Subcellular sites of the signal transduction and degradation of phytochrome A.
Subcellular sites of the signal transduction and degradation of phytochrome A.
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DOI：
10.1093/pcp/pcq121
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发表时间：
2010-10
影响因子：
4.9
通讯作者：
Gabriela Toledo‐Ortiz;Y. Kiryu;Junko Kobayashi;Yoshito Oka;Yumi Kim;H. Nam;N. Mochizuki;A. Nagatani-A.
中科院分区：
文献类型：
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作者：
Gabriela Toledo‐Ortiz;Y. Kiryu;Junko Kobayashi;Yoshito Oka;Yumi Kim;H. Nam;N. Mochizuki;A. Nagatani-A.
光敏色素在植物的整个生命周期中调节着各种生理和发育过程。在光敏色素家族的成员中，光敏色素A（phyA）专门介导由连续远红光引起的远红光高辐照度响应（FR-HIR）。在FR-HIR，核积累的phyA，这之前的生理反应，提出了所需的响应。与FR相反，红光诱导phyA的快速降解以抑制phyA的不期望的长期光形态发生响应。在本研究中，我们比较了phyA衍生物的生物活性，无论是核定位（NLS）或出口（内斯）信号序列连接。这些衍生物在拟南芥phyA突变体中的PHYA启动子的控制下表达。详细的显微镜观察显示，没有信号序列的phyA-绿色荧光蛋白（GFP）仅定位在黑暗中的细胞质中。在暴露于红光和远红光后观察到快速核进入。有趣的是，phyA-GFP-NLS和phyA-GFP-内斯在连续红光下均迅速降解。此外，蛋白酶体抑制剂在这两种条件下同样延迟降解。因此，phyA降解的类似机制可能存在于细胞质和细胞核中。正如先前报道所预期的，phyA-GFP-NLS而非phyA-GFP-内斯介导FR-HIR的不同方面，例如抑制下胚轴伸长和快速诱导基因表达，证实了phyA核定位是FR-HIR所需的。此外，phyA-GFP和phyA-GFP-NLS反应的详细时程分析显示，它们几乎无法区分，这提出了phyA细胞质在黑暗中保留的生理相关性的问题。
Phytochrome regulates various physiological and developmental processes throughout the life cycle of plants. Among the members of the phytochrome family, phytochrome A (phyA) exclusively mediates the far-red light high irradiance response (FR-HIR), which is elicited by continuous far-red light. In FR-HIR, nuclear accumulation of phyA, which precedes physiological responses, is proposed to be required for the response. In contrast to FR, red light induces rapid degradation of phyA to suppress undesirable long-term photomorphogenic responses of phyA. In the present study, we compared biological activities between phyA derivatives to which either a nuclear localization (NLS) or export (NES) signal sequence was attached. Those derivatives were expressed under the control of the PHYA promoter in the Arabidopsis phyA mutant. Detailed microscopic observation revealed that the phyA-green fluorescent protein (GFP) without a signal sequence is localized exclusively in the cytoplasm in darkness. Rapid nuclear entry was observed after exposure to both red and far-red light. Interestingly, both phyA-GFP-NLS and phyA-GFP-NES were rapidly degraded under continuous red light. Furthermore, a proteasome inhibitor delayed degradation equally under these two conditions. Therefore, similar mechanisms for phyA degradation may exist in the cytoplasm and nucleus. As expected from previous reports, phyA-GFP-NLS, but not phyA-GFP-NES, mediated different aspects of FR-HIR, such as inhibition of hypocotyl elongation and rapid induction of gene expression, confirming that phyA nuclear localization is required for FR-HIR. In addition, a detailed time course analysis of phyA-GFP and phyA-GFP-NLS responses revealed that they were almost indistinguishable, raising the question of the physiological relevance of phyA cytoplasmic retention in darkness.