RNAi-mediated knockdown of vitellogenin genes disrupts ovary development and alters ovarian bacterial composition in Zeugodacus tau (Diptera: Tephritidae).

Zeugodacus tau Walker (Diptera: Tephritidae) is an invasive pest of global significance that inflicts substantial losses to the fruit and vegetable production sectors annually. Despite the availability of the Z. tau genome in public database, functional characterization of key genes remained limited. Vitellogenin (Vg) functions as a key precursor of yolk protein and exerts a pivotal part in the insect reproductive process. Here, we identified 3 Vg genes (Vg1, Vg2, and Vg3) based on genetic data from Z. tau. Analysis of amino acid sequences demonstrated that all ZtVgs contain conserved serine residues, a putative cleavage site, and putative N-linked glycosylation sites. Molecular phylogenetic reconstruction revealed that ZtVgs exhibited the closest evolutionary affinity to their homologs found in Zeugodacus cucurbitae and Bactrocera dorsalis. Spatiotemporal expression profiling indicated that all 3 ZtVgs exhibit pronounced expression in the female fat body. Treatments with the Methoprene and 20-hydroxyecdysone (20E) significantly upregulated ZtVgs expression 24 h post application at a dose of 1 μg. RNA interference (RNAi) bioassay revealed that the suppression of 3 ZtVgs delayed ovary development and impaired female fertility. Further microbiome analysis revealed that knockdown of the 3 Vg genes led to reduced abundance of bacterial taxa affiliated with the phylum Pseudomonadota and the genus Burkholderia in the ovary. These findings elucidate the important function of Vgs in ovary development and provide insights into the association between insect Vg genes and the ovarian bacteria, thereby establishing a groundwork for subsequent investigations on the molecular mechanisms underlying their interaction.