Effector enrichment by Candidatus Liberibacter promotes Diaphorina citri feeding via Jasmonic acid pathway suppression

Abstract BACKGROUND Citrus huanglongbing (HLB) is a devastating disease caused by Candidatus Liberibacter asiaticus ( C Las) that affects the citrus industry. In nature, C Las relies primarily on Diaphorina citri Kuwayama as its vector for dissemination. After D. citri ingests C Las‐infected citrus, the pathogen infiltrates the insect's body, where it thrives, reproduces, and exerts regulatory control over the growth and metabolism of D. citri . Previous studies have shown that C Las alters the composition of proteins in the saliva of D. citri , but the functions of these proteins remain largely unknown. RESULTS In this study, we detected two proteins (DcitSGP1 and DcitSGP3) with high expression levels in C Las‐infected D. citri . Quantitative PCR and Western blotting analysis showed that the two proteins were highly expressed in the salivary glands and delivered into the host plant during feeding. Silencing the two genes significantly decreased the survival rate for D. citri , reduced phloem nutrition sucking and promoted jasmonic acid (JA) defenses in citrus. By contrast, after overexpressing the two genes in citrus, the expression levels of JA pathway‐associated genes decreased. CONCLUSION Our results suggest that C Las can indirectly suppress the defenses of citrus and support feeding by D. citri via increasing the levels of effectors in the insect's saliva. This discovery facilitates further research into the interaction between insect vectors and pathogens. © 2024 Society of Chemical Industry.