Submitted October 26, 2007
Returned for revision November 20, 2007
Accepted January 8, 2008
Ovary
From Hepatopancreas to Ovary: Molecular Characterization of a Shrimp Vitellogenin Receptor Involved in the Processing of Vitellogenin
Shirley Hiu Kwan Tiu ,
John Benzie ,
and
Siu-Ming Chan *
* To whom correspondence should be addressed. E-mail: chansm{at}hkucc.hku.hk.
Abstract
We report the first cloning and characterization of cDNA encoding a putative vitellogenin receptor (PmVgR) from the shrimp Penaeus monodon. PmVgR cDNA is 6.8 kb, the deduced protein has 1943 amino acids with a molecular weight of 211 kDa. PmVgR is ovary specific and consists of conserved cysteine-rich domains, epidermal-growth factor like (EGF-like) domains and YWTD motifs similar to the low density lipoprotein (LDL), very low density lipoprotein (VLDL) and vitellogenin (VgR) receptors of the insects and the vertebrates. PmVgR expression level in the ovary is low during early vitellogenesis and increases to maximum level in females with gonadosomatic index of 3-4, presumably when needed for receptor mediated endocytosis during the rapid phase of extra-ovarian vitellogenin production by the hepatopancreas. A peptide from the C-terminal end of PmVgR was synthesized for antibody production. Anti-PmVgR antibody recognized an ovarian membrane protein. The level of this protein is high when extra-ovarian production of PmVg reaches peak level. By immunohistochemical analysis, PmVgR was detected strongly in the membranes of larger oocytes. PmVgR expression was knocked-down in shrimp after they were injected with PmVgR dsRNA, leading to a decrease in PmVgR protein content in the ovary but an increase in the hemolymph level of vitellogenin. This study represents the first report for the functional analysis of a putative vitellogenin receptor in a crustacean.
Key words:
Ovary •
Gene regulation •
receptor mediated endocytosis •
vitellogenesis •
vitellogenin receptor
