Molecular Mechanisms of Enhancement of Plant Growth by phototropins.

适当的叶片定位对优化光合作用和植物生长至关重要。我们在这里展示了蓝光刺激下叶片定位的调控。在白光下生长的1周龄拟南芥幼苗，转到25 μmol m-2 s-1的红光下5 d，新生叶柄几乎是水平的，叶片卷曲向下倾斜。当上方微弱蓝光（0.1 μmol m-2 s-1）与红光叠加时，新叶柄斜向上生长，叶片平展。叶片定位需要光致性蛋白1 （phot1）和非光致性下胚轴3 (NPH3)，从而促进植物生长。在一个nph3突变体中，既没有发现最佳的叶片定位，也没有发现蓝光使叶片变平，蓝光诱导的生长增强大大减弱。当蓝光从0.1 μmol m-2 s-1增加到5 μmol m-2 s-1时，phot1和nph3突变体的叶片定位和叶片变平均发生正常，表明在这些响应中，phot2信号开始发挥作用，且信号不依赖于phot1和nph3。当侧面照射0.1 μmol m-2 s-1的蓝光和上方照射红光时，新叶朝向蓝光光源方向生长。我们显示了NPH3的组织表达及其通过螺旋结构域和c端区域的质膜定位。我们认为，nph3介导的趋光素信号通过诱导最佳叶片定位和叶片变平来优化光感知效率，从而促进植物生长。

Appropriate leaf positioning is essential for optimizing photosynthesis and plant growth. We show here the regulation of leaf positioning under blue light stimuli. When one-week-old Arabidopsis seedlings grown under white light were transferred to red light (25 μmol m-2 s-1) for 5 days, new petioles that appeared were almost horizontal and their leaves were curled and slanted downward. However, when a weak blue light from above (0.1 μmol m-2 s-1) was superimposed on red light, the new petioles grew obliquely upward and the leaves were flat and horizontal. The leaf positioning required both phototropin1 (phot1) and non-phototropic hypocotyl 3 (NPH3), and resulted in enhanced plant growth. In an nph3 mutant, neither optimal leaf positioning nor leaf flattening by blue light was found, and blue light-induced growth enhancement was drastically reduced. When blue light was increased from 0.1 μmol m-2 s-1 to 5 μmol m-2 s-1,normal leaf positioning and leaf flattening were induced in both phot1 and nph3 mutants, suggesting that phot2 signaling became functional and that the signaling was independent of phot1 and NPH3 in these responses. When plants were irradiated with blue light (0.1 μmol m-2 s-1) from the side and red light from above, the new leaves became oriented toward the source of blue light. We showed the tissue expression of NPH3 and its plasma membrane localization via the coiled-coil domain and the C-terminus region. We conclude that NPH3-mediated phototropin signaling optimizes the efficiency of light perception by inducing both optimal leaf positioning and leaf flattening, and enhances plant growth.