A small expressed sequence tag (EST) project generating 506 ESTs from 375 cDNAs was undertaken on the antennae of male Manduca sexta moths in an effort to discover olfactory receptor proteins. We encountered several clones that encode apparent transmembrane proteins; however, none is a clear candidate for an olfactory receptor. Instead we found a greater diversity of odourant binding proteins (OBPs) than previously known in moth antennae, raising the number known for M. sexta from three to seven. Together with evidence of seventeen members of the family from the Drosophila melanogaster genome project, our results suggest that insects may have many tens of OBPs expressed in subsets of the chemosensory sensilla on their antennae. These results support a model for insect olfaction in which OBPs selectively transport and present odourants to transmembrane olfactory receptors. We also found five members of a family of shorter proteins, named sensory appendage proteins (SAPs), that might also be involved in odourant transport. This small EST project also revealed several candidate odourant degrading enzymes including three P450 cytochromes, a glutathione S-transferase and a uridine diphosphate (UDP) glucosyltransferase. Several first insect homologues of proteins known from vertebrates, the nematode Caenorhabditis elegans, yeast and bacteria were encountered, and most have now also been detected by the large D. melanogaster EST project. Only thriteen entirely novel proteins were encountered, some of which are likely to be cuticle proteins.

Pigmentation has emerged as a premier model for understanding the genetic basis of phenotypic evolution, and a growing catalog of color loci is starting to reveal biases in the mutations, genes, and genetic architectures underlying color variation in the wild. However, existing studies have sampled a limited subset of taxa, color traits, and developmental stages. To expand our sample of color loci, we performed quantitative trait locus (QTL) mapping analyses on two types of larval pigmentation traits that vary among populations of the redheaded pine sawfly (Neodiprion lecontei): carotenoid-based yellow body color and melanin-based spotting pattern. For both traits, our QTL models explained a substantial proportion of phenotypic variation and suggested a genetic architecture that is neither monogenic nor highly polygenic. Additionally, we used our linkage map to anchor the current N. lecontei genome assembly. With these data, we identified promising candidate genes underlying: (1) a loss of yellow pigmentation in Mid-Atlantic/northeastern populations (Cameo2 and apoLTP-II/I), and (2) a pronounced reduction in black spotting in Great-Lakes populations (yellow, TH, Dat). Several of these genes also contribute to color variation in other wild and domesticated taxa. Overall, our findings are consistent with the hypothesis that predictable genes of large-effect contribute to color evolution in nature.

Pigmentation has emerged as a premier model for understanding the genetic basis of phenotypic evolution, and a growing catalog of color loci is starting to reveal biases in the mutations, genes, and genetic architectures underlying color variation in the wild. However, existing studies have sampled a limited subset of taxa, color traits, and developmental stages. To expand the existing sample of color loci, we performed QTL mapping analyses on two types of larval pigmentation traits that vary among populations of the redheaded pine sawfly (): carotenoid-based yellow body color and melanin-based spotting pattern. For both traits, our QTL models explained a substantial proportion of phenotypic variation and suggested a genetic architecture that is neither monogenic nor highly polygenic. Additionally, we used our linkage map to anchor the current genome assembly. With these data, we identified promising candidate genes underlying (1) a loss of yellow pigmentation in populations in the mid-Atlantic/northeastern United States [C locus-associated membrane protein homologous to a mammalian HDL receptor-2 gene () and lipid transfer particle apolipoproteins II and I gene ()], and (2) a pronounced reduction in black spotting in Great Lakes populations [members of the gene family, tyrosine hydroxylase gene (), and dopamine -acetyltransferase gene ()]. Several of these genes also contribute to color variation in other wild and domesticated taxa. Overall, our findings are consistent with the hypothesis that predictable genes of large effect contribute to color evolution in nature.

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