A knockdown in the expression of a male‐specific aminopeptidase impedes the male reproductive success of the mosquito <i>Culex pipiens</i>

It is imperative to determine the expression patterns and functions of genes essential for reproduction in mosquito vectors, such as <i>Culex pipiens</i>, to optimize vector control strategies, such as the sterile insect technique (SIT). The reproductive organs of mosquitoes are responsible for various processes, including spermatogenesis, seminal fluid secretion, and female insemination during mating. Using Illumina RNA-seq and qRT-PCR validation, this study aimed to identify and categorize genes associated with the male accessory glands, as well as potentially other reproductive structures, of <i>Cx. pipiens</i>. Analysis of young and old male accessory gland tissues revealed 345 and 26 upregulated transcripts, respectively. Further qRT-PCR analysis showed that six genes were highly upregulated in old male accessory gland (MAG) tissue, including <i>dual specificity mitogen-activated protein kinase hemipterous</i>, <i>atrial natriuretic peptide receptor</i>, and <i>zinc-binding dehydrogenase</i>. Additionally, 17 genes were found to be highly upregulated in young MAG tissue with some of them speculated to have reproductive functions; among the notably upregulated genes were those encoding <i>heterogeneous nuclear ribonucleoprotein</i>, <i>protein cluster segregational</i>, and two <i>cytosol aminopeptidases</i>. The function of <i>cytosol aminopeptidase</i> (CPIJ003539) has been validated in male <i>Cx. pipiens</i> through in-cage insemination and fertility assays, revealing that females mated with <i>dsi-aminopeptidase</i> knockdown males had impaired sperm storage and egg production abilities. These findings provide promising prospects for the development of targeted vector control strategies for <i>Culex</i> mosquitoes to achieve more successful outcomes concerning efficient reduction of the pest populations.