Functional characterization of two paralogous JH receptors, methoprene-tolerant 1 and 2, in the silkworm, Bombyx mori (Lepidoptera: Bombycidae)
Functional characterization of two paralogous JH receptors, methoprene-tolerant 1 and 2, in the silkworm, Bombyx mori (Lepidoptera: Bombycidae)
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DOI：
10.1007/s13355-015-0345-8
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发表时间：
2015-08-01
影响因子：
1.3
通讯作者：
Shinoda, Tetsuro
中科院分区：
文献类型：
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作者：
Kayukawa, Takumi;Shinoda, Tetsuro
耐甲虫酯 (Met) 是一种 bHLH-PAS 转录因子，是昆虫保幼激素 (JH) 受体的核心成分。家蚕 Bombyx mori (L.) 的基因组编码两种 Met 旁系同源物：BmMet1 和 BmMet2。我们之前提出，在 JH 存在的情况下，BmMet2 与类固醇受体共激活剂 (BmSRC) 形成功能复合物，并诱导 Kruppel 同源物 1 (BmKr-h1)。在本研究中，我们表征了 BmMet2 结构域并检查了 BmMet1 的作用。对 BmMet2 的一系列报告基因和双杂交检测表明，bHLH 结构域在与 BmKr-h1 (kJHRE) 的 JH 响应元件、转录激活中的 PAS-A 以及 JH 识别中的 PAS-B 的结合中发挥着关键作用。此外，我们确认 BmMet2/BmSRC 复合物识别核心 kJHRE (GGCCTCCACGTG)。发现 BmMet1 与 BmSRC 相互作用，并以 JH 依赖性方式弱激活 kJHRE 报告基因。幼虫和蛹阶段表皮中BmMet1转录水平远高于BmMet2转录水平。相比之下，BmMet2 转录本在幼虫阶段几乎检测不到，但在成虫阶段却很丰富。这些结果表明，BmMet1 参与幼虫中 BmKr-h1 的 JH 依赖性诱导，而 BmMet2 参与成虫中。
Methoprene-tolerant (Met) is a bHLH-PAS transcription factor that functions as a core component of juvenile hormone (JH) receptors in insects. The genome of the silkworm, Bombyx mori (L.), encodes two Met paralogs, BmMet1 and BmMet2. We have previously proposed that BmMet2 forms a functional complex with steroid receptor co-activator (BmSRC) in the presence of JH and induces Kruppel-homolog 1 (BmKr-h1). In this study, we characterized BmMet2 domains and examined the role of BmMet1. A series of reporter and two-hybrid assays on BmMet2 revealed that the bHLH domain played a critical role in the binding to the JH response element of BmKr-h1 (kJHRE), the PAS-A in the transcriptional activation, and the PAS-B in the JH recognition. Furthermore, we confirmed that the BmMet2/BmSRC complex recognizes the core kJHRE (GGCCTCCACGTG). BmMet1 was found to interact with BmSRC and weakly activated the kJHRE reporter in a JH-dependent manner. The BmMet1 transcript level was much higher than the BmMet2 transcript level in the epidermis during the larval and pupal stages. By contrast, the BmMet2 transcript was hardly detected during the larval stage, but was abundant in the adult stage. These results suggest that BmMet1 is involved in the JH-dependent induction of BmKr-h1 in larvae, whereas BmMet2 is involved in adults.