Abstract
BackgroundAedes aegypti is the most important global vector of dengue virus infection in humans. Availability of the draft genome sequence of this mosquito provides unique opportunities to study different aspects of its biology, including identification of genes and pathways relevant to the developmental processes associated with transition across individual life stages. However, detailed knowledge of gene expression patterns pertaining to developmental stages of A. aegypti is largely lacking.ResultsWe performed custom cDNA microarray analyses to examine the expression patterns among six developmental stages: early larvae, late larvae, early pupae, late pupae, and adult male and female mosquitoes. Results revealed 1,551 differentially expressed transcripts (DETs) showing significant differences in levels of expression between these life stages. The data suggests that most of the differential expression occurs in a stage specific manner in A. aegypti. Based on hierarchical clustering of expression levels, correlated expression patterns of DETs were also observed among developmental stages. Weighted gene correlation network analysis revealed modular patterns of expression among the DETs. We observed that hydrolase activity, membrane, integral to membrane, DNA binding, translation, ribosome, nucleoside-triphosphatase activity, structural constituent of ribosome, ribonucleoprotein complex and receptor activity were among the top ten ranked GO (Gene Ontology) terms associated with DETs. Significant associations of DETs were also observed with specific KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway modules. Finally, comparisons with the previously reported developmental transcriptome of the malaria vector, Anopheles gambiae, indicated that gene expression patterns during developmental processes reflect both species-specific as well as common components of the two mosquito species.ConclusionsOur study shows that genes involved in the developmental life cycle of A. aegypti are expressed in a highly stage-specific manner. This suggests that transcriptional events associated with transition through larval, pupal and adult stages are largely discrete.
Highlights
Aedes aegypti is the most important global vector of dengue virus infection in humans
Identification of differentially expressed transcripts related to development The DETs were determined at five developmental stages of A. aegypti: early larvae – late larvae (EL-LL), late larvae – early pupae (LL-EP), early pupae – late pupae (EP-LP), late pupae – adult male and female mix (LP-AdultMix) and adult male – adult (AM-AF)
These six common genes are related to chromatin assembly and disassembly, protein metabolic process as well as unknown functions. Four of these six genes displayed the same trend in expression in both species (Additional file 8). These results clearly suggest that gene expression patterns during developmental processes may have both common as well as distinct components in the two mosquito species, and that the expression patterns tend to diverge more in late stages compared to the earlier stages of development
Summary
Aedes aegypti is the most important global vector of dengue virus infection in humans. Mosquito (Culicidae) development, as characteristic of all holometabolous insects, proceeds through embryonic, larval, pupal, and adult stages that reflect considerable morphological and physiological differences. These stages exhibit distinct niche partitioning as larvae and pupae are aquatic while adults are free-flying and terrestrial. Larvae of all mosquito species progress through four instars that include periods of continuous growth interrupted by shedding of the old cuticle or ecdysis [3,4]. With the completion of the four instars of larval molting and sclerotization, metamorphosis, the transformation from larvae to pupae to adult stages, begins. The cascades of transcriptional events associated with insect ecdysis and metamorphosis are controlled by coordinated ecdysteroid and juvenile hormone (JH) activities [5,6,7]
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