D'Avino P P, Crispi S, Polito L C, Furia M
Dipartimento di Genetica, Biologia Generale e Molecolare, Università di Napoli, Italy.
Mech Dev. 1995 Feb;49(3):161-71. doi: 10.1016/0925-4773(94)00313-c.
During the third larval instar, the steroid moulting hormone ecdysone activates three temporally distinct puff sets on the D. melanogaster salivary gland polytene chromosome: the so-called intermoult, early and late puffs. Hormonal regulation of intermoult puffs is quite complex and, so far, largely not understood. In order to further investigate this aspect, we have analysed the effects of mutations in a key regulator of the ecdysone response at the onset of metamorphosis, the Broad-Complex (BR-C) locus, on the expression of genes mapping at the 3C intermoult puff. On the basis of an accurate examination of 3C intermoult gene activity in single, carefully staged, third instar larvae of wild-type and BR-C mutant strains, we were able to subdivide these genes into two groups. Each group is characterised by a different temporal expression profile, so that at the beginning of the wandering stage the transcription of the first group declines as group II transcription is induced. Interestingly, the BR-C locus appears to play a regulatory role in establishing this transcriptional switch. By using mutants of each of the three lethal complementation groups, we precisely defined the role of BR-C functions in this developmental transition and we show that this locus also plays an essential role in the early pre-metamorphic hormonal response.
在幼虫第三龄期，类固醇蜕皮激素蜕皮甾酮激活了黑腹果蝇唾液腺多线染色体上三组在时间上不同的胀泡：即所谓的蜕皮间期、早期和晚期胀泡。蜕皮间期胀泡的激素调节相当复杂，到目前为止，在很大程度上还不清楚。为了进一步研究这一方面，我们分析了变态开始时蜕皮甾酮反应的关键调节因子——宽复合体（BR-C）基因座的突变对位于3C蜕皮间期胀泡处基因表达的影响。基于对野生型和BR-C突变体菌株单只、精心分期的第三龄幼虫中3C蜕皮间期基因活性的精确检测，我们能够将这些基因分为两组。每组的特征是不同的时间表达模式，因此在化蛹前期开始时，第一组基因的转录下降，同时第二组基因的转录被诱导。有趣的是，BR-C基因座似乎在建立这种转录开关中起调节作用。通过使用三个致死互补群中每一个的突变体，我们精确地确定了BR-C功能在这一发育转变中的作用，并且我们表明该基因座在变态前早期的激素反应中也起着至关重要的作用。
