A phospholipase A2 gene is linked to Jack bean urease toxicity in the Chagas' disease vector Rhodnius prolixus

Ureases are multifunctional enzymes that display biological activities independent of their enzymatic function, including exocytosis induction and insecticidal effects. The hemipteran Rhodnius prolixus is one of the known susceptible models for this toxicity. It has been shown that Jack bean urease (JBU) has deleterious effects on R. prolixus, and these effects are modulated by eicosanoids, which are synthesized in a cascade involving phospholipase A2 (PLA2) enzymes.

R. prolixus genome was screened for putative PLA2s and matching transcripts were cloned. Predicted amino acid sequences were analyzed and transcript distribution among tissues was determined by qPCR. RNAi techniques were used and subsequent JBU toxicity assays were performed.

Two PLA2 genes were identified, Rhopr-PLA2III and Rhopr-PLA2XII. The transcripts are widely distributed in the tissues but at different levels. The analyses fit the putative proteins into groups III and XII of secretory PLA2s. After 70% of Rhopr-PLA2XII expression was knocked down, JBU's toxicity was decreased by more than 50% on 5th instars R. prolixus.

Rhopr-PLA2XII gene is linked to JBU's toxic effect in R. prolixus and our findings support previous studies demonstrating that eicosanoids modulate this toxicity.

Besides identifying and characterizing two PLA2 genes in the major Chagas' disease vector R. prolixus, we have shown that the potent toxicity of JBU is linked to one of these genes. Our results contribute to the general comprehension of urease's mechanisms of action in insects, and, potentially, to studies on the control of the Chagas' disease parasite transmission.