, and OsGRP0.9) and callose synthesis (OsGSL1, OsGSL10, and OsGSL12). These biochemical modifications strengthen the cell wall structure, resulting in reduced nutrient availability for the female brown planthopper (BPH), Nilaparvata lugens. Consequently, the growth and development of BPH are hindered, ovarian development is delayed, and the expression levels of NlVg and NlVgR genes are reduced. These physiological alterations lead to a shortened oviposition period, reduced longevity, and decreased fecundity in female BPH. Our findings indicate that CaCl₂ strengthens the cell wall structure and promotes callose deposition as a critical defense mechanism in rice. This research provides a foundation for further exploration of the molecular mechanisms and cellular processes underlying exogenous calcium-induced resistance in rice and offers a promising strategy for environmentally friendly BPH management.