Screening and Functional Analysis of a Novel Salivary Effector DcE13 from the Asian Citrus Psyllid, <i>Diaphorina citri</i>

The lack of sequence similarity among insect effectors necessitates the independent identification of effectors in the Asian citrus psyllid <i>Diaphorina citri</i>, the primary vector of huanglongbing pathogens. In this study, nine candidate effectors were identified from the <i>D. citri</i> salivary gland transcriptome. Among them, <i>DcE13</i> exhibited the highest FPKM value and was delivered into plants during feeding. Transient expression in tobacco leaves showed that DcE13 is localized in the plasma membrane and around the nuclear envelope of plant cells. It inhibits <i>BAX</i>- and <i>INF1</i>-induced hypersensitive responses, suppresses callose deposition, and downregulates jasmonic acid marker genes <i>NtPDF1.2</i> and <i>NtFAD7</i>. Furthermore, <i>DcE13</i> knockdown decreased survival rates and fecundity of <i>D. citri</i>, as well as interrupted their phloem feeding, indicating its role as an effector that facilitates psyllid feeding. These results enrich our current understanding of <i>D. citri</i> feeding behavior while simultaneously offering a potential target gene for controlling this pest.