Little J W, Byrd C A, Brower D L
Department of Biochemistry, University of Arizona, Tucson 85721.
Genetics. 1990 Apr;124(4):899-908. doi: 10.1093/genetics/124.4.899.
We have examined the patterns of expression of the homeotic gene Ubx in imaginal discs of Drosophila larvae carrying mutations in the abx, bx and pbx regulatory domains. In haltere discs, all five bx insertion mutations examined led to a general reduction in Ubx expression in the anterior compartment; for a given allele, the strength of the adult cuticle phenotype correlated with the degree of Ubx reduction. Deletions mapping near or overlapping the sites of bx insertions, including three abx alleles and the bx34e-prv(bx-prv) allele, showed greatly reduced Ubx expression in parts of the anterior compartment of the haltere disc; however, anterior patches of strong Ubx expression often remained, in highly variable patterns. As expected, the pbx1 mutation led to reduced Ubx expression in the posterior compartment of the haltere disc; surprisingly, pbx1 also led to altered expression of the en protein near the compartment border in the central region of the disc. In the metathoracic leg, all the bx alleles caused extreme reduction in Ubx expression in the anterior regions, with no allele-specific differences. In contrast, abx and bx-prv alleles resulted in patchy anterior reductions in third leg discs. In the larval central nervous system, abx but not bx alleles affected Ubx expression; the bx-prv deletion gave a wild-type phenotype, but it could not fully complement abx mutations. In the posterior wing disc, the bx-prv allele, and to a much lesser extent the bx34e chromosome from which it arose, led to ectopic expression of Ubx. Unlike other grain-of-function mutations in the BX-C, this phenotype appeared to be partially recessive to wild type. Finally, we asked whether the ppx transformation, which results from early lack of Ubx+ function in the mesothorax and is seen in abx animals, is due to ectopic Scr expression. Some mesothoracic leg and wing discs from abx2 larvae displayed ectopic expression of Scr, which was variable in extent but always confined to the posterior compartment.
我们研究了同源异型基因Ubx在果蝇幼虫成虫盘（imaginal discs）中的表达模式，这些幼虫在abx、bx和pbx调控结构域携带突变。在平衡棒（haltere）盘中，所检测的全部5个bx插入突变均导致前区室中Ubx表达普遍降低；对于给定的等位基因，成虫表皮表型的强度与Ubx降低的程度相关。定位在bx插入位点附近或与其重叠的缺失，包括3个abx等位基因和bx34e - prv（bx - prv）等位基因，显示平衡棒盘中前区室部分区域的Ubx表达大幅降低；然而，前区室中强Ubx表达的斑块通常仍然存在，且模式高度可变。正如预期那样，pbx1突变导致平衡棒盘后区室中Ubx表达降低；令人惊讶的是，pbx1还导致盘中央区域区室边界附近的en蛋白表达改变。在中胸腿中，所有bx等位基因均导致前区Ubx表达极度降低，且无等位基因特异性差异。相比之下，abx和bx - prv等位基因导致第三腿盘中前区出现斑驳的表达降低。在幼虫中枢神经系统中，abx等位基因而非bx等位基因影响Ubx表达；bx - prv缺失呈现野生型表型，但它不能完全互补abx突变。在后翅盘中，bx - prv等位基因以及产生它的bx34e染色体在小得多的程度上，导致Ubx异位表达。与BX - C中的其他功能获得性突变不同，这种表型似乎对野生型部分隐性。最后，我们探究了ppx转化（其源于中胸早期缺乏Ubx + 功能且在abx动物中可见）是否是由于Scr异位表达所致。来自abx2幼虫的一些中胸腿和翅盘显示Scr异位表达，其程度可变但总是局限于后区室。
