ABSTRACT
The homeotic gene teashirt (tsh) is known to regulate segmental identity of the trunk region of the Drosophila embryo. Here we report a requirement for tsh function in the development of adult head structures. Animals homozygous for a viable tsh allele or heterozygous for various embryonic recessive lethal alleles displayed miniaturized maxillary palps, a phenotype characteristically induced by dominant gain-of-function mutations of Antennapedia (Antp) homeotic gene. Animals transheterozygous for tsh and Antp mutations displayed an enhanced antenna-to-leg and a striking reduced-eye phenotype suggesting aggravated ANTP misexpression in eye-antennal discs of these animals. In agreement with this, in the developing eye-antennal discs of the tsh mutant animals a significant amount of ANTP protein was detected overlapping the domains where tsh is normally expressed. These results suggest that tsh specifies adult head segments by repressing Antp expression.
ABSTRACT
Developmental expression of transduced mini-white(w) gene of Drosophila is sensitive to its flanking genomic enhancers. Taking advantage of this phenomenon, we mobilized a P lacW transposon and screened for new transposant lines which showed patterned expression of the mini-w gene in adult eyes. From a screen of about 1,000 independent P lacW transposant lines on the second chromosome, we identified 7 lines which showed patterned w expression in adult eyes. These P insertions were assigned to engrailed, wingless and teashirt genes based on their chromosomal locations, developmental expression of the lacZ reporter gene, lethal embryonic mutant phenotypes and, finally, their failure to complement the lethal alleles of the respective genetic loci. Our results show that although only a small fraction of the total transposant lines displayed patterned w expression, the genetic loci thus identified are those which play essential roles in pattern formation. Scopes of screens for genetic loci based on w reporter gene expression in adult eyes are discussed.
