Identification and characterization of seminal fluid proteins in the Asian tiger mosquito, Aedes albopictus

Abstract

The Asian tiger mosquito (Aedes albopictus) is an important vector for pathogens that affect human health, including the viruses that cause dengue and Chikungunya fevers. It is also one of the world's fastest-spreading invasive species. For these reasons, it is crucial to identify strategies for controlling the reproduction and spread of this mosquito. During mating, seminal fluid proteins (Sfps) are transferred from male mosquitoes to females, and these Sfps modulate female behavior and physiology in ways that influence reproduction. Despite the importance of Sfps on female reproductive behavior in mosquitoes and other insects, the identity of Sfps in Ae. albopictus has not previously been reported. We used transcriptomics and proteomics to identify 198 Sfps in Ae. albopictus. We discuss possible functions of these Sfps in relation to Ae. albopictus reproduction-related biology. We additionally compare the sequences of these Sfps with proteins (including reported Sfps) in several other species, including Ae. aegypti. While only 72 (36.4%) of Ae. albopictus Sfps have putative orthologs in Ae. aegypti, suggesting low conservation of the complement of Sfps in these species, we find no evidence for an elevated rate of evolution or positive selection in the Sfps that are shared between the two Aedes species, suggesting high sequence conservation of those shared Sfps. Our results provide a foundation for future studies to investigate the roles of individual Sfps on feeding and reproduction in this mosquito. Functional analysis of these Sfps could inform strategies for managing the rate of pathogen transmission by Ae. albopictus.

Figure 1. Functional categories of Aedes albopictus lower reproductive tract transcripts and seminal fluid proteins.

Numbers indicate the percent of transcripts associated with the functional category. A. Transcripts found only in males (accessory glands and seminal vesicles; 3,980 total); B. Transcripts found only in females (lower reproductive tract; 7,576 total); C. Transcripts found in both males and females (17,947 total); D. Seminal fluid proteins (198 total).

Figure 2. Estimation of evolutionary rates of Aedes albopictus seminal fluid proteins and control proteins.

A. Evolutionary rates of nonsynonymous (dN) versus synonymous (dS) changes for Ae. albopictus Sfps (72 total); B. Evolutionary rates of nonsynonymous (dN) versus synonymous (dS) changes for Ae. albopictus control proteins (3495 total; 188 not shown due to extreme values of dN or dS). For both panels, the solid line shows a regression line, and the dashed line gives a 1∶1 dN/dS ratio, with points falling above the line showing dN/dS >1.