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PLoS Genet:光周期诱导开花时间调控取得新进展

  1. PLoS Genetics
  2. 光周期
  3. 开花时间

来源:中国科学院上海生命科学研究院 2013-10-15 14:12

10月10日,植生生态所刘宏涛组在PLoS Genetics杂志发表题为“Multiple bHLH Proteins form Heterodimers to Mediate CRY2-Dependent Regulation of Flowering-Time in Arabidopsis”的研究论文,本文揭示了光周期诱导开花时间中开花素基因FT的转录调控新机制。

10月10日,植生生态所刘宏涛组在PLoS Genetics杂志发表题为“Multiple bHLH Proteins form Heterodimers to Mediate CRY2-Dependent Regulation of Flowering-Time in Arabidopsis”的研究论文,本文揭示了光周期诱导开花时间中开花素基因FT的转录调控新机制。

植物能否成功地进行有性繁殖取决于精确的开花时间。因此,开花时间的调节对农业生产至关重要。作物的地理分布主要取决于光周期调控的开花时间差异。蓝光受体CRY(Cryptochrome)及其结合蛋白CIB1 对于光周期诱导开花至关重要。CRY2以蓝光依赖的形式与转录因子CIB1结合,从而促进开花素基因FT的转录及开花时间。

刘宏涛研究组的研究发现几个CIB1同源的bHLH蛋白与CIB1共同调节开花启始--CIB1,CIB2,CIB4,CIB5都作为激活子直接促进FT的转录。它们在体外都与G-box序列有强亲和力,当把G-box突变为E-box后亲和力极低,但在植物体内它们都可以直接结合到FT的启动子上促进FT的转录,尽管FT启动子中只含有E-box序列。多种体内和体外实验表明这几个不同的bHLH蛋白可以形成异源二聚体,而异源二聚体对E-box有很强的亲和力,说明异源二聚体的形成改变了这些转录因子在体内的DNA结合能力,进而很好的解释了CIB1在体内结合E-box,但在体外却只结合G-box。这是植物中第一次报道bHLH转录因子通过形成异源二聚体而改变DNA结合的亲和力或特异性。

该研究得到了国家自然科学基金委员会和中国科学院等项目的资助。(植生生态所)(生物谷Bioon.com)

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PLoS Genetics
   doi:10.1371/journal.pgen.1003861

Multiple bHLH Proteins form Heterodimers to Mediate CRY2-Dependent Regulation of Flowering-Time in Arabidopsis

 Yawen Liu , Xu Li equal contributor,Kunwu Li,Hongtao Liu mail, Chentao Lin  

Arabidopsis thaliana cryptochrome 2 (CRY2) mediates light control of flowering time. CIB1 (CRY2-interacting bHLH 1) specifically interacts with CRY2 in response to blue light to activate the transcription of FT (Flowering Locus T). In vitro, CIB1 binds to the canonical E-box (CACGTG, also referred to as G-box) with much higher affinity than its interaction with non-canonical E-box (CANNTG) DNA sequences. However, in vivo, CIB1 binds to the chromatin region of the FT promoter, which only contains the non-canonical E-box sequences. Here, we show that CRY2 also interacts with at least CIB5, in response to blue light, but not in darkness or in response to other wavelengths of light. Our genetic analysis demonstrates that CIB1, CIB2, CIB4, and CIB5 act redundantly to activate the transcription of FT and that they are positive regulators of CRY2 mediated flowering. More importantly, CIB1 and other CIBs proteins form heterodimers, and some of the heterodimers have a higher binding affinity than the CIB homodimers to the non-canonical E-box in the in vitro DNA-binding assays. This result explains why in vitro CIB1 and other CIBs bind to the canonical E-box (G-box) with a higher affinity, whereas they are all associated with the non-canonical E-boxes at the FT promoter in vivo. Consistent with the hypothesis that different CIB proteins play similar roles in the CRY2-midiated blue light signaling, the expression of CIB proteins is regulated specifically by blue light. Our study demonstrates that CIBs function redundantly in regulating CRY2-dependent flowering, and that different CIBs form heterodimers to interact with the non-canonical E-box DNA in vivo.

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