Figure 3. Enhancement and suppression of Ubx and Abd-B phenotypes by elongation factor mutants.

The dominant Ubx¹ allele (B) which shows partial haltere to wing transformation [(slightly large halteres and presence of ectopic wing like britstle at the base of stalk (arrow) when compared to wt haltere (A)] was used for enhancement-suppression assay against the elongation mutants. In (C) Elo-A and (D) Cdk9 backgrounds the haltere to wing transformation was enhanced in 100% of transheterozygotes (as can be seen by increase in size and number of wing-like bristles in the haltere). The haltere to wing phenotype was partially suppressed in 100% of the transheterozygotes in (E) Spt4 background (as loss of prominent wing-like bristle along the leading edge of haltere occurs). To investigate if the elongation factors act together to control Ubx gene transcription a triple mutant fly was generated Cdk9/+; Elo-A/Ubx (F) and severe haltere to wing transformation (increased wing-like bristles and overall size of haltere) was observed in 100% of the triple mutants. The haplo-insufficient anteriorization phenotype of partial A7 to A6 (presence of small pigmented segmented below A6, shown by red arrow) and A6 to A5 transformation (presence of bristles in A6 sternite, shown by black arrows) in Abd-B^M1 allele (H compare to G) was used as benchmark for looking for its interaction with the elongation factor mutants. Elongation factors like Elo-A (I), Cdk9 (J), Spt5 (K), Spt4 (L) all enhanced the partial A7 to A6 (increased the small pigmented segment size, shown by red arrows) and A6 to A5 (more bristles in A6 sternite, shown by black arrows) in 100% of the transheterozygotes suggesting its role in facilitating transcription of Abd-B gene. The Nelf-E mutation suppressed the dominant Abd-B phenotype (M compare to G) and made all the transheterozygotes look like wild type files (as seen by loss of A7 to A6 and A6 to A5 transformations) suggesting that it is bringing about negative regulation of Abd-B gene. The triple mutant Cdk9/+; Elo-A/Abd-B^M1 (N) flies show severe enhancement of Abd-B phenotype [which is reflected by increased bristles in A6 sternite (black arrows) and stronger A7 to A6 transformation (red arrow)].