Abstract
Regulation of developmental gene expression in eukaryotes involves several levels. One of them is the maintenance of gene expression along the life of the animal once it is started by different triggers early in development. One of the questions in the field is when in developmental time, the animal start to use the different maintenance mechanisms. The trithorax group (TrxG) of genes was first characterized as essential for maintaining homeotic gene expression. The TrxG gene tonalli interacts genetically and physically with genes and subunits of the BRAHMA BAP chromatin remodeling complex and encodes TnaA proteins with putative E3 SUMO-ligase activity. In contrast to the phenocritic lethal phase of animals with mutations in other TrxG genes, tna mutant individuals die late in development. In this study we determined the requirements of TnaA for survival at pupal and adult stages, in different tna mutant genotypes where we corroborate the lack of TnaA proteins, and the presence of adult homeotic loss-of-function phenotypes. We also investigated whether the absence of TnaA in haltere and leg larval imaginal discs affects the presence of the homeotic proteins Ultrabithorax and Sex combs reduced respectively by using some of the characterized genotypes and more finely by generating TnaA defective clones induced at different stages of development. We found that, tna is not required for growth or survival of imaginal disc cells and that it is a fine modulator of homeotic gene expression.
Highlights
Homeotic (Hox) genes determine the segmental identity in Drosophila
In this work we explored TnaA requirements for the expression of the Hox genes Ultrabithorax (Ubx) and Sex combs reduced (Scr), through immunostaining of the respective Hox proteins in imaginal discs of late third instar larvae with mutant tna genotypes, or in TnaA defective clones generated at different stages of development
In this work we studied the role of the trithorax group (TrxG) gene tna on Hox gene expression in larval imaginal discs
Summary
Homeotic (Hox) genes determine the segmental identity in Drosophila. In Drosophila Hox genes are in two complexes, the bithorax (BX-C) and the Antennapedia (ANTP-C) complexes. As tna was identified as a brm-modifier gene and animals with tna mutant combinations reach the pharate stage and die before reaching adulthood presenting Hox loss-offunction phenotypes [5], one hypothesis is that its function is required to maintain Hox gene expression by facilitating chromatin remodeling by the BRAHMA BAP complex at these late stages of development. These facts make TnaA protein(s) interesting to study for the function they could have to ensure correct gene expression at these stages of development. That TnaA finely modulates Hox gene expression in imaginal cells and that its function can only be observed when Hox gene expression is not robustly regulated
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