Changes in transcript abundance for cuticular proteins and other genes three hours after a blood meal in Anopheles gambiae.

Numerous studies have examined changes in transcript levels after Anopheles gambiae takes a blood meal. Marinotti et al. (2006) used microarrays and reported massive changes in transcript levels 3 h after feeding (BF3h) compared to non-blood fed (NBF). We were intrigued by the number of transcripts for structural cuticular proteins (CPs) that showed such major differences in levels and employed paired-end (50 bp) RNA-seq technology to compare whole body transcriptomes from 5-day-old females NBF and BF3h. We detected transcripts for the majority of CPs (164/243) but levels of only 12 were significantly altered by the blood meal. While relative transcript levels of NBF females were somewhat similar to the microarray data, there were major differences in BF3h animals, resulting in levels of many transcripts, both for CPs and other genes changing in the opposite direction. We compared our data also to other studies done with both microarrays and RNA-seq. Findings were consistent that a small number of CP genes have transcripts that persist even in 5-day-old adults. Some of these transcripts showed diurnal rhythms (Rund et al., 2013; Rinker et al., 2013). In situ hybridization revealed that transcripts for several of these CP genes were found exclusively or predominantly in the eye. Transcripts other than for CPs that changed in response to blood-feeding were predominantly expressed in midgut and Malpighian tubules. Even in these tissues, genes responsible for proteins with similar functions, such as immunity or digestion, responded differently, with transcript levels for some rising and others falling. These data demonstrate that genes coding for some CPs are dynamic in expression even in adults and that the response to a blood meal is rapid and precisely orchestrated.

CPF and CPFL, two related gene families encoding cuticular proteins of Anopheles gambiae and other insects.

Cuticular proteins (CPs) are structural proteins of insects as well as other arthropods. Several CP families have been described, among them a small family defined by a 51 amino acid motif [Andersen, S.O., Rafn, K., Roepstorff, P., 1997. Sequence studies of proteins from larval and pupal cuticle of the yellow meal worm, Tenebrio molitor. Insect Biochem. Mol. Biol. 27, 121-131]. We identified four proteins of this family in Anopheles gambiae that we have named CPF. We have also identified CPFs from other insects by searching databases. Alignment of these CPF proteins showed that the conserved region is only 44 aa long and revealed another conserved motif at the C-terminus. A dendrogram divided the CPF proteins into four groups, one basal and three specialized. We also identified several proteins of another CP family, CPFL, which has similarities to CPFs. CPFs and CPFLs share some protein motifs. Expression studies with real-time qRT-PCR of the A. gambiae CPFs and CPFLs showed that the four CPFs and one CPFL gene are expressed just before pupal or adult ecdysis, suggesting that they are components of the outer layer of pupal and adult cuticles. The other CPFLs appear to contribute to larval cuticle. Recombinant CPF proteins did not bind to chitin in the assay we used.