Interactors of iab-7 cis- regulatory domain of the Bithorax complex. V.S. Chopra , R.K. Mishra. CCMB, Hyderabad, Andhra Pradesh, India.

   The Bithorax complex (BX-C) of Drosophila melanogaster has three homeotic genes, Ubx,abd-A,Abd-b.The cis- regulatory domains present within the complex in a collinear fashion control the spatial expression pattern of these genes,along the anterior-posterior body axis.These regulatory elements are believed to function via higher order chromatin organization. Deletions of such elements and analysis of a large number of other mutations suggest that the cis-regulatory domains are functionally independent.For instance, the loss of function of iab-7 cis-regulatory element affects primarily A7, as seen by a homeotic transformation of A7 to A6.
   Using weak iab-7 alleles, we did a screen to look for interactors of iab-7 out side the complex using two phenotypic criteria, viz., homeotic transformation of A7 and rotation of male genitalia. These strategies led to the identification of several trx-g and Pc-G mutations as the interactors of iab-7. Interestingly, however, different mutations showed very different kinds of interactions. We then used P element insertion lines containing lac Z reporter gene within iab-7domain to test how different mutations, identified in the experiments mentioned above, influence the expression of the lac Z at different stages of development.
   Based on the result of these two sets of experiments, we can subdivide trx-G and Pc-G genes into three categories: the genes that affect primarily iab-7, the ones that showed more general effect and rest showing no interaction. We have now started, based on these observations, testing interactions among these categories of genes in wt and iab-7 background.