Sd. Weatherbee et al., ULTRABITHORAX REGULATES GENES AT SEVERAL LEVELS OF THE WING-PATTERNING HIERARCHY TO SHAPE THE DEVELOPMENT OF THE DROSOPHILA HALTERE, Genes & development, 12(10), 1998, pp. 1474-1482
Arthropods and vertebrates are constructed of many serially homologous
structures whose individual patterns are regulated by Hox genes. The
Hox-regulated target genes and developmental pathways that determine t
he morphological differences between any homologous structures are not
known. The differentiation of the Drosophila haltere from the wing th
rough the action of the Ultrabithorax (Ubx) gene is a classic example
of Hox regulation of serial homology, although no Ubx-regulated genes
in the haltere have been identified previously. Here, we show that Ubx
represses the expression of the Wingless (Wg) signaling protein and a
subset of Wg- and Decapentaplegic-activated genes such as spalt-relat
ed, vestigial, Serum Response Factor, and achaete-scute, whose product
s regulate morphological features that differ between the wing and hal
tere. In addition, we found that some genes in the same developmental
pathway are independently regulated by Ubx. Our results suggest that U
bx, and Hox genes in general, independently and selectively regulate g
enes that act at many levels of regulatory hierarchies to shape the di
fferential development of serially homologous structures.