Lipophorin receptor knockdown reduces hatchability of kissing bug Rhodnius prolixus eggs

Abstract

Lipophorin is the primary lipoprotein present in the hemolymph of insects, responsible for the lipids' transport between organs. It interacts with specific sites on cell membranes in an essential process for transferring lipids. The lipophorin receptor is the protein responsible for the interaction between lipophorin and cell membranes. In the kissing bug Rhodnius prolixus, much information on the interaction of lipophorin with organs is available. However, molecular data on the lipophorin receptor and its functions is still needed. Here, we explored lipophorin receptor gene expression and functions using a functional genomics approach. The R. prolixus genome encodes seven genes from the low-density lipoprotein receptor family, including a single ortholog of the lipophorin receptor. All organs analyzed (anterior and posterior midguts, fat body, ovaries, and flight muscle) expressed this gene. In the fat body, blood-feeding strongly reduced lipophorin receptor gene expression. Lipophorin receptor knockdown by RNA interference delayed egg laying and reduced the triacylglycerol in laid eggs without altering lipid stores in the fat body or lipid levels in the hemolymph. In the ovaries, lipophorin receptor knockdown reduces the expression of acetyl-CoA carboxylase and a fatty acid synthase while altered the gene expression profile in the fat body, causing an increase in the expression of carnitine palmitoyltransferase 1 and a reduction in Brummer lipase and vitellogenin 2. RNA interference treatment reduced the hatching of the eggs, causing the collapse and darkening of the laid eggs, in addition to the hatching of deformed first-stage nymphs. Furthermore, the structure of the chorion showed distortions in patterns and cracks and reduced hydrocarbon levels. These results show that the lipophorin receptor alone is not essential for lipid physiology in R. prolixus. However, this protein plays a fundamental role in the viability of eggs and, consequently, in insect reproduction.