Syntaxin-1A Silencing by RNAi Disrupts Growth and Reproduction in the Asian Citrus Psyllid, Diaphorina citri

<i>Diaphorina citri</i> is the primary global vector of "<i>Candidatus</i> Liberibacter asiaticus", the bacterium responsible for Huanglongbing. Syntaxin-1A (<i>Syx1A</i>), a member of the Qa-SNARE family, is essential for vesicle fusion and signal transduction, though its function in hemipteran insects remains poorly understood. This study presents the first comprehensive analysis of <i>Syx1A</i> expression in <i>D. citri</i>. Transcripts were detected across all life stages, with peak expression in the salivary glands. RNAi silencing of <i>Syx1A</i> reduced mRNA levels by 39.0% in nymphs and 58.0% in adults, resulting in 58.3% nmortality in nymphs within 5 days and 73.3% in adults within seven days, along with significant weight loss. Treated females showed marked declines in fecundity, ovarian degeneration, and deficient yolk deposition. RT-qPCR confirmed significant downregulation of <i>Vg1</i>, <i>VgA</i>, and <i>VgR</i>. These findings establish <i>Syx1A</i> as a regulator of growth and reproduction in citrus psyllids via modulation of yolk synthesis. RNAi targeting of <i>Syx1A</i> represents a promising strategy for ecologically sound pest control and may contribute to efforts in halting the transmission of the Huanglongbing pathogen <i>C</i>Las.