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

Dendroctonus armandi (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 Dendroctonus armandi plays a significant role in the reproduction of its population. In recent years, the role of the fem-1 gene in sex determination in other insects has been reported. However, the function and expression of the fem-1 gene in Dendroctonus armandi remain uncertain. In this study, three fem-1 genes were cloned and characterized. These were named Dafem-1 A, Dafem-1 B, and Dafem-1 C, respectively. The expression levels of these three Dafem-1 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 Dafem-1 genes at different developmental stages and between males and females. Furthermore, injection of double-stranded RNA (dsRNA) targeting the expressions of the Dafem-1 A, Dafem-1 B, and Dafem-1 C genes resulted in increased mortality, deformity, and decreased emergence rates, as well as an imbalance in the sex ratio. Following the interference with Dafem-1 A and Dafem-1 C, no notable difference was observed in the expression of the Dafem-1 B gene. Similarly, after the interference with the Dafem-1 B gene, no significant difference was evident in the expression levels of the Dafem-1 A and Dafem-1 C genes. However, the interference of either the Dafem-1 A or Dafem-1 C gene results in the downregulation of the other gene. The aforementioned results demonstrate that the Dafem-1 A, Dafem-1 B, and Dafem-1 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 Dafem-1 A, Dafem-1 B, and Dafem-1 C genes. This provides a crucial theoretical foundation for further elucidating the sex determination mechanism of Dendroctonus armandi .