Fem-1 Gene of Chinese White Pine Beetle (Dendroctonus armandi): Function and Response to Environmental Treatments

<i>Dendroctonus armandi</i> (Tsai and Li) (Coleoptera: Curculionidae: Scolytinae) is regarded as the most destructive forest pest in the Qinling and Bashan Mountains of China. The sex determination of <i>Dendroctonus armandi</i> plays a significant role in the reproduction of its population. In recent years, the role of the <i>fem-1</i> gene in sex determination in other insects has been reported. However, the function and expression of the <i>fem-1</i> gene in <i>Dendroctonus armandi</i> remain uncertain. In this study, three <i>fem-1</i> genes were cloned and characterized. These were named <i>Dafem-1</i>A, <i>Dafem-1</i>B, and <i>Dafem-1</i>C, respectively. The expression levels of these three <i>Dafem-1</i> genes vary at different stages of development and between the sexes. In response to different environmental treatments, including temperature, nutrients, terpenoids, and feeding duration, significant differences were observed between the three <i>Dafem-1</i> genes at different developmental stages and between males and females. Furthermore, injection of double-stranded RNA (dsRNA) targeting the expressions of the <i>Dafem-1</i>A, <i>Dafem-1</i>B, and <i>Dafem-1</i>C genes resulted in increased mortality, deformity, and decreased emergence rates, as well as an imbalance in the sex ratio. Following the interference with <i>Dafem-1</i>A and <i>Dafem-1</i>C, no notable difference was observed in the expression of the <i>Dafem-1</i>B gene. Similarly, after the interference with the <i>Dafem-1</i>B gene, no significant difference was evident in the expression levels of the <i>Dafem-1</i>A and <i>Dafem-1</i>C genes. However, the interference of either the <i>Dafem-1</i>A or <i>Dafem-1</i>C gene results in the downregulation of the other gene. The aforementioned results demonstrate that the <i>Dafem-1</i>A, <i>Dafem-1</i>B, and <i>Dafem-1</i>C genes play a pivotal role in the regulation of life development and sex determination. Furthermore, it can be concluded that external factors such as temperature, nutrition, terpenoids, and feeding have a significant impact on the expression levels of the <i>Dafem-1</i>A, <i>Dafem-1</i>B, and <i>Dafem-1</i>C genes. This provides a crucial theoretical foundation for further elucidating the sex determination mechanism of <i>Dendroctonus armandi</i>.