Yolk polypeptide gene expression in cultured Drosophila cells

The role of 20-hydroxyecdysone on the control of spider vitellogenesis

We investigated the role of 20-hydroxyecdysone (20E) on the ovarian maturation and protein levels and pattern in adult females of the spider Tegenaria atrica. In unmated females, the ovaries did not initiate vitellogenesis and levels of proteins in the hemolymph and ovaries were low. Unmated females treated with 20E showed an increase in the total amount of proteins in their hemolymph and ovaries, comparable with that in untreated mated females. Vitellogenesis was observable histologically in 20E treated unmated females as in untreated mated ones. The electrophoretic analysis of total proteins revealed a 47 kDa band expressed in the vitellogenic ovaries and hemolymph of 20E treated unmated females and untreated mated ones as in newly laid eggs. We hypothesize that this 47 kDa protein could belong to the vitellogenin-vitellin complex. We describe in this paper, for the first time in a spider, the partial characterization of putative yolk protein.

The juvenile hormone analogue, methoprene, inhibits ecdysterone induction of small heat shock protein gene expression

The small heat shock protein (hsp) genes of Drosophila are expressed in cultured cells in response to the moulting hormone, ecdysterone. We show here that juvenile hormone (JHIII) and the juvenile hormone analogue, methoprene, inhibit that induction in a dose-dependent manner. Heat shock induction is not inhibited. In transient expression studies using S3 line cells transfected with EcRE-CAT constructs, methoprene inhibition was found to require a 2-hr pretreatment (before ecdysterone addition), and methoprene's continued presence was essential. Farnesol, farnesyl acetate, and retinoic acid did not cause inhibition. Several models of methoprene inhibition are discussed.

Differential translatability of antifreeze protein mRNAs in a transgenic host

The expression of fusion gene constructs containing Drosophila regulatory sequences and the structural portions of fish antifreeze protein genes have been examined by transfer into Drosophila melanogaster using P elements. A fusion gene, containing the enhancer, promoter, and cap site of the yolk polypeptide 1 gene, joined in the 5'-untranslated region to the structural portion of the winter flounder type I antifreeze gene, was transcribed in mature female transformants to give an mRNA of the predicted size, but no antifreeze protein was detected by Western blotting. When the same antifreeze protein gene was fused to a Drosophila hsp 70 gene regulatory region and placed downstream of the yolk polypeptide gene enhancer, appropriate expression of mRNA was directed by both gene regulatory elements. However, a translation product from this mRNA was only observed under heat shock conditions and was present at low levels. It is suggested that type I antifreeze mRNA, with its high content of alanine codons and their grouping into clusters of up to seven in a row, is poorly translated when in competition with other host mRNAs. In agreement with this hypothesis, a fusion gene construct between the yolk protein gene regulatory region and two type III antifreeze protein genes produced sub-mmolar concentrations of antifreeze protein in mature females from each of several transgenic lines analysed. The type III antifreeze protein does not have an imbalanced amino acid composition or sequence irregularities, and may be an appropriate choice for conferring freeze protection to frost-susceptible hosts by gene transfer.