生物谷：在发表于《生物化学杂志》（Journal of Biological Chemistry）上的文章中，来自Missouri-Columbia大学的科学家报道了他们在植物趋光性机制的分子水平上的新发现，趋光性是植物向着或背离光线生长的一种现象。
趋光作用通过植物中的光感受器探测到有方向性的蓝光而激发。MU的生物科学系教授MannieLiscum表示，了解这一机制对于提高农作物的种植水平有着非常重要的意义。
Liscum说：“通过了解趋光性的分子机制，我们就可以提高植物的单位面积数量，并增加其耐旱性。例如，可以通过这些机制来优化植物捕捉阳光进行光合作用的能力，这能使植物获得更多能量，从而带来更好的生长等农业有力因素。”
Liscum和博士生UllasPedmale研究了拟南芥中的趋光性信号的调节过程，拟南芥是一种常用于实验室研究的模式植物。小组主要分析了一种对于趋光性非常关键的蛋白NPH3，他们研究了这一蛋白的磷酸化作用。利用一系列分析方法，小组发现幼苗在黑暗中生长过程中的NPH3是一种被磷酸化的蛋白。而当它们暴露于阳光下时，NPH3变得去磷酸化。
以上结果显示，控制趋光性的主要感受器phot1吸收光将导致NPH3去除磷酸基，从而使得趋光信号能进一步传递。
Liscum说：“我们发现暴露于蓝光下时NPH3将去磷酸化，这一过程通过蓝光激活phot1而实现。”Liscum和Pedmale目前计划进一步研究哪一个氨基酸决定了NPH3的这一可逆磷酸化过程以及NPH3在植物的其它过程中起到的作用。（援引 教育部科技发展中心）
原文链接：http://www.physorg.com/news102871414.html
原始出处:
Originally published In Press as doi:10.1074/jbc.M702551200 on May 10, 2007
J. Biol. Chem., Vol. 282, Issue 27, 19992-20001, July 6, 2007
Regulation of Phototropic Signaling in Arabidopsis via Phosphorylation State Changes in the Phototropin 1-interacting Protein NPH3*
Ullas V. Pedmale and Emmanuel Liscum1
From the Division of Biological Sciences and the Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
Phototropism, or the directional growth (curvature) of various organs toward or away from incident light, represents a ubiquitous adaptive response within the plant kingdom. This response is initiated through the sensing of directional blue light (BL) by a small family of photoreceptors known as the phototropins. Of the two phototropins present in the model plant Arabidopsis thaliana, phot1 (phototropin 1) is the dominant receptor controlling phototropism. Absorption of BL by the sensory portion of phot1 leads, as in other plant phototropins, to activation of a C-terminal serine/threonine protein kinase domain, which is tightly coupled with phototropic responsiveness. Of the five phot1-interacting proteins identified to date, only one, NPH3 (non-phototropic hypocotyl 3), is essential for all phot1-dependent phototropic responses, yet little is known about how phot1 signals through NPH3. Here, we show that, in dark-grown seedlings, NPH3 exists as a phosphorylated protein and that BL stimulates its dephosphorylation. phot1 is necessary for this response and appears to regulate the activity of a type 1 protein phosphatase that catalyzes the reaction. The abrogation of both BL-dependent dephosphorylation of NPH3 and development of phototropic curvatures by protein phosphatase inhibitors further suggests that this post-translational modification represents a crucial event in phot1-dependent phototropism. Given that NPH3 may represent a core component of a CUL3-based ubiquitin-protein ligase (E3), we hypothesize that the phosphorylation state of NPH3 determines the functional status of such an E3 and that differential regulation of this E3 is required for normal phototropic responsiveness.
