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Molecular cloning, characterization and regulation of the cockroach vitellogenin receptor during oogenesis
Author(s) -
Tufail M.,
Takeda M.
Publication year - 2005
Publication title -
insect molecular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.955
H-Index - 93
eISSN - 1365-2583
pISSN - 0962-1075
DOI - 10.1111/j.1365-2583.2005.00570.x
Subject(s) - vitellogenin , biology , vitellogenesis , oogenesis , oocyte , complementary dna , microbiology and biotechnology , messenger rna , northern blot , western blot , medicine , gene , genetics , embryo
The vitellogenin receptor (VgR) belongs to the low density lipoprotein receptor (LDLR) superfamily, and mediates the uptake of vitellogenin (Vg) into developing oocytes of all oviparous species. We cloned and characterized a VgR from previtellogenic ovaries of the cockroach, Periplaneta americana ( Pa ). This is the first report on a VgR from a hemimetabolous insect. The cDNA, comprising 5722 bp, encoded a 1790‐residue mature protein with a predicted molecular mass of 200.5 kDa. We next characterized the ovarian expression pattern, developmental regulation and cellular distribution of the VgR mRNA and protein. Northern blot analysis confirmed that a ∼7.2 kb transcript was specifically expressed in ovarian tissues at high levels throughout ovarian development, especially in previtellogenic ovaries and in ovaries before adult emergence. RNA in situ hybridization and immunocytochemistry localized the VgR mRNA and protein to germ‐line derived cells, the oocytes, and revealed that VgR gene transcription and translation begin very early during oocyte differentiation in the germarium. Immunoblot analysis detected an ovary‐specific VgR protein of ∼210 kDa that was present in previtellogenic ovaries on the day of female emergence. The VgR protein signal strengthened every day and was intense after initiation of vitellogenesis and onset of Vg uptake. The immunoblotting of vitellins demonstrated that Vg uptake occurred on day 5, one day after Vg first appeared in the haemolymph, indicating that the receptor‐endocytotic machinery starts functioning soon after the ligand becomes available.