Abstract
The COP9 signalosome (CSN) is an evolutionarily conserved multi-subunit complex that plays crucial roles in regulating various biological processes in plants, mammals, and the model insect Drosophila. However, it is poorly studied in non-model insects, whereas its role in fecundity remains unclear. In this study, all nine CSN subunits were identified and characterized in Bactrocera dorsalis, a major invasive agricultural tephritid pest. Each subunit gene, except for csn9x1, encoded a protein containing a PCI/PINT or MPN domain. Phylogenetic analysis revealed that all CSN subunits were individually clustered into a specific branch with their counterparts from other species. All CSN subunit genes were expressed in all detected developmental stages and tissues. Most subunits, except for csn8 and csn9x1, showed the highest expression level in the eggs. Notably, csn3 and csn5 were significantly enriched in mature female adults. Further analysis of csn3 revealed that it was enriched in the ovary and that its ovarian expression level gradually increased with the reproductive development process. RNAi-based knockdown of csn3 in female adults significantly reduced the number of laid eggs. The expression level of EcRB1 and USP, which encode the heterodimer receptors of 20E, and vitellogenin transcripts (Vg1 and Vg2) was suppressed in the fat body of female adults injected with csn3dsRNA. Decreased level of Vg1 protein was confirmed by means of Western blots. These data indicate that csn3 is involved in female reproduction by regulating 20E signaling and Vg synthesis. Overall, our study may facilitate the development of new strategies for controlling B. dorsalis since it provides insights into the evolution and expression patterns of all CSN subunit genes as well as the critical roles of csn3 in female fecundity.
Highlights
The COP9 signalosome (CSN) is an evolutionarily conserved multi-subunit complex that was originally identified in Arabidopsis for the suppression of photomorphogenesis (Wei et al, 1994; Wei and Deng, 2003) and discovered in a wide range of eukaryotic organisms, including plants, yeast, mammals, and insects (Henke et al, 1999; Oron et al, 2002; Zhou et al, 2003; Tong et al, 2015)
Each CSN subunit of B. dorsalis was first clustered in the same group with their counterparts in C. capitata, which was consistent with the nearest evolutionary distance of these two species in Tephritidae
The expression profile analysis of all subunits in the B. dorsalis COP9 signalosome showed that CSN is abundantly expressed in mature female adults
Summary
The COP9 signalosome (CSN) is an evolutionarily conserved multi-subunit complex that was originally identified in Arabidopsis for the suppression of photomorphogenesis (Wei et al, 1994; Wei and Deng, 2003) and discovered in a wide range of eukaryotic organisms, including plants, yeast, mammals, and insects (Henke et al, 1999; Oron et al, 2002; Zhou et al, 2003; Tong et al, 2015). COP9 Signalosome Subunit Genes in Bactrocera dorsalis by interacting with various signaling factors, CSN was considered to have diverse roles in various cellular and developmental processes (Wei and Deng, 2003), including deneddylation (Schwartz and Hochstrasser, 2003), DNA repair (Groisman et al, 2003; Holmberg et al, 2005), cell cycle regulation (Menon et al, 2007; Panattoni et al, 2008), and gene expression (Panattoni et al, 2008). CSN5 (or c-Jun activation domainbinding protein, JAB1) has been reported as the catalytic center for deneddylation of the Nedd8-cullin in the CSN complex that exists as monomer or a CSN5-containing small complex and plays various roles in HIF1-a stabilization, p27 nuclear export and degradation, E2F1-mediated apoptosis, cell cycle control, and cancer (Wei et al, 2008; Shackleford and Claret, 2010). Little is known regarding the comprehensive expression profiling of CSN subunits in these species
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