Functional analysis of a 450-amino acid N-terminal fragment of phytochrome B in Arabidopsis
Functional analysis of a 450-amino acid N-terminal fragment of phytochrome B in Arabidopsis
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DOI：
10.1105/tpc.104.022350
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发表时间：
2004-08-01
期刊：
影响因子：
11.6
通讯作者：
Nagatani, A
中科院分区：
文献类型：
--
作者：
Oka, Y;Matsushita, T;Nagatani, A
光敏色素是植物中的主要光感受器，由两个结构域组成：N 端感光结构域和 C 端结构域。最近，光敏色素 B (phyB) 的 651 个氨基酸的光感应结构域已被证明可充当细胞核中的功能性光感受器。光敏色素 (PHY) 结构域位于光敏结构域的 C 末端，是光敏色素光谱完整性所必需的；然而，人们对该结构域的信号转导活性知之甚少。在这里，我们建立了转基因拟南芥品系，在 phyB 缺陷的背景下表达缺乏 PHY 结构域的 phyB N 端 450 个氨基酸片段 (N450)。对这些植物的分析表明，当连接到短核定位信号和 β-葡萄糖醛酸酶时，N450 可以充当活性光感受器。重组色肽的体外光谱分析进一步表明，与全长 phyB 的 Pfr 形式相比，N450 Pfr 形式（光敏色素的活性形式）的稳定性显着降低。与此一致的是，表达 N450 的植物未能对长时间施加的间歇光做出反应，表明 N450 Pfr 在体内的寿命很短。综上所述，我们的研究结果表明，PHY 域对于 phyB 信号转导来说是可有可无的，但对于稳定 phyB 的 Pfr 形式是必需的。
Phytochrome, a major photoreceptor in plants, consists of two domains: the N-terminal photosensory domain and the C-terminal domain. Recently, the 651-amino acid photosensory domain of phytochrome B (phyB) has been shown to act as a functional photoreceptor in the nucleus. The phytochrome (PHY) domain, which is located at the C-terminal end of the photosensory domain, is required for the spectral integrity of phytochrome; however, little is known about the signal transduction activity of this domain. Here, we have established transgenic Arabidopsis thaliana lines expressing an N-terminal 450-amino acid fragment of phyB (N450) lacking the PHY domain on a phyB-deficient background. Analysis of these plants revealed that N450 can act as an active photoreceptor when attached to a short nuclear localization signal and beta-glucuronidase. In vitro spectral analysis of reconstituted chromopeptides further indicated that the stability of the N450 Pfr form, an active form of phytochrome, is markedly reduced in comparison with the Pfr form of full-length phyB. Consistent with this, plants expressing N450 failed to respond to intermittent light applied at long intervals, indicating that N450 Pfr is short-lived in vivo. Taken together, our findings show that the PHY domain is dispensable for phyB signal transduction but is required for stabilizing the Pfr form of phyB.