Novel sex pheromone desaturases in the genomes of corn borers generated through gene duplication and retroposon fusion

Abstract

The biosynthesis of female moth sex pheromone blends is controlled by a number of different enzymes, many of which are encoded by members of multigene families. One such multigene family, the acyl-CoA desaturases, is composed of certain genes that function as key players in moth sex pheromone biosynthesis. Although much is known regarding the function of some of these genes, very little is known regarding how novel genes have evolved within this family and how this might impact the establishment of new sex pheromone blends within a species. We have discovered that several cryptic ⌬11 and ⌬14 desaturase genes exist in the genomes of the European and Asian corn borers (Ostrinia nubilalis and Ostrinia furnacalis, respectively). Furthermore, an entirely novel class of desaturase gene has arisen in the Ostrinia lineage and is derived from duplication of the ⌬11 desaturase gene and subsequent fusion with a retroposon. Interestingly, the genes have been maintained over relatively long evolutionary time periods in corn borer genomes, and they have not been recognizably pseudogenized, suggesting that they maintain functional integrity. The existence of cryptic desaturase genes in moth genomes indicates that the evolution of moth sex pheromone desaturases in general is much more complex than previously recognized.

Repetitive genome elements in a European corn borer, Ostrinia nubilalis, bacterial artificial chromosome library were indicated by bacterial artificial chromosome end sequencing and development of sequence tag site markers: implications for lepidopteran genomic research

“…The OnB1 BESs 23N03-F and 23M11-F showed homology to an O. nubilalis reverse transcriptase (RT) and D11a-desaturase gene fusion locus (Xue et al 2007). The 23N03-F sequence (264 bp) has 94.6% homology to a 222 bp region of the first 21 amino acids of the RT and 157 bp of the upstream 5'-UTR.…”

“…The 04K12-F (ET217030) sequence had homology to introns of pbp and mannose 6-phosphate isomerase (mpi) alleles, as did the 23L07-F sequence (ET217030) to intron 2 of the Ostrinia furnacalis chitinase gene. Further investigations, presented below, indicated that the four sequences belonged to two types of repetitive genomic elements: LINEs related to the Ostrinia ezi-element (Xue et al 2007) and mobile MITE-like sequences.…”

On the origin of new genes in Drosophila

“…Such chimeric structures, if non-deleterious, are expected to immediately confer novel functions that the parental genes do not have and thus may also well explain the existence of functional duplicates (Patthy 1999). Besides the reported cases of chimeric new genes found within different species (Patthy 1999;Long et al 2003;Arguello et al 2006;Cordaux et al 2006;Xue et al 2007), their generality, the mutational mechanisms, and selective forces responsible for their formation remains an intriguing question to be addressed.…”

Evolution of moth sex pheromone composition by a single amino acid substitution in a fatty acid desaturase

“…Pheromone biosynthesis involves modifications of fatty acyl substrates, such as chain shortening and elongation, reduction, acetylation, oxidation, and desaturation (11). SP biosynthetic enzymes [i.e., FA reductases (8), FA chain-shortening enzymes (12, 13), and particularly FA desaturases (FADs) (7,9,(14)(15)(16)(17)] are the most commonly discovered traits underlying SP divergence in moths.Manduca sexta females attract males by releasing an SP containing in addition to mono-and diunsaturated aldehydes, which are typical structural themes in SPs of Bombycoidea moths (10), also uncommon conjugated triunsaturated aldehydes. The production of triunsaturated SPCs represents an easily traceable phenotype, thus making M. sexta a convenient yet unexploited model organism for unraveling the mechanisms of chemical communication evolution via novel SPC recruitment.…”

“…Pheromone biosynthesis involves modifications of fatty acyl substrates, such as chain shortening and elongation, reduction, acetylation, oxidation, and desaturation (11). SP biosynthetic enzymes [i.e., FA reductases (8), FA chain-shortening enzymes (12,13), and particularly FA desaturases (FADs) (7,9,(14)(15)(16)(17)] are the most commonly discovered traits underlying SP divergence in moths.…”