Silencing of Aquaporin Homologue Accumulates Uric Acid and Decreases the Lifespan of the Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae)

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama is devastating the citrus industry worldwide. It transmits ‘Candidatus Liberibacter asiaticus’, the pathogen of Huanglongbing in citrus. RNA interference is an excellent tool for functional genomics and for screening target genes for pest control. Herein, we silenced the aquaporin (AQP) gene (DcAQP) homologue in D. citri to study its functionality and whether it could be a good target for a control strategy. AQP is an integral membrane channel protein that aids in the rapid flux of water and other small solutes that move across the lipid membrane. In Hemiptera, it is well established that AQP plays important roles in adjusting to physiological challenges including (1) regulating osmotic stress between the gut lumen and hemolymph after imbibing large quantities of a low nitrogen, sugar-rich liquid diet; (2) avoiding or preventing dehydration and desiccation; and (3) surviving at elevated temperatures. The dsRNA-DcAQP was applied twice to nymphs of the 4th and 5th instars through a soaking technique. Silencing AQP caused a significant increase in nymph mortality. Emerged adults showed malformations and a shorter lifespan. Silencing DcAQP provoked alterations in some metabolites and increased the uric acid content in emerged adults. DcAQP could be a useful target to control D. citri.

Sub-optimal temperatures lead to altered expression of stress-related genes and increased ‘Candidatus Liberibacter solanacearum’ accumulation in potato psyllid

“…The predicted functions of the differentially expressed genes reported in this study are consistent with previous reports that have implicated abiotic stress genes, as well as aquaporin, which showed 2.8-fold increased expression in ‘Ca. L. solanacearum ’ -infected psyllids reared at 30°C, compared to 24°C ( 48 ). In addition, several cathepsin-like genes (5- to 18-fold) and a phenol oxidase gene (3-fold) showed greater expression in ‘Ca.…”

“…In whiteflies, it has been shown to be expressed in the filter chamber and hindgut of early instar nymphs and adults where it relieves osmotic stress by stabilizing water balance through recycling and excretion functions ( 45 ). Down-regulation of aquaporin homologs encoded by aphids ( 46 ), B. tabaci ( 45 , 47 ), and psyllids ( 48 ) resulted in disruption of normal osmoregulation functions, and for latter two insects, increased nymphal mortality and/or reduced lifespan of adults. In D. citri , knockdown evidence of differential changes in the metabolome and increased uric acid accumulation ( 48 ), which increases free radical-scavenging activity in hemolymph ( 49 ).…”

“…Down-regulation of aquaporin homologs encoded by aphids ( 46 ), B. tabaci ( 45 , 47 ), and psyllids ( 48 ) resulted in disruption of normal osmoregulation functions, and for latter two insects, increased nymphal mortality and/or reduced lifespan of adults. In D. citri , knockdown evidence of differential changes in the metabolome and increased uric acid accumulation ( 48 ), which increases free radical-scavenging activity in hemolymph ( 49 ).…”

RNA interference-mediated knockdown of genes involved in sugar transport and metabolism disrupts psyllid Bactericera cockerelli (Order: Hemiptera) gut physiology and results in high mortality

“…Another important process for regulating osmotic homeostasis involves the rapid transfer of water from the hemolymph and distal gut tissues to the sap ingestion site, facilitated by the transmembrane water channel, aquaporin ( 39 ). Aquaporins are abundant in the gut of the pea aphid Acyrthosiphon pisum (Harris) and whitefly Bemisia tabaci (Genn.)…”

“…and have been shown to regulate osmotic potential in cells where they are expressed ( 40 , 41 ). In ACP, reduced expression of aquaporins was found to lead to increased glucose concentration in whole-psyllid homogenates, and resulted in nymphal mortality ( 39 ).…”