Structural Similarity and Expression Differences of Two Pj-Vg Genes from the Pandalus Shrimp Pandalopsis japonica

Abstract

Vitellogenin (Vg) is the precursor of vitellin (Vn), which is the major yolk protein in nearly all oviparous species, including fish, amphibians, reptiles, and most invertebrates. It is one of the most important factors during reproduction, and numerous studies have shown that Vg genes are markers of the reproductive cycle and effecter genes induced by endocrine-disrupting chemicals (EDCs). Previously, we isolated two distinct cDNAs encoding vitellogenin homologs Pj-Vg1 and Pj-Vg2 from Pandalus shrimp Pandalopsis japonica. In this study, full-length genomic sequences of Pj-Vg1 and Pj-Vg2 were determined using a PCR-based genome walking strategy. Isolated Pj-Vg1 and Pj-Vg2 genes were 11,910 and 11,850 bp long, respectively. Both Pj-Vg genes had 15 exons and 14 introns, and the splicing sites were also the same, suggesting that they arose via gene duplication. The similar structural characteristics of decapod Vg genes suggest that they are all orthologs that evolved from the same ancestral gene. Analysis of Pj-Vg1 and Pj-Vg2 expression revealed that the relative copy numbers of Pj-Vg1 and Pj-Vg2 were similar in the hepatopancreas, whereas Pj-Vg2 transcripts were also detected in the ovary. Expression of both Pj-Vg genes was induced in hepatopancreas of mature individuals, whereas only Pj-Vg2 transcripts were upregulated in the ovaries from mature animals, suggesting that both Pj-Vgs are important for oocyte development. A strong positive correlation was found between Pj-Vg1 and Pj-Vg2 transcripts in the same individual, indicating they are under the same control mechanisms. Additionally, a positive correlation was found between ovarian and hepatopancreatic Pj-Vg2 transcripts, suggesting that its dual expression is regulated by similar physiological conditions. Knowledge of the similarities and differences between the two vitellogenin-like genes, Pj-Vg1 and Pj-Vg2, would help us to understand their roles in reproduction and other physiological effects.

Full-Length Transcriptome Sequencing and Comparative Transcriptomic Analysis Provide Insights Into the Ovarian Maturation of Exopalaemon carinicauda

“…Metapenaeus ensis (Kung et al, 2004) and Pandalopsis japonica (Jeon et al, 2011) have indicated the presence of multiple Vtg genes. In this study, five EcVtgs were identified in the fulllength transcripts, which were expressed in the ovaries at different ovarian developmental stages.…”

Genome-Wide Identification of Vitellogenin Gene Family and Comparative Analysis of Their Involvement in Ovarian Maturation in Exopalaemon carinicauda

“…Understanding the differences between variation of Vtg in mechanisms of yolk formation and processing is a benefit for the regulation of ovarian maturation and embryos and larvae development. Similar to in fish, previous studies on Metapenaeus ensis [14] and Pandalopsis japonica [15] have suggested the presence of multiple Vtg genes in these crustaceans, while most studies on the function of the Vtg gene in crustaceans have concentrated on a single Vtg gene. Meanwhile, the function of different vitellinogen genes in nutritional and non-nutritional roles in crustaceans has been little studied.…”

“…Furthermore, variations within the conserved motifs of Vtg genes ranged from 26 to 30. Typically, a 15-exon Vtg gene has been reported in shrimp species, including M. ensis [37], P. monodon [38], Homarus americanus [39], and P. japonica [15]. Across these reports, the sizes and positions of exons and introns within the Vtg gene remained consistent, indicating a high level of conservation among decapod Vtg genes.…”