The pronotum LIM-HD gene tailup is both a positive and a negative regulator of the proneural genes achaete and scute of Drosophila

Abstract

Early in the development of the imaginal wing disc of Drosophila, the LIM-HD gene tailup (islet), together with the HD genes of the iroquois complex, specify the notum territory of the disc. Later, tailup has been shown to act as a prepattern gene that antagonizes formation of sensory bristles on the notum of this fly. It has been proposed that Tailup downregulates the expression of the proneural genes achaete and scute by interfering with factors needed to activate these genes in the dorsocentral and scutellar regions of the disc. By means of a clonal analysis performed with tailup null alleles, here we show that, on the one hand, tailup is necessary to prevent formation of extra macrochaetae on most of the 11 sites where these landmark bristles arise on the fly notum. On the other hand, tailup is required to activate achaete and scute at the dorsocentral region, probably by acting as an hexameric complex with the cofactor Chip and the transcriptional activator Sspd on the dorsocentral enhancer of the achaete-scute complex. In contrast, in the scutellar region Tailup acts downstream of achaete-scute, antagonizing the proneural function of these genes probably in cooperation with Chip. We conclude that tailup acts on bristle development by several, even antagonistic, mechanisms.

Tup/Islet1 integrates time and position to specify muscle identity in Drosophila

“…1A). tup ex4 null embryos (de Navascués and Modolell, 2010) show a DA3 duplication in 78% of segments (n102) (Fig. 1E-EЈ) observed in Df(2L)-Exel7072 and Df(2L)Exel7073 embryos.…”

“…Drosophila mutant and transgenic strains were: tup ex4 (de Navascués and Modolell, 2010), col 1 , rp298-lacZ (Nose et al, 1998), Mhc-GFP (Eric Olson and Elisabeth Chen, Dallas, USA), twistGal4 (Baylies and Bate, 1996), IsletH-GFP, UAS-tup (Thor and Thomas, 1997), N 55e11 (Salzberg et al, 1994), tin EC40 (Bodmer, 1993) and Vg-lacZ (Richard Cripps, Albuquerque, USA). Mutant strains were balanced over marked chromosomes: Cyo wg-lacZ; Cyo dfd-EYFP; TM3 twist-lacZ.…”

The bristle pattern development in Drosophila melanogaster: the prepattern and achaete-scute genes

“…As has been shown, the presence of the TUP protein at the sites for future proneural clusters for the remaining macrochaetes blocks emergence of additional SOP cells within the cluster. Two mechanisms underlying this effect are considered, namely, inhibition of achaetescute expression via the TUP interaction with transcription activators or repression of the ACSC target genes (de Navascués, Modolell, 2010).…”

Chip/Ldb1 interacts with Tailup/islet1 to regulate cardiac gene expression in Drosophila

“…However, unlike the GATA‐type zinc fingers, which bind DNA, the LIM domains act as a protein‐protein interacting platform (reviewed in Bach, ; Hobert & Westphal, ). The function of multiprotein complexes including Tup has been studied so far in the developing nervous system and in prepatterning of the dorsal mesothorax but not in heart development (Biryukova & Heitzler, ; de Navascues & Modolell, ; Thor & Thomas, ; Thor et al, ).…”