Janoudi A K, Gordon W R, Wagner D, Quail P, Poff K L
Michigan State University, Department of Energy Plant Research Laboratory, East Lansing 48824, USA.
Plant Physiol. 1997 Mar;113(3):975-9. doi: 10.1104/pp.113.3.975.
The amplitude of phototropic curvature to blue light is enhanced by a prior exposure of seedlings to red light. This enhancement is mediated by phytochrome. Fluence-response relationships have been constructed for red-light-induced enhancement in the phytochrome A (phyA) null mutant, the phytochrome B- (phyB) deficient mutant, and in two transgenic lines of Rabidopsis thaliana that overexpress either phyA or phyB. These fluence-response relationships demonstrate the existence of two response in enhancement, a response in the very-low-to-low-fluence range, and a response in the high-fluence range. Only the response in the high-fluence range is present in the phyA null mutant. In contrast, the phyB-deficient mutant is indistinguishable from the wild-type parent in red-light responsiveness. These data indiacate that phyA is necessary for the very-low-to-low but not the high-influence response, and that phyB is not necessary for either response range. Based on these results, the high-fluence response, if controlled by a single phytochrome, must be controlled by aphytochorme other than phyA of phyB. Overexpression of phyA has a negative effect and overexpression of phyB has an enhancing effect in the high-fluence range. These results suggest that overexpression of either phytochrome perturbs the function of the endogenous photoreceptor system in an unpredictable fashion.
幼苗预先暴露于红光下会增强其对蓝光的向光弯曲幅度。这种增强作用是由光敏色素介导的。已构建了光敏色素A（phyA）缺失突变体、光敏色素B（phyB）缺陷突变体以及两种过表达phyA或phyB的拟南芥转基因系中红光诱导增强作用的光通量-反应关系。这些光通量-反应关系表明增强作用中存在两种反应，一种是极低至低光通量范围内的反应，另一种是高光通量范围内的反应。phyA缺失突变体中仅存在高光通量范围内的反应。相比之下，phyB缺陷突变体在红光反应性方面与野生型亲本没有区别。这些数据表明，phyA对于极低至低光通量反应是必需的，但对于高光通量反应不是必需的，并且phyB对于任何一个反应范围都不是必需的。基于这些结果，如果高光通量反应由单一光敏色素控制，那么它一定是由phyA或phyB以外的光敏色素控制的。在高光通量范围内，phyA的过表达具有负面影响，而phyB的过表达具有增强作用。这些结果表明，任何一种光敏色素的过表达都会以不可预测的方式扰乱内源性光受体系统的功能。
