BdTTLL3B-mediated polyglycylation is involved in the spermatogenesis in Bactrocera dorsalis.

Polyglycylation is a post-translational modification that generates glycine side chains in the C-terminal domains of both α- and ß-tubulins. To date, the patterns and significance of polyglycylation across insect species remain largely unknown. The TTLL3B was thought to be a polyglycylase and be essential for polyglycylation in dipteran insects. In this study, the TTLL3B of Bactrocera dorsalis (BdTTLL3B) was identified and characterized. The BdTTLL3B expressed remarkably higher in adult males, especially in testes. The spatio-temporal patterns of polyglycylation were consistent with that of BdTTLL3B. Along with spermatogenesis, the intensity of polyglycylation was enhanced steadily and concentrated in elongated flagella. The expression of recombinant BdTTLL3B in Hela cells, which are genetically deficient in polyglycylation, catalyzed intracellular polyglycylation, validating the identity of BdTTLL3B as a polyglycylase. Knockout of BdTTLL3B significantly suppressed polyglycylation in testes and impaired male fertility, probably due to abnormal morphology of mitochondrial derivatives and over-accumulation of paracrystalline. Taken together, these findings indicated that the BdTTLL3B-mediated polyglycylation is involved in the spermatogenesis and play an important role in fertility of adult B. dorsalis. Therefore, the BdTTLL3B can be considered as a candidate target gene for the management of B. dorsalis, such as developing gene silencing/knockout-based sterile insect technology (SIT).

Transcriptomic Identification and Characterization of Trehalose-6-Phosphate Synthase in Fat Body of the Oriental Fruit Fly, Bactrocera dorsalis.

The destructive agricultural pest oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), has been causing huge damage to the fruits and vegetable industry. Although many pertinent studies have been conducted on B. dorsalis, the functions of fat body still remain largely unknown. To this end, the comparative transcriptome analysis between fat body and carcass was performed in an attempt to provide insights into functions of fat body of B. dorsalis in the present study. A total of 1431 upregulated and 2511 downregulated unigenes were discovered in the fat body vs carcass comparison, respectively. The enrichment analysis of differentially expressed genes (DEG) revealed that most of the enriched pathways were related to metabolism. The reliability of DEG analysis was validated by qRT-PCR measurements of 12 genes in starch and sucrose metabolism pathway, including the trehalose-6-phosphate synthase (BdTPS) which was highly expressed in eggs, 5 d-old adults, and fat body. The RNAi of BdTPS significantly affected trehalose and chitin metabolism, larval growth, and larva-pupa metamorphosis. Collectively, the findings in this study enriched our understanding of fat body functions in metabolism and demonstrated the indispensable roles of BdTPS in trehalose-related physiological pathways.

Validamycin Inhibits the Synthesis and Metabolism of Trehalose and Chitin in the Oriental Fruit Fly, Bactrocera dorsalis (Hendel).

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a notorious invasive pest that has raised concerns worldwide. Validamycin has been demonstrated to be a very strong inhibitor against trehalase in a variety of organisms. However, whether validamycin can inhibit trehalase activity to suppress trehalose hydrolysis and affect any other relevant physiological pathways in B. dorsalis remains unknown. In this study, the effects of validamycin injection on the synthesis and metabolism of trehalose and chitin were evaluated. The results show that validamycin injection significantly affected trehalase activity and caused trehalose accumulation. In addition, the downstream pathways of trehalose hydrolysis, including the synthesis and metabolism of chitin, were also remarkably affected as the expressions of the key genes in these pathways were significantly regulated and the chitin contents were changed accordingly. Intriguingly, the upstream trehalose synthesis was also affected by validamycin injection due to the variations in the expression levels of key genes, especially BdTPPC1. Moreover, BdTPPC1 was predicted to have a binding affinity to validamycin, and the subsequent in vitro recombinant enzyme activity assay verified the inhibitory effect of validamycin on BdTPPC1 activity for the first time. These findings collectively indicate that validamycin can be considered as a promising potential insecticide for the management of B. dorsalis.

Population Genetic Structure of Chlorops oryzae (Diptera, Chloropidae) in China.

Frequent outbreaks have made Chlorops oryzae one of the major pests of rice in some regions. In order to understand the ecological adaptation of C. oryzae at the molecular level, and provide a scientific basis for formulating management strategies, we used two molecular markers, COI and ITS1 sequences, to systematically analyze the genetic structure of 31 populations. The higher haplotype diversity and lower nucleotide diversity indicated that the C. oryzae populations experienced rapid expansion after a "Bottleneck effect". The results of the mismatch distribution, neutrality test (Fu's Fs < 0, p < 0.001), and haplotype network analysis suggested that the population has recently undergone an expansion. Although genetic differentiation among C. oryzae populations was found to have existed at low/medium levels (Fst: 0.183 for COI, 0.065 for ITS1), the frequent gene flow presented as well (Nm: 2.23 for COI, 3.60 for ITS1) was supposed to be responsible for frequent local outbreaks.