Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033 Japan.
Proc Natl Acad Sci U S A. 2011 Jul 5;108(27):11280-4. doi: 10.1073/pnas.1100592108. Epub 2011 Jun 20.
In many phototrophic microorganisms and plants, chloroplasts change their positions relative to the incident light to achieve optimal photosynthesis. In the case of motile green algae, cells change their swimming direction by switching between positive and negative phototaxis, i.e., swimming toward or away from the light source, depending on environmental and internal conditions. However, little is known about the molecular signals that determine the phototactic direction. Using the green alga Chlamydomonas reinhardtii, we found that cellular reduction-oxidation (redox) poise plays a key role: Cells always exhibited positive phototaxis after treatment with reactive oxygen species (ROS) and always displayed negative phototaxis after treatment with ROS quenchers. The redox-dependent switching of the sign of phototaxis may contribute in turn to the maintenance of cellular redox homeostasis.
在许多光合微生物和植物中，叶绿体相对于入射光改变位置以实现最佳光合作用。对于运动性绿藻，细胞通过在正向和负向趋光性之间切换来改变其游动方向，即根据环境和内部条件向光源或远离光源游动。然而，关于决定趋光性方向的分子信号知之甚少。使用绿藻莱茵衣藻，我们发现细胞氧化还原（redox）平衡状态起着关键作用：细胞在用活性氧（ROS）处理后总是表现出正向趋光性，在用 ROS 清除剂处理后总是表现出负向趋光性。趋光性标志的这种依赖于氧化还原的转换可能反过来有助于维持细胞氧化还原平衡。
