A retinal-binding protein mediates olfactory attraction in the migratory locusts.

Cellular retinaldehyde-binding protein (CRALBP) is abundantly expressed in retina and its mutations are associated with visual impairments. The functions of CRALBP are less known in extra retinal tissues. Herein, we study the function of CRALBP in modulating olfactory behaviors in gregarious and solitary locusts. The expressions of cralbp mRNA and protein were enriched in locust brains and antennae. RNAi knockdown of cralbp in gregarious locusts decreased their attractive response to gregarious volatiles. RNA-seq and quantitative PCR confirmed that cralbp mRNA and protein expression levels were upregulated and downregulated after octopamine receptor α1 (OctαR1) activation and inhibition, respectively. Gene network analysis revealed that cralbp is the core hub gene in the interactive network among differentially expressed transcripts (DETs) resulting from activating and inhibiting OctαR1. Moreover, cralbp RNAi knockdown inhibited the induction of olfactory attraction by octopamine (OA)-OctαR1 signaling. CRALBP helped to transmit OA signals to mediate olfactory attraction response to guaiacol and veratrole, which are two odorant components in gregarious volatiles. This study suggested that CRALBP may act as a novel effector protein in OctαR1 signaling to mediate olfactory attraction. This study indicated that CRALBP modulates olfactory attraction in extra retina tissues and retinaldehyde metabolism may be crucial for olfactory attraction modulation.