Transcriptome exploration of the sex pheromone gland of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae)

Abstract

BackgroundMolecules involved in pheromone biosynthesis may represent alternative targets for insect population control. This may be particularly useful in managing the reproduction of Lutzomyia longipalpis, the main vector of the protozoan parasite Leishmania infantum in Latin America. Besides the chemical identity of the major components of the L. longipalpis sex pheromone, there is no information regarding the molecular biology behind its production. To understand this process, obtaining information on which genes are expressed in the pheromone gland is essential.MethodsIn this study we used a transcriptomic approach to explore the pheromone gland and adjacent abdominal tergites in order to obtain substantial general sequence information. We used a laboratory-reared L. longipalpis (one spot, 9-Methyl GermacreneB) population, captured in Lapinha Cave, state of Minas Gerais, Brazil for this analysis.ResultsFrom a total of 3,547 cDNA clones, 2,502 high quality sequences from the pheromone gland and adjacent tissues were obtained and assembled into 1,387 contigs. Through blast searches of public databases, a group of transcripts encoding proteins potentially involved in the production of terpenoid precursors were identified in the 4th abdominal tergite, the segment containing the pheromone gland. Among them, protein-coding transcripts for four enzymes of the mevalonate pathway such as 3-hydroxyl-3-methyl glutaryl CoA reductase, phosphomevalonate kinase, diphosphomevalonate descarboxylase, and isopentenyl pyrophosphate isomerase were identified. Moreover, transcripts coding for farnesyl diphosphate synthase and NADP+ dependent farnesol dehydrogenase were also found in the same tergite. Additionally, genes potentially involved in pheromone transportation were identified from the three abdominal tergites analyzed.ConclusionThis study constitutes the first transcriptomic analysis exploring the repertoire of genes expressed in the tissue containing the L. longipalpis pheromone gland as well as the flanking tissues. Using a comparative approach, a set of molecules potentially present in the mevalonate pathway emerge as interesting subjects for further study regarding their association to pheromone biosynthesis. The sequences presented here may be used as a reference set for future research on pheromone production or other characteristics of pheromone communication in this insect. Moreover, some matches for transcripts of unknown function may provide fertile ground of an in-depth study of pheromone-gland specific molecules.

The Lutzomyia longipalpis complex: a brief natural history of aggregation-sex pheromone communication

“…The costs of production are rarely demonstrated in insects (but see Johansson et al [94]), however these can be inferred indirectly in species where signal production commences after adult eclosion (as is the case for L. longipalpis [83]). Recent transcriptomics and proteomics studies have revealed much about the biosynthetic pathway for glandular secretions in Lutzomyia including the specific enzyme pathways involved in sesquiterpenoid biosynthesis [95, 96]. It was observed in L. longipalpis that if the diet is changed, e.g.…”

Novel family of terpene synthases evolved from trans -isoprenyl diphosphate synthases in a flea beetle

“…Sesquiterpenes are biosynthesized from three C 5 isopentenoid units supplied by the mevalonate pathway, which are then joined sequentially via the action of enzymes known as trans-isoprenyl diphosphate synthases (trans-IDS) to produce the linear C 15 intermediate (E,E)-farnesyl diphosphate (FPP). Trans-IDS enzymes have been identified and characterized in a number of insect species (4)(5)(6)(7)(8)(9)(10). The huge diversity of sesquiterpene carbon skeletons are formed from FPP in the next step by the catalysis of terpene synthases (TPSs).…”

“…Numerous TPSs have been identified in plants, fungi, and bacteria based on sequence similarity (11)(12)(13). However, no homologs of known terpene synthases have been reported from available insect genomic and transcriptomic sequences (3,7). A unique bifunctional enzyme producing the C 10 intermediate geranyl diphosphate (GPP) as well as the linear monoterpene myrcene in the bark beetle Ips pini represents the only insect terpene synthase known to date (14).…”

Insect pheromones: An overview of function, form, and discovery

“…Recently, using a combination of 622 genetics and biochemistry, the product of the cytochrome P450 623 gene Cyp4g1, was shown to catalyze the oxidative carbonylation 624 step in pheromone-producing oenocytes of Drosophila [180]. genome-editing tools will help in this regard [191][192][193][194][195]. showed that samples obtained from SPME exhibit the same quan-758 titative proportions as samples prepared by extraction [201].…”

“…First, in situ hybridization is useful for visualizing cellular 666 sites of gene expression in pheromone-producing tissues. Second, 667 next generation sequencing (NGS) technology is routinely applied 668to describe the transcriptome of pheromone glands[189][190][191].669 The combination of NGS with bioinformatic analysis of an increas-670 ing number of published genomes has allowed rapid identification 671 of putative enzyme candidates in many ''non-model'' species of 672 insects. Ultimately, however, the function and in vivo expression 673 of the candidate enzyme requires validation.…”