Differential expression of SNMPs and their underlying transcriptional regulation in chemosensory pathways of Drosophila.

摘要

Insects possess complex and diverse chemosensory pathways which have specific phenotypes determined by the regulated expression of specific combinations of genes. While many of these genes (e.g. ORs and GRs) have very narrow expression patterns, associating with only a limited number of chemosensory sensilla, SNMPs show a very broad expression pattern. In Drosophila, SNMP1 and SNMP2 associate with the majority of olfactory and gustatory sensilla, but express in different cell types. In olfactory sensilla, SNMP1 and SNMP2 associate with trichoid or coeloconic neurons respectively, and both additionally express in a variety of sensilla support cells; in gustatory sensilla, SNMP2 expresses in neurons while SNMP2 expresses in support cells. We have characterized the SNMP1 and SNMP2 promoters to (1) identify minimal promoter units, (2) to identify regulatory mechanisms directing expression to specific cells or tissues (e.g. wings, legs, neurons, support cells) (3) and to determine if SNMPs and ORs/GRs have independently acquired common regulatory elements.;For both SNMP1 and SNMP2 genes, we identified relatively short regions (~350bp) directly upstream of the transcriptional start sites that directed the majority of expression observed for longer promoters (>3kb). Pertinent to specific tissues, we demonstrated the presence of negative and positive regulatory elements both upstream and downstream of these regions. And we demonstrated the existence of common regulatory elements shared by SNMPs and specific ORs. In general, expression in different tissues or cell types appeared to require specific combinations of regulatory elements. The identification of common cis - regulatory elements in evolutionarily unrelated SNMP and OR/GR genes suggests that chemosensory gene expression is evolutionarily malleable.