Identification and expression analysis of candidate chemosensory receptors based on the antennal transcriptome of Lissorhoptrus oryzophilus.

The rice water weevil Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae) is a worldwide agricultural pest that causes serious damage to rice. The olfactory and gustatory behaviors of L. oryzophilus in locating host plants and oviposition sites mostly rely on the detection of chemical stimuli in the environment. To reveal such olfactory and gustatory systems, we performed a systematic analysis of major chemosensory receptor genes. The antennal transcriptome of adult female L. oryzophilus was sequenced and assembled using the Illumina sequencing platform. A total of 60 candidate chemosensory receptor genes were ultimately identified, including 41 putative odorant receptors (ORs), 10 ionotropic receptors (IRs) and 9 gustatory receptors (GRs). Relatedness with other species was predicted based on phylogenetic results, and specific chemosensory receptor genes were analyzed, including Orco, carbon dioxide receptors and sugar receptors. Furthermore, qRT-PCR analyses of chemosensory receptor genes showed 59 genes to be antenna-biased genes, whereas only 1 gene was predominantly expressed in non-olfactory tissues. Our research provides insight for understanding olfactory and gustatory systems in the antennae of L. oryzophilus and facilitating the discovery of novel strategies for controlling this pest.