REQUIREMENT OF TEASHIRT (TSH) FUNCTION DURING CELL FATE SPECIFICATIONIN DEVELOPING HEAD STRUCTURES IN DROSOPHILA

The homeotic gene teashirt (tsh) is known to regulate segmental identi ty of the trunk region of the Drosophila embryo. Here we report a requ irement 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 p alps, a phenotype characteristically induced by dominant gain-of-funct ion mutations of Antennapedia (Antp) homeotic gene. Animals transheter ozygous for tsh and Antp mutations displayed an enhanced antenna-to-le g and a striking reduced-eye phenotype suggesting aggravated ANTP mise xpression in eye-antennal discs of these animals. In agreement with th is, in the developing eye-antennal discs of the tsh mutant animals a s ignificant amount of ANTP protein was detected overlapping the domains where tsh is normally expressed. These results suggest that tsh speci fies adult head segments by repressing Antp expression.