Systematic analysis of how phytochrome B dimerization determines its specificity
Systematic analysis of how phytochrome B dimerization determines its specificity
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DOI：
10.1038/nplants.2015.90
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发表时间：
2015-07-06
期刊：
影响因子：
18
通讯作者：
Fleck, Christian
中科院分区：
文献类型：
--
作者：
Klose, Cornelia;Venezia, Filippo;Fleck, Christian
光敏色素是一种红光/远红光探测光感受器，调节植物生长发育。它们在不活跃的Pr（红光吸收）和生理上活跃的Pfr（远红光吸收）形式之间进行光交换，充当光控分子开关。虽然两种主要的植物光敏色素A （phyA）和B （phyB）具有相似的吸收特性，但它们在作用光谱上表现出巨大的差异。由于这两种光敏色素在营养荫凉下拮抗调节幼苗发育，因此植物必须明确区分phyA和phyB的作用。这种区别不能仅仅通过光敏色素的分子性质来理解，而显然是由于光敏色素系统的动力学。利用综合实验和数学建模方法，我们表明光敏色素二聚化是phyB功能的基本要素。我们的研究结果表明，不依赖于光的Pfr到Pr弛豫（暗还原）和与核体的结合/解离（NBs）严重依赖于phyB二聚体的构象状态。我们得出结论，只有phyB的Pfr-Pfr同型二聚体可以触发生理反应，导致phyB在远红色光谱范围内的功能受到抑制。
Phytochromes are red/far-red-light detecting photoreceptors that regulate plant growth and development. They photo-interconvert between an inactive Pr (red-light absorbing) and a physiologically active Pfr (far-red-light absorbing) form, acting as light-controlled molecular switches. Although the two major plant phytochromes A (phyA) and B (phyB) share similar absorption properties, they exhibit dramatic differences in their action spectra. Since both phytochromes antagonistically regulate seedling development under vegetative shade, it is essential for plants to clearly distinguish between phyA and phyB action. This discrimination is not comprehensible solely by the molecular properties of the phytochromes, but is evidently due to the dynamics of the phytochrome system. Using an integrated experimental and mathematical modelling approach we show that phytochrome dimerization is an essential element for phyB function. Our findings reveal that light-independent Pfr to Pr relaxation (dark reversion) and association/dissociation to nuclear bodies (NBs) severely depend on the conformational state of the phyB dimer. We conclude that only Pfr-Pfr homodimers of phyB can be responsible for triggering physiological responses, leading to a suppression of phyB function in the far-red range of the light spectrum.