CREB-B acts as a key mediator of NPF/NO pathway involved in phase-related locomotor plasticity in locusts.

Gene expression changes in neural systems are essential for environment-induced behavioral plasticity in animals; however, neuronal signaling pathways mediating the effect of external stimuli on transcriptional changes are largely unknown. Recently, we have demonstrated that the neuropeptide F (NPF)/nitric oxide (NO) signaling pathway plays a regulatory role in phase-related locomotor plasticity in the migratory locust, Locusta migratoria. Here, we report that a conserved transcription factor, cAMP response element-binding protein B (CREB-B), is a key mediator involved in the signaling pathway from NPF2 to NOS in the migratory locust, triggering locomotor activity shift between solitarious and gregarious phases. We find that CREB-B directly activates brain NOS expression by interacting with NOS promoter region. The phosphorylation at serine 110 site of CREB-B dynamically changes in response to population density variation and is negatively controlled by NPF2. The involvement of CREB-B in NPF2-regulated locomotor plasticity is further validated by RNAi experiment and behavioral assay. Furthermore, we reveal that protein kinase A mediates the regulatory effects of NPF2 on CREB-B phosphorylation and NOS transcription. These findings highlight a precise signal cascade underlying environment-induced behavioral plasticity. Author summary The migratory locust, Locusta migratoria, is a worldwide agricultural pest that displays a remarkable density-dependent phase polyphenism, where being kept in a crowd triggers individuals to transit from the sedentary solitarious phase into the high-active gregarious phase. So, the migratory locust has been regarded as an excellent study model for environment-induced behavioral plasticity. Our previous finding shows that NPF2-regulated NOS transcription plays important roles in phase-related locomotor plasticity in the locust. Here, we further demonstrate that phosphorylated CREB-B directly activates NOS transcription in the pars intercerebralis, thus mediates phase-related locomotor plasticity. Further studies show that the levels of CREB-B phosphorylation is positively correlated with the crowding treatment and suppressed by NPF2. Among several candidate kinases, protein kinase A is demonstrated to transmit the inhibitory effects of NPF2 on CREB-B phosphorylation and NOS transcription. Our study provides deep insight into the precise regulatory mechanisms underlying environment-induced behavioral plasticity.