Reymond P, Short T W, Briggs W R, Poff K L
Department of Plant Biology, Carnegie Institution of Washington, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 1992 May;89(10):4718-21. doi: 10.1073/pnas.89.10.4718.
Blue light is known to cause rapid phosphorylation of a membrane protein in etiolated seedlings of several plant species, a protein that, at least in etiolated pea seedlings and maize coleoptiles, has been shown to be associated with the plasma membrane. The light-driven phosphorylation has been proposed on the basis of correlative evidence to be an early step in the signal transduction chain for phototropism. In the Arabidopsis thaliana mutant JK224, the sensitivity to blue light for induction of first positive phototropism is known to be 20- to 30-fold lower than in wild type, whereas second positive curvature appears to be normal. While light-induced phosphorylation can be demonstrated in crude membrane preparations from shoots of the mutant, the level of phosphorylation is dramatically lower than in wild type, as is the sensitivity to blue light. Another A. thaliana mutant, JK218, that completely lacks any phototropic responses to up to 2 h of irradiation, shows a normal level of light-induced phosphorylation at saturation. Since its gravitropic sensitivity is normal, it is presumably blocked in some step between photoreception and the confluence of the signal transduction pathways for phototropism and gravitropism. We conclude from mutant JK224 that light-induced phosphorylation plays an early role in the signal transduction chain for phototropism in higher plants.
已知蓝光可使几种植物物种的黄化幼苗中的一种膜蛋白快速磷酸化，至少在黄化豌豆幼苗和玉米胚芽鞘中，这种蛋白已被证明与质膜有关。基于相关证据，光驱动的磷酸化被认为是向光性信号转导链中的早期步骤。在拟南芥突变体JK224中，已知其对蓝光诱导首次正向光性的敏感性比野生型低20至30倍，而第二次正向弯曲似乎正常。虽然在突变体芽的粗膜制剂中可以证明光诱导的磷酸化，但磷酸化水平比野生型显著降低，对蓝光的敏感性也是如此。另一个拟南芥突变体JK218，在长达2小时的照射下完全没有任何向光性反应，在饱和状态下显示出正常水平的光诱导磷酸化。由于其重力敏感性正常，推测它在光感受和向光性与向重力性信号转导途径汇合之间的某个步骤中受阻。我们从突变体JK224得出结论，光诱导的磷酸化在高等植物向光性信号转导链中起早期作用。
