The SNMP/CD36 gene family in Diptera, Hymenoptera and Coleoptera: Drosophila melanogaster, D. pseudoobscura, Anopheles gambiae, Aedes aegypti, Apis mellifera, and Tribolium castaneum

Sensory neuron membrane proteins (SNMPs) are membrane bound proteins initially identified in olfactory receptor neurons of Lepidoptera and are thought to play a role in odor detection; SNMPs belong to a larger gene family characterized by the human protein CD36. We have identified 12-14 candidate SNMP/CD36 homologs from each of the genomes of Drosophila melanogaster, D. pseudoobscura, Anopheles gambiae and Aedes aegypti (Diptera), eight candidate homologs from Apis mellifera (Hymenoptera), and 15 from Tribolium castaneum (Coleoptera). Analysis (sequence similarity and intron locations) suggests that the insect SNMP/CD36 genes fall into three major groups. Group 1 includes the previously characterized D. melanogaster emp (epithelial membrane protein). Group 2 includes the previously characterized D. melanogaster croquemort, ninaD, santa maria, and peste. Group 3 genes include the SNMPs, which fall into two subgroups referred to as SNMP1 and SNMP2. D. melanogaster SNMP1 (CG7000) shares both significant sequence similarity and five of its six intron insertion sites with the lepidopteran Bombyx mori SNMP1. The topological conservation of this gene family within the three major holometabolous lineages indicates that it predates the coleopteran and hymenoptera/dipera/lepidoptera split 300+ million years ago. The current state of knowledge of the characterized insect members of this gene family is discussed.