Author/EditorEldesoky, Marwa Said Abdelhalem
Alternative Titleクルマエビのビテロジェニン遺伝子に関する研究：新規ビテロジェニンの同定とホルモンによる発現制御
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The reproductive biology of crustaceans is of great importance for the fisheries and aquaculture industries. Vitellogenesis, the process of yolk formation, is a critical factor in reproduction for both oviparous vertebrates and invertebrates. Vitellogenin (Vg) is the precursor of the major egg-yolk protein, hence is used as a marker of vitellogenesis. The kuruma prawn Marsupenaeus japonicus is an economically important fisheries species in Japan and several Southeast Asian countries. A single Vg gene, known as Maj-Vg1, was identified in this species, and the hepatopancreas, and ovary were recognized as Vg synthesis sites based on its gene expression pattern. The Maj-Vg1 expression in the ovary was inhibited by the vitellogenesis-inhibiting hormone produced by the eyestalk ganglia. However, the presence of multiple Vg genes, recently reported in some decapods, and the hormonal regulation of Vg gene expression in the hepatopancreas is still ambiguous. Therefore, in this thesis, the search for a novel Vg gene from the transcriptome data of the hepatopancreas was conducted, and the relationship between its gene expression and the progression of vitellogenesis was also examined. Furthermore, the effects of various hormones on Vg gene expression in hepatopancreas were studied using ex-vivo assays to gain a deeper understanding of vitellogenesis in this species. The full-length cDNA sequence for the novel vitellogenin, Maj-Vg2 was successfully identified. The deduced Maj-Vg2 is composed of 2,554 amino acid residues. Amino acid sequence similarity between Maj-Vg1 and Maj-Vg2 was 54%. The phylogenetic analysis demonstrated that Maj-Vg2 forms a distinct clade with Vg2 of several Penaeus species, such as Metapenaeus ensis, Fenneropenaeus merguiensis, and Litopenaeus vannamei, separate from the clade containing Vg1 and Vg3 of these species. The expression of Maj-Vg2 was restricted to the hepatopancreas. Maj-Vg2 showed low expression during the previtellogenic stage, then increased during the early and late yolk globule stages of wild prawns. Moreover, eyestalk ablation significantly induced Maj-Vg2 expression in immature prawns. This result was similar to the increase in Maj-Vg1 expression observed in the ovary, indicating that Maj-Vg2 is involved in vitellogenesis and may play a complementary role in yolk protein synthesis during ovarian development. A vertebrate-type sex steroid hormone estradiol and the crustacean homolog of insect juvenile hormone methyl farnesoate show no significant effect on gene expression of both MajVg1 and Maj-Vg2 in the hepatopancreas. However, the synthetic insulin-like peptide (ILP1) significantly increased the expression levels of the two Vgs in the hepatopancreas of adolescent prawns. Specifically, Maj-Vg1 expression was significantly upregulated with 1 µM ILP1, 1.3-fold higher in average relative value to control. Maj-Vg2 expression was induced with 0.1 and 1 µM, 1.2- and 1.3-fold higher to control, respectively. In the ovaries of adolescent and immature adult prawns, only 0.1 µM ILP1 upregulates Maj-Vg1 expression, 1.5- and 2.2-fold higher than the control, respectively. These results suggest that the ovarian-specific ILP1 is likely involved in regulating vitellogenesis in M. japonicus. Overall, this is the first study focusing on the identification of novel vitellogenin Maj-Vg2 in M. japonicus and hormonal regulation of the gene expression of Vgs by ILP1.
本文/Graduate School of Bioresources,Mie University, Japan
121p
Collection (particular)国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
Date Accepted (W3CDTF)2023-12-15T22:13:25+09:00
Data Provider (Database)国立国会図書館 : 国立国会図書館デジタルコレクション