Department of Biological Sciences, Science Laboratory Building 3326, Southern Illinois University, Edwardsville, IL 62026, USA.
J Exp Bot. 2010 Oct;61(15):4387-97. doi: 10.1093/jxb/erq242. Epub 2010 Aug 6.
In Arabidopsis thaliana, chloroplasts move towards the periclinal cell walls upon exposure to low blue light intensities and to anticlinal walls under high light. The regulation of these chloroplast movements involves members of both the phototropin and phytochrome families of photoreceptors. Examination of fluence-rate response dependencies in phot1 and phot2 mutants revealed that although both photoreceptors are capable of inducing chloroplast accumulation under low-light conditions, the signals from these photoreceptors appear to be antagonistic. Chloroplast movements in wild-type plants were intermediate between those of the single phot mutants, consistent with each operating through separate signalling cascades. Mutants in phot2 showed transient chloroplast avoidance responses upon exposure to intense blue light, and slow but sustained chloroplast avoidance under intense white light, indicating that in the absence of phot2, phot1 is capable of generating both a low and a high-light response signal. Mutations in phytochrome B (phyB) caused an enhanced avoidance response at intermediate and high light intensities. Examination of phyB, phot1phyB, and phot2phyB mutants indicated that this enhancement is caused by PhyB inhibition of the high-light avoidance response in wild-type plants. In addition, our results suggest that the inhibition by PhyB is not exclusive to either of the phot1 or phot2 signalling pathways.
在拟南芥中,当暴露在低蓝光强度下时,叶绿体向周壁细胞移动,而在高光下则向垂周壁移动。这些叶绿体运动的调节涉及到光受体中的光敏色素和向光素家族的成员。对 phot1 和 phot2 突变体的光强响应依赖性的研究表明,尽管这两种光受体都能够在低光条件下诱导叶绿体积累,但这些光受体的信号似乎是拮抗的。在野生型植物中,叶绿体运动介于单个 phot 突变体之间,这与每个信号转导途径分别独立作用是一致的。在 phot2 突变体中,当暴露于强蓝光下时,叶绿体会出现短暂的回避反应,而在强白光下则会出现缓慢但持续的叶绿体回避反应,这表明在没有 phot2 的情况下,phot1 能够产生低光和高光响应信号。光敏色素 B (phyB) 的突变导致在中等和高光强下出现增强的回避反应。对 phyB、phot1phyB 和 phot2phyB 突变体的研究表明,这种增强是由 PhyB 抑制野生型植物中的高光回避反应引起的。此外,我们的结果表明,PhyB 的抑制作用并不是 phot1 或 phot2 信号通路所独有的。