Juvenile hormone prevents ecdysteroid-induced expression of broad complex RNAs in the epidermis of the tobacco hornworm, Manduca sexta.
Juvenile hormone prevents ecdysteroid-induced expression of broad complex RNAs in the epidermis of the tobacco hornworm, Manduca sexta.
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DOI：
10.1006/dbio.1998.9059
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发表时间：
1998-11
影响因子：
2.7
通讯作者：
Baohua Zhou;K. Hiruma;T. Shinoda;L. Riddiford
中科院分区：
文献类型：
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作者：
Baohua Zhou;K. Hiruma;T. Shinoda;L. Riddiford
从烟草天蛾Manduca sexta中分离出黑腹果蝇Broad Complex（BRC）基因的cDNA同源物，其在N-末端BTB结构域中与果蝇BRC显示出预测的88%氨基酸同一性。通过RT-PCR获得了果蝇Z2，Z3和Z4结构域的三个锌指结构域编码同源物（分别为93%，100%和85%的同一性）。在螳螂背腹表皮中，在幼虫蜕皮期间未观察到BRC RNA。三个BRC成绩单-6.0，7.0，和9.0 KB-第一次出现在第五（最后）龄的喂养阶段结束时，表皮暴露于蜕皮激素在保幼激素（JH）的情况下，并成为致力于蛹分化。这些RNA诱导在第2天第五幼虫表皮在体外由20-羟基蜕皮激素（20 E）在没有JH的剂量反应和时间过程类似的诱导蛹承诺。这种诱导20 E在体外被阻止的JH I在体内看到的幼虫蜕皮期间的水平的存在。在翅盘，BRC RNA蜕皮后不久出现的第五龄，正好与这些光盘的变态能力的发病。在第四龄蜕皮期间应用JH类似物吡丙昔芬延迟并降低了在第五龄早期的翼盘中看到的BRC mRNA的水平，但并没有完全阻止它们在该组织中的出现，该组织首先在变态时分化。因此，BRC转录因子的表达似乎是昆虫变态所必需的表皮遗传重编程的第一个分子指标之一。JH如何阻止BRC在表皮中的表达可能为理解这种激素如何控制变态提供了关键。
A cDNA homolog of the Drosophila melanogaster Broad Complex (BRC) gene was isolated from the tobacco hornworm, Manduca sexta, which shows a predicted 88% amino acid identity with Drosophila BRC in the N-terminal BTB domain. Three zinc finger domains encoding homologs of the Drosophila Z2, Z3, and Z4 domains (93, 100, and 85% identity, respectively) were obtained by RT-PCR. In Manduca dorsal abdominal epidermis, BRC RNAs were not observed during the larval molt. Three BRC transcripts-6.0, 7.0, and 9.0 kb-first appeared at the end of the feeding stage of the fifth (final) instar when the epidermis is exposed to ecdysteroids in the absence of juvenile hormone (JH) and becomes committed to pupal differentiation. These RNAs were induced in day 2 fifth larval epidermis in vitro by 20-hydroxyecdysone (20E) in the absence of JH with dose-response and time courses similar to the induction of pupal commitment. This induction by 20E in vitro was prevented by the presence of JH I at levels seen in vivo during the larval molt. In the wing discs, the BRC RNAs appeared shortly after ecdysis to the fifth instar and coincided with the onset of metamorphic competence of these discs. Application of a JH analogue pyriproxifen during the fourth instar molt delayed and reduced the levels of BRC mRNAs seen in the wing discs in the early fifth instar, but did not completely prevent their appearance in this tissue that first differentiates at metamorphosis. The expression of the BRC transcription factors thus appears to be one of the first molecular indications of the genetic reprogramming of the epidermis necessary for insect metamorphosis. How JH prevents BRC expression in this epidermis may provide the key to understanding how this hormone controls metamorphosis.