Dynamics of vitellogenin mRNA expression during vitellogenesis in the banana shrimp Penaeus (Fenneropenaeus) merguiensis using real‐time PCR

Abstract

An open reading frame (ORF) of vitellogenin (Vg) cDNA was amplified from the ovaries of the banana shrimp, Penaeus merguiensis. An examination of Vg-deduced amino acid sequence revealed the presence of cleavage sites at a consensus motif for subtilisin-like endoproteases prior to the N-terminal sequences of purified vitellin (Vt) subunits. A comparison of the primary structures of Vg molecules in decapod crustacean species revealed the existence of a common characteristic structure, and phylogenetic analysis reflected the current taxonomic classifications of crustaceans. A PCR product of 1.1 kb encoding the 3'-end of Vg cDNA was cloned from the hepatopancreas. Although its sequence was almost identical to that of the same region of the ovarian Vg, with only 18 nucleotide differences, analysis suggests that they have been subjected to natural selection, indicating that there may be two different, tissue-specific Vg genes in P. merguiensis. This is consistent with the different expression patterns of Vg mRNA, as determined by real-time PCR. Vg mRNA levels were maintained at low levels during the previtellogenic stage and they increased as vitellogenesis progressed to reach a peak at the early vitellogenic stage in the ovary or at the vitellogenic stage in the hepatopancreas, and thereafter, levels decreased. Expression of Vg mRNA was much higher in the ovary compared to the hepatopancreas at all stages of ovarian development, implying that the ovary is mainly responsible for Vt synthesis. These indicate that penaeids constitute a unique model for vitellogenesis, showing intraovarian gene expression and synthesis of yolk protein.

Mechanisms and control of vitellogenesis in crustaceans

“…Interestingly, in species such as M. japonicus and P. semisulcatus, one and the same Vg is expressed in the ovary and hepatopancreas [16,17]. However, in other species, such as Litopenaeus merguiensis, M. ensis and P. monodon, more than one Vg may be involved in the tissue-specific expression of the gene in both the ovary and hepatopancreas [18][19][20]. Especially in L. merguiensis, the patterns of Vg mRNA expression between the hepatopancreas and ovary differ in that the expression level in the hepatopancreas is much lower than that in the ovary at all stages of ovarian development [18].…”

“…However, in other species, such as Litopenaeus merguiensis, M. ensis and P. monodon, more than one Vg may be involved in the tissue-specific expression of the gene in both the ovary and hepatopancreas [18][19][20]. Especially in L. merguiensis, the patterns of Vg mRNA expression between the hepatopancreas and ovary differ in that the expression level in the hepatopancreas is much lower than that in the ovary at all stages of ovarian development [18]. Evidently, the relative contributions of the ovary and hepatopancreas to overall yolk production may differ among various shrimp species.…”

Reproductive Mechanisms in Crustacea Focusing on Selected Prawn Species: Vitellogenin Structure, Processing and Synthetic Control

“…monodon (Tiu et al 2006b), Fe. merguiensis (Phiriyangkul et al 2007), and Fenneropenaeus chinensis (Xie et al 2009) by Northern hybridization or RT-PCR analysis. The vitellogenin genes expressed in the hepatopancreas and ovary were identical in Mar.…”

“…In fact, two vitellogenin genes, MeVg1 and MeVg2, were cloned in the sand shrimp Metapenaeus ensis; MeVg1 was expressed in both organs, whereas MeVg2 was expressed only in the hepatopancreas (Tsang et al 2003;Kung et al 2004); and multiple vitellogenin genes are also presumed to exist in Fe. merguiensis (Phiriyangkul et al 2007). Detailed localization of vitellogenin mRNA was examined by in situ hybridization in Mar.…”

“…vannamei (Raviv et al 2006), Fe. merguiensis (Phiriyangkul et al 2007), and Me. ensis (for MeVg1; Tiu et al 2006a).…”