Conserved molecular pathways underlying biting in two divergent mosquito genera

Abstract

Mosquitoes transmit a wide variety of devastating pathogens when they bite vertebrate hosts and feed on their blood. However, three entire mosquito genera and many individual species in other genera have evolved a nonbiting life history in which blood is not required to produce eggs. Our long-term goal is to develop novel interventions that reduce or eliminate the biting behavior in vector mosquitoes. A previous study used biting and nonbiting populations of a nonvector mosquito, Wyeomyia smithii, as a model to uncover the transcriptional basis of the evolutionary transition from a biting to a nonbiting life history. Herein, we ask whether the molecular pathways that were differentially expressed due to differences in biting behavior in W. smithii are also differentially expressed between subspecies of Culex pipiens that are obligate biting (Culex pipiens pipiens) and facultatively nonbiting (Culex pipiens molestus).Results from RNAseq of adult heads show dramatic upregulation of transcripts in the ribosomal protein pathway in biting C. pipiens, recapitulating the results in W. smithii, and implicating the ancient and highly conserved ribosome as the intersection to understanding the evolutionary and physiological basis of blood feeding in mosquitoes.Biting Culex also strongly upregulate energy production pathways, including oxidative phosphorylation and the citric acid (TCA) cycle relative to nonbiters, a distinction that was not observed in W. smithii. Amino acid metabolism pathways were enriched for differentially expressed genes in biting versus nonbiting Culex. Relative to biters, nonbiting Culex upregulated sugar metabolism and transcripts contributing to reproductive allocation (vitellogenin and cathepsins). These results provide a foundation for developing strategies to determine the natural evolutionary transition between a biting and nonbiting life history in vector mosquitoes.

MicroRNA Expression Prior to Biting in a Vector Mosquito Anticipates Physiological Processes Related to Energy Utilization, Reproduction and Immunity

“…Of these eight miRNAs, six have validated functions or predicted mRNA targets related to energy utilization, reproduction, and immunity. Differences in the expression of miRNAs promoting energy utilization in the head tissues of biting Pipiens relative to non-biting Molestus are consistent with previous studies at the mRNA level of these same tissues [14], as well as studies of the head tissues of A. aegypti before attaining competency for blood feeding [4]. Taken together, these results emphasize the dramatic energetic investment that is required for blood-feeding mosquitoes to locate a blood-meal host and acquire blood.…”

“…These results imply increased Tret1 protein levels in non-biting Molestus relative to biting Pipiens. Taken together with our previous mRNA results showing upregulation of fructose and mannose metabolism in non-biting Molestus [14] and the established role of sugar feeding in supporting autogenous reproduction [16], these results imply that non-biting Molestus prioritize sugar metabolism to generate sufficient energy reserves to reproduce without a blood meal.…”

“…The predicted target of miR-1891 is trehalose transporter1 (Tret1) (Supplementary Datafile online). Consistent with the differential expression of miR-1891, our previous analyses of mRNAs showed that the expression of the Tret1 transcript was lower in biting Pipiens than in non-biting Molestus [14]. These results imply increased Tret1 protein levels in non-biting Molestus relative to biting Pipiens.…”

“…Our results are distinct from previous results on the role of miRNAs in blood-feeding related processes because they reflect anticipatory responses before blood-feeding rather than downstream responses after blood has been ingested. Similar to our previous study of mRNAs [14], we identified several differentially expressed miRNAs that are implicated in energy utilization. Furthermore, in agreement with previous studies of mosquito miRNA expression in response to blood feeding, we also identified differentially expressed miRNAs implicated in physiological processes related to immunity and reproduction.…”

An inquiline mosquito modulates microbial diversity and function in an aquatic microecosystem

“…A positive correlation between mosquito larval abundance and hydrolysis of l ‐phenylalanine suggests that W. smithii larvae may affect amino acid turnover in pitcher communities, particularly of a metabolically expensive aromatic essential metabolite for which bacteria are frequently auxotrophic (D'Souza et al., 2014; Zengler & Zaramela, 2018). In addition to the potential implications for the composition and underlying interactions of pitcher‐associated communities, phenylalanine, along with tyrosine, has previously been identified as a key metabolite in the metabolism of non‐blood‐feeding relative to blood‐feeding subspecies of the common house mosquito, Culex pipiens (Beintema et al., 1994; Siperstein et al., 2022; Wheeler & Buck, 1996). Whether phenylalanine hydrolysis is also important for the maintenance of a non‐blood‐feeding life history in W. smithii warrants further study, especially in light of results from a previous study that failed to detect differences in phenylalanine metabolism between blood‐feeding and non‐blood‐feeding W. smithii populations (Bradshaw et al., 2018).…”