Redundant ecdysis regulatory functions of three nuclear receptor HR3 isoforms in the direct-developing insect Blattella germanica
Redundant ecdysis regulatory functions of three nuclear receptor HR3 isoforms in the direct-developing insect Blattella germanica
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DOI：
10.1016/j.mod.2006.12.003
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发表时间：
2007-03-01
影响因子：
2.6
通讯作者：
Belles, Xavier
中科院分区：
文献类型：
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作者：
Cruz, Josefa;Martin, David;Belles, Xavier
在半变态昆虫中，20-羟基乙酮（20 E）触发的遗传等级的分子基础实际上是未知的。在蟑螂德国小蠊，我们以前的特点是蜕皮激素受体，BgEcR-A的一种亚型，其异二聚体的合作伙伴，BgRXR-S和BgRAR-L的两种亚型。20 E触发的遗传等级中的早-晚基因之一是HR 3。本文报道了在B中发现的三种HR 3亚型。BgHR 3-A、BgHR 3-B和BgHR 3-B2在前胸腺、表皮和脂肪体中的表达研究表明，这三种异构体的表达与若虫各龄期循环蜕皮甾体的表达高峰相一致。用脂肪体组织进行的体外实验表明，20 E诱导BgHR 3亚型的表达，并且与20 E和蛋白抑制剂放线菌酮孵育不抑制诱导，这表明20 E对BgHR 3活化的作用是直接的。这已经通过BgEcR-A的体内RNAi进一步证实，其已经显示该核受体是完全激活BgHR 3的表达所需的。RNAi也被用于证实BgHR 3在蜕皮中的功能。具有沉默的BgHR 3的若虫完成了脱膜，但不能蜕皮（它们复制并叠加了口部、下咽部、气管系统和角质层）。这表明BgHR 3直接参与蜕皮。最后，特定亚型的RNA干扰表明它们在功能上是冗余的，至少在蜕皮过程中是这样。(c)2007爱思唯尔爱尔兰有限公司保留所有权利。
In hemimetabolous insects, the molecular basis of the 20-hydroxyeedysone (20E)-triggered genetic hierarchy is practically unknown. In the cockroach Blattella germanica, we had previously characterized one isoform of the ecdysone receptor, BgEcR-A, and two isoforms of its heterodimeric partner, BgRXR-S and BgRAR-L. One of the early-late genes of the 20E-triggered genetic hierarchy, is HR3. In the present paper, we report the discovery of three isoforms of HR3 in B. germanica, that were named BgHR3-A, BgHR3-B, and BgHR3-B2Expression studies in prothoracic gland, epidermis and fat body indicate that the expression of the three isoforms coincides with the peak of circulating ecdysteroids at each nymphal instar. Experiments in vitro with fat body tissue have shown that 20E induces the expression of BgHR3 isoforms, and that incubation with 20E and the protein inhibitor cycloheximide does not inhibit the induction, which indicates that the effect of 20E on BgHR3 activation is direct. This has been further confirmed by RNAi in vivo of BgEcR-A, which has shown that this nuclear receptor is required to fully activate the expression of BgHR3. RNAi has been also used to demonstrate the functions of BgHR3 in ecdysis. Nymphs with silenced BgHR3 completed the apolysis but were unable to ecdyse (they had duplicated and superimposed the mouth parts, the hypopharinge, the tracheal system and the cuticle layers). This indicates that BgHR3 is directly involved in ecdysis. Finally, RNAi of specific isoforms has showed that they are functionally redundant, at least regarding the ecdysis process. (c) 2007 Elsevier Ireland Ltd. All rights reserved.