Carbon dioxide receptor genes and their expression profile in Diabrotica virgifera virgifera

Thais B. Rodrigues, Etsuko N. Moriyama, Hang Wang, Chitvan Khajuria, Blair D. Siegfried

Diabrotica virgifera virgifera, western corn rootworm, is one of the most devastating species in North America. D. v. virgifera neonates crawl through the soil to locate the roots on which they feed. Carbon dioxide (CO2) is one of the important volatile cues that attract D. v. virgifera larvae to roots. In this study, we identified three putative D. v. virgifera gustatory receptor genes (Dvv_Gr1, Dvv_Gr2, and Dvv_Gr3). Phylogenetic analyses confirmed their orthologous relationships with known insect CO2 receptor genes from Drosophila, mosquitoes, and Tribolium. The phylogenetic reconstruction of insect CO2 receptor proteins and the gene expression profiles were analyzed. Quantitative analysis of gene expression indicated that the patterns of expression of these three candidate genes vary among larval tissues (i.e., head, integument, fat body, and midgut) and different development stages (i.e., egg, three larval stages, adult male and female). The Dvv_Gr2 gene exhibited highest expression in heads and neonates, suggesting its importance in allowing neonate larvae to orient to its host plant. Similar expression patterns across tissues and developmental stages for Dvv_Gr1 and Dvv_Gr3 suggest a potentially different role. Findings from this study will allow further exploration of the functional role of specific CO2 receptor proteins in D. v. virgifera.