Functional genetic characterization of salivary gland development in Aedes aegypti

Abstract

BackgroundDespite the devastating global impact of mosquito-borne illnesses on human health, very little is known about mosquito developmental biology. In this investigation, functional genetic analysis of embryonic salivary gland development was performed in Aedes aegypti, the dengue and yellow fever vector and an emerging model for vector mosquito development. Although embryonic salivary gland development has been well studied in Drosophila melanogaster, little is known about this process in mosquitoes or other arthropods.ResultsMosquitoes possess orthologs of many genes that regulate Drosophila melanogaster embryonic salivary gland development. The expression patterns of a large subset of these genes were assessed during Ae. aegypti development. These studies identified a set of molecular genetic markers for the developing mosquito salivary gland. Analysis of marker expression allowed for tracking of the progression of Ae. aegypti salivary gland development in embryos. In Drosophila, the salivary glands develop from placodes located in the ventral neuroectoderm. However, in Ae. aegypti, salivary marker genes are not expressed in placode-like patterns in the ventral neuroectoderm. Instead, marker gene expression is detected in salivary gland rudiments adjacent to the proventriculus. These observations highlighted the need for functional genetic characterization of mosquito salivary gland development. An siRNA- mediated knockdown strategy was therefore employed to investigate the role of one of the marker genes, cyclic-AMP response element binding protein A (Aae crebA), during Ae. aegypti salivary gland development. These experiments revealed that Aae crebA encodes a key transcriptional regulator of the secretory pathway in the developing Ae. aegypti salivary gland.ConclusionsThe results of this investigation indicated that the initiation of salivary gland development in Ae. aegypti significantly differs from that of D. melanogaster. Despite these differences, some elements of salivary gland development, including the ability of CrebA to regulate secretory gene expression, are conserved between the two species. These studies underscore the need for further analysis of mosquito developmental genetics and may foster comparative studies of salivary gland development in additional insect species.

De novo transcriptome analysis shows differential expression of genes in salivary glands of edible bird’s nest producing swiftlets

“…Despite their compact size they are able to produce the required volume of saliva via the interconnected network of secretory acini and ducts through a complex, epithelial-branching, morphogenesis process. Research on fly ( Drosophila melanogaster ) salivary glands identified both CREBA and PAPS synthetase genes as early and late markers of salivary gland development, respectively [45, 46]. A previous study on fly salivary glands showed that CREBA is a Drosophila homolog of the CREB3 family of transcription factors which includes five different proteins in mammals, namely CREB3 , CREB3L1 , CREB3L2 , CREB3L3 , and CREB3L4 .…”

“…3). Studies on the salivary glands D. melanogaster and Aedes aegypti revealed that CREB3L2 and the expression of several important cell type-specific secreted component genes (SPCGs) are involved in salivary secretion and control of the saliva flow rate [45, 46]. SPCGs are genes that encode for protein machinery that targets and/or translocates proteins in the endoplasmic reticulum, regulates vesicle transport between the endoplasmic reticulum and Golgi, and cleaves the N-terminal signal sequence [47].…”

Developmental neurogenetics of sexual dimorphism in Aedes aegypti

“…Microinjected siRNA (Clemons et al, 2010b) can be used to target A. aegypti developmental genes (Clemons et al, 2011; Haugen et al, 2011; Nguyen et al, 2013; Sarro et al, 2013; Tomchaney et al, 2014). siRNA can also be delivered to A. aegypti larvae via chitosan nanoparticles (Mysore et al, 2013, 2014a,b) that are mixed with larval food and orally ingested by larvae, and which may promote the stability and cellular uptake of interfering RNA (Zhang et al, 2010).…”

Requirement for commissureless2 function during dipteran insect nerve cord development

“…To explore this, we opted to assess comm2 gene function in A. aegypti because it has retained a single comm family ortholog (Fig. 1), and also due to the fact that we recently optimized embryonic knockdown strategies in this species (Clemons et al, 2010a(Clemons et al, , 2011Haugen et al, 2011;Nguyen et al, 2013), which is to our knowledge the only mosquito species in which embryonic RNAi knockdown studies have been published to date. First, Aae comm2 expression was assessed in detail during A. aegypti embryonic CNS development.…”

“…Knockdown of Aae comm2 was performed through embryonic microinjection of siRNAs corresponding to this gene as previously described in a protocol (Clemons et al, 2010a) which has been successfully used in three recent embryonic knockdown investigations (Clemons et al, 2011;Haugen et al, 2011;Nguyen et al, 2013). The following siRNAs corresponding to Ae.…”