Lariguet Patricia, Schepens Isabelle, Hodgson Daniel, Pedmale Ullas V, Trevisan Martine, Kami Chitose, de Carbonnel Matthieu, Alonso José M, Ecker Joseph R, Liscum Emmanuel, Fankhauser Christian
Department of Molecular Biology, University of Geneva, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
Proc Natl Acad Sci U S A. 2006 Jun 27;103(26):10134-9. doi: 10.1073/pnas.0603799103. Epub 2006 Jun 15.
Phototropism, or plant growth in response to unidirectional light, is an adaptive response of crucial importance. Lateral differences in low fluence rates of blue light are detected by phototropin 1 (phot1) in Arabidopsis. Only NONPHOTOTROPIC HYPOCOTYL 3 (NPH3) and root phototropism 2, both belonging to the same family of proteins, have been previously identified as phototropin-interacting signal transducers involved in phototropism. PHYTOCHROME KINASE SUBSTRATE (PKS) 1 and PKS2 are two phytochrome signaling components belonging to a small gene family in Arabidopsis (PKS1-PKS4). The strong enhancement of PKS1 expression by blue light and its light induction in the elongation zone of the hypocotyl prompted us to study the function of this gene family during phototropism. Photobiological experiments show that the PKS proteins are critical for hypocotyl phototropism. Furthermore, PKS1 interacts with phot1 and NPH3 in vivo at the plasma membrane and in vitro, indicating that the PKS proteins may function directly with phot1 and NPH3 to mediate phototropism. The phytochromes are known to influence phototropism but the mechanism involved is still unclear. We show that PKS1 induction by a pulse of blue light is phytochrome A-dependent, suggesting that the PKS proteins may provide a molecular link between these two photoreceptor families.
向光性，即植物对单向光的生长反应，是一种至关重要的适应性反应。拟南芥中的向光素1（phot1）可检测蓝光低光通量率的横向差异。此前，只有属于同一蛋白家族的非向光性下胚轴3（NPH3）和根向光性2被鉴定为参与向光性的与向光素相互作用的信号转导因子。植物色素激酶底物（PKS）1和PKS2是拟南芥中一个小基因家族（PKS1 - PKS4）的两个植物色素信号转导成分。蓝光对PKS1表达的强烈增强作用及其在下胚轴伸长区的光诱导作用促使我们研究该基因家族在向光性过程中的功能。光生物学实验表明，PKS蛋白对下胚轴向光性至关重要。此外，PKS1在体内和体外的质膜上均与phot1和NPH3相互作用，这表明PKS蛋白可能直接与phot1和NPH3共同作用来介导向光性。已知植物色素会影响向光性，但其中涉及的机制仍不清楚。我们发现蓝光脉冲对PKS1的诱导是依赖于光敏色素A的，这表明PKS蛋白可能在这两个光受体家族之间提供了一个分子联系。
