Molecular Mechanisms of Enhancement of Plant Growth by phototropins.

点击翻译按钮获取中文摘要

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.