nubbin encodes a POU-domain protein required for proximal-distal patterning in the Drosophila wing

Abstract

The nubbin gene is required for normal growth and patterning of the wing in Drosophila. We report here that nubbin encodes a member of the POU family of transcription factors. Regulatory mutants which selectively remove nubbin expression from wing imaginal discs lead to loss of wing structures. Although nubbin is expressed throughout the wing primordium, analysis of genetic mosaics suggests a localized requirement for nubbin activity in the wing hinge. These observations suggest the existence of a novel proximal-distal growth control center in the wing hinge, which is required in addition to the well characterized anterior-posterior and dorsal-ventral compartment boundary organizing centers.

A promoter-proximal silencer modifies the activity of a shared enhancer to mediate divergent expression of nub and pdm2 paralogs in wing development

“…These results suggest that the phenotype associated with the nub 1 allele is due to loss of expression of both nub and pdm2 during wing development. To further establish that nub -associated wing phenotypes are associated with loss of both paralogs, we examined protein levels in wing discs of a different allele that causes a strong wing phenotype, nub 2 (Ng et al, 1995). Consistent with the nub 1 result, nub 2 wing discs show a similar loss of Nub and Pdm2 (Figure S4B).…”

“…Furthermore, wing imaginal discs from pdm2 E46 larvae lack staining by Pdm2-specific antibody (Figure S2A). When nub is mosaically removed in wings that also lack pdm2 the adult appendage shows defects similar to wings containing clones of cells with classical nub regulatory alleles, characterized by reduction of hinge organization, overall wing size, and ectopic margin bristles in the interior blade region (Figure 1E, (Cifuentes & García-Bellido, 1997;Ng et al, 1995). The mosaic phenotype in this background is a result of incomplete knockout from the CRISPR targeting, which can be visualized from clonal loss of Nub protein in the wing disc (Figure S2B).…”

“…The nub 1 allele has previously been shown to have an insertion of the 412 transposon into the promoter of one of two nub isoforms (Ng et al, 1995). However, this insertion is unlikely to explain the loss of expression of both paralogs.…”

“…nub and pdm2 arose in an ancient duplication near the base of the divergence of the Brachycera suborder around 200 million years ago (Figure 1A). Both genes encode similar POU-type homeodomain transcription factors (TFs) (Figure S1) and play a role in development of a wide variety of cell types (Cifuentes & García-Bellido, 1997; Corty et al, 2016; Ng et al, 1995; Yeo et al, 1995). In winged insects (Pterygota) nub is a conserved marker for wings and has been shown to be essential for wing development from beetles to flies (Averof & Cohen, 1997; Cifuentes & García-Bellido, 1997; Ng et al, 1995; Tomoyasu et al, 2009).…”

Out from under the wing: reconceptualizing the insect wing gene regulatory network as a versatile, general module for body-wall lobes in arthropods

“…We chose a set of ten genes to investigate, based on the involvement of their orthologues in thoracic body-wall or wing development in the developmental genetic model organisms Drosophila melanogaster (figure 1b) and Tribolium castaneum. We chose three of these genes-apterous (ap) [23], vestigial (vg) [24] and nubbin (nub) [25,26]-because they have been a focus of the wing serial homology debate [27][28][29][30]. Six additional genes were selected because of their interactions with these during body-wall or wing patterning: homothorax (hth) [31], araucan/ caupolican (ara/caup) [32], mirror (mirr) [33], tiptop/teashirt (tio) [34], tailup (tup) [35] and u-shaped (ush) [36,37].…”