Ovarian development and role of vitellogenin gene in reproduction of the tomato leaf miner Tuta absoluta

Vitellogenin (Vg) is a glycolipid complex protein produced by the fat body of female insects. It plays vital roles in oocyte development and helps regulate reproductive development. In this study, we determined the grading criteria for ovarian development and identified a Vg gene (designated TaVg) from the devastating invasive pest, Tuta absoluta (Meyrick). TaVg contains a 5208 bp open reading frame encoding a protein of 1735 amino acids that includes conserved domain structures of insect Vg. Phylogenetic analysis indicated that TaVg was clustered into a clade with the Vg of other Lepidoptera species, suggesting this gene has been conserved during evolution. Spatiotemporal expression analyses showed that TaVg was highly expressed in the female pupae and adults. There was increased expression during sexual maturation, and the high expression level was found in the ovary and fat body. RNAi-mediated silencing of TaVg resulted in significant downregulation of vitellogenin contents and severely affected ovarian development. Females injected with dsTaVg had shorter ovarian tubes and fewer oocytes compared with the untreated individuals. The number of oocytes and the amount of yolk deposition in the egg chambers also reduced. Depletion of TaVg significantly reduced the number of eggs laid and the hatching rate. Co-silencing of TaVg and TaVgR had a more significant effect on inhibiting the ovarian development and reducing female fecundity of T. absoluta, showing that the two genes play important role in regulating the reproduction. Our results provide potential targets for developing RNAi-based pest management tractic on T. absoluta.