The vitellogenin cDNA of Cherax quadricarinatus encodes a lipoprotein with calcium binding ability, and its expression is induced following the removal of the androgenic gland in a sexually plastic system
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Abstract
Oocyte maturation in decapod crustaceans is a two step process. Primary vitellogenesis
is followed by a variable hiatus that lasts up to the onset of secondary vitellogenesis,
which is marked by the rapid accumulation of yolk proteins in the oocytes. We have
cloned a complete Cherax quadricarinatus vitellogenin cDNA. The sequenced cDNA contains
a 2584 aa open reading frame which shows sequence similarity to vitellogenins from
other crustaceans. The mRNA encodes at least two of the previously identified vitellin
components, indicating that the primary translation product is subject to post-translational
modification, including proteolytic cleavage. The region close to the 3(') end of
the mRNA encodes a previously characterized negatively charged protein (provisionally
designated P(106)). We show here that the negative charge of P(106) could be due to
its ability to bind calcium. Northern blot data show that this gene is expressed as
a single 8000 nt transcript and is present in the hepatopancreas of secondary-vitellogenic
females. Primary vitellogenic and other tissues examined in male and female animals
were negative. In sexually plastic intersex animals, removal of the androgenic gland
results in vitellogenin transcription, indicating that the gene is negatively regulated
by the androgenic gland.