Sommer D, Wells T A, Song P S
Department of Chemistry, University of Nebraska-Lincoln 68588, USA.
FEBS Lett. 1996 Sep 16;393(2-3):161-6. doi: 10.1016/0014-5793(96)00876-9.
Red/far-red light signal transduction by the phytochrome family of photoreceptors regulates plant growth and development. We investigated the possibility that tyrosine kinases and/or phosphatases are involved in phytochrome-mediated signal transduction using crude extracts of oat seedlings that are grown in the dark. We found that a 124 kDa protein was tyrosine-phosphorylated as determined by Western blotting with a phosphotyrosine-specific monoclonal antibody. The 124 kDa protein was recognized by the anti-phosphotyrosine antibody in anti-phytochrome A immunoprecipitates. The level of anti-phosphotyrosine antibody binding to the 124 kDa protein(s) in phytochrome immunoprecipitates that had been treated with red light prior to immunoprecipitation decreased relative to dark controls. These results suggest that either phytochrome from dark-grown seedlings is tyrosine phosphorylated or that it co-immunoprecipitates with a phosphotyrosine-containing protein of the same molecular weight. The implications of these results in the regulation of (a) the putative Ser/Thr kinase activity of the photoreceptor and (b) the binding of signaling molecules, such as phospholipase C to phytochrome, are discussed.
由光敏色素家族光感受器介导的红光/远红光信号转导调控植物的生长和发育。我们利用在黑暗中生长的燕麦幼苗的粗提物，研究了酪氨酸激酶和/或磷酸酶参与光敏色素介导的信号转导的可能性。我们发现，用磷酸酪氨酸特异性单克隆抗体进行蛋白质免疫印迹分析时，一种124 kDa的蛋白质发生了酪氨酸磷酸化。在抗光敏色素A免疫沉淀物中，抗磷酸酪氨酸抗体识别出了这种124 kDa的蛋白质。在免疫沉淀前用红光处理过的光敏色素免疫沉淀物中，抗磷酸酪氨酸抗体与124 kDa蛋白质的结合水平相对于黑暗对照组有所降低。这些结果表明，要么来自黑暗生长幼苗的光敏色素发生了酪氨酸磷酸化，要么它与相同分子量的含磷酸酪氨酸的蛋白质发生了共免疫沉淀。本文讨论了这些结果对（a）光感受器假定的丝氨酸/苏氨酸激酶活性的调控以及（b）信号分子（如磷脂酶C）与光敏色素结合的影响。
