20-Hydroxyecdysone, but Not Juvenile Hormone, Regulation ofyolk proteinGene Expression Can Be Mapped tocis-Acting DNA Sequences

Abstract

The three yolk protein genes (yps) of Drosophila melanogaster are expressed in the ovary and fat body of the adult female. Their levels of expression in the fat body depend upon both juvenile hormone (JH) and 20-hydroxyecdysone (20E). Using transformed lines of flies with various flanking sequences from the yp genes and lacZ, Adh, or native yp genes as reporters, the regulation of the three yp genes by 20E and the JH analogue ZR515 (methoprene) was investigated. For 20E, induction of reporter gene expression in males was assayed and, for JH, upregulation of the genes in nutritionally deprived females, which express yolk proteins (YPs) at very low levels, was followed. We were able to map 20E inducible sites upstream of yp3 and sites located 3' and within the coding sequence or introns of yp3 which can interact to respond to 20E. There are also sites in the intergenic spacer between yp1 and yp2. Evidence for repressors was also found upstream of the yp genes, suggesting downstream 20E inducible elements may be important in vivo. There appears to be a difference in the response to 20E in the fat body of the thorax and abdomen between different constructs in males. It is not clear whether those sequences which respond to 20E are genuine ecdysone response elements (i.e., binding sites for the ecdysone receptor) or if the effect is indirect. Methoprene upregulation of YPs, however, was only ever observed using native yp genes as reporters, suggesting that this hormone may act on intron sequences or yp coding sequences, or perhaps by influencing stability of the yp mRNA.

Posttranscriptional control of the competence factor βFTZ-F1 by juvenile hormone in the mosquito Aedes aegypti

“…On the other hand, JHs have been documented as activating the transcription of many genes in diverse insects. The extent of most of the inductions has been relatively weak, and genetic analyses of the regulatory regions have failed to yield consensus on the JH response elements (40). Here, our results suggest that JH controls the synthesis of ␤FTZ-F1 protein in A. aegypti.…”

Chitin metabolism in insects: structure, function and regulation of chitin synthases and chitinases

“…The Drosophila genes Eips 28 and Eips 29, for instance, are controlled tissueand stage-specifically by ecdysone-responsive elements present in the upstream and downstream flanking regions (Andres and Cherbas, 1994). Further examples of this mode of ecdysteroid-mediated transcriptional regulation are the Drosophila genes encoding the yolk protein (Bownes et al, 1996), the heat-shock proteins hsp23 and hsp27 (Luo et al, 1991), the caspase DRONC (Dorstyn et al, 1999;Hawkins et al, 2000) and the Manduca genes EcR-A and EcR-B1, which encode two ecdysone receptor (EcR) isoforms (Jindra et al, 1996). Downregulation of transcriptional activities by ecdysteroids was observed too, but these effects may be due to indirect actions.…”

Sex Steroids in Insects and the Role of the Endosymbiont Wolbachia:A New Perspective

“…In adults the role played by ecdysteroids is much less explored: for example, it has been demonstrated that they control several important aspects of reproduction, including ovarian development and oogenesis (Carney & Bender, 2001;Raikhel et al, 2005;Riddifort, 1993;Swevers & Iatrou, 2003). In many insect species 20E is also directly involved in the regulation of vitellogenin biosynthesis by the female fat body, a metabolic tissue functionally analogous to the vertebrate liver, and it can also induce vitellogenin synthesis in males (Bownes et al, 1983;Bownes et al, 1996;Huybrechts & De Loof, 1977;Zhu et al, 2007). The 20E has also been shown to affect sexual behaviour, having a role in courtship initiation by males, and promoting male-male sexual attraction (Ganter et al, 2007).…”