Diallyl Trisulfide, an Active Substance from Garlic, Inhibits Female Oviposition by Decreasing the Expression of the <i>OCT</i> Gene, which is Highly Expressed in the Spermathecal Gland of <i>Sitotroga cerealella</i> (Oliver)

Diallyl trisulfide (DAT) effectively inhibits the fecundity of <i>Sitotroga cerealella</i>. <i>Organic cation transporter</i> (<i>OCT</i>) was most highly expressed in the spermathecal gland of female moths and was significantly decreased after DAT fumigation. However, the function of OCT in insect reproduction has been rarely reported. In this study, after silencing <i>OCT</i> in female adults, the mating rate, oviposition, and number of sperm transferred to females were decreased significantly, and transfer time of sperm in the female was delayed. Meanwhile, the long and short waves formed during sperm movement became longer, which lead sperm to take a longer time to complete a movement cycle. Finally, 5-hydroxytryptamine (5-HT) was significantly increased. Conversely, triacylglycerol (TG) decreased significantly. The expression of the 5<i>-HT</i> 2<i>A</i> receptor gene, which is highly expressed in the abdomen, was significantly decreased. The findings have provided a theoretical basis for explaining the inhibitory effect of garlic essential oil on the reproduction of <i>S. cerealella</i>.