Vitelline membrane protein gene ZcVMP26Ab and its role in preventing water loss in Zeugodacus cucurbitae (Coquillett) embryos

Vitelline membrane proteins (VMPs) are major components of the vitelline membrane, which is an essential component of insect eggshell. The melon fly, Zeugodacus cucurbitae (Coquillett), is a destructive pest of many fruits and vegetables. Here, we identified and characterized three VMP genes in Z. cucurbitae, including ZcVMP26Aa, ZcVMP26Aalike, and ZcVMP26Ab. The open reading frames of ZcVMP26Aa, ZcVMP26Aa-like, and ZcVMP26Ab contained 384, 348, and 438 bp, encoding 127, 115, and 145 amino acid residues, respectively. A signal peptide was predicted in the 5'-end of each ZcVMPs. A conserved domain was also predicted within the three ZcVMPs. A phylogenetic tree of insect VMPs showed that the ZcVMPs are closely related to VMPs in Drosophila melanogaster. Spatiotemporal expression analyses showed that all three genes were highly expressed in adult females especially during the vitellogenesis period. Among the different tissues examined, the three genes only had high expression in the ovary. Suppression of the ZcVMP26Ab transcription by RNA interference significantly decreased the target gene expression and resulted in the increased desiccation and low hatchability of newly laid eggs. This indicated an important role of ZcVMP26Ab in preventing water loss in Z. cucurbitae embryos.