College of Life Sciences, Hunan University, Changsha, China.
J Exp Bot. 2013 Feb;64(4):1017-24. doi: 10.1093/jxb/ers376. Epub 2013 Jan 10.
Branching is an important trait of plant development regulated by environmental signals. Phytochromes in Arabidopsis mediate branching in response to the changes in the red light:far-red light ratio (R:FR), the mechanisms of which are still elusive. Here it is shown that overexpression of CONSTANS-LIKE 7 (COL7) results in an abundant branching phenotype which could be efficiently suppressed by shade or a simulated shade environment (low R:FR). Moreover, col7 mutants develop shorter hypocotyls and COL7 overexpression lines develop longer hypocotyls in comparison with the wild type in low R:FR, indicating that COL7 acts as an enhancer of the shade avoidance response. In shade or transient low R:FR, transcriptional and post-transcriptional expression levels of COL7 are up-regulated and positively associated with rapid mRNA accumulation of PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1), a marker gene of shade avoidance syndrome (SAS). Taken together, the results suggest a dual role for COL7 which promotes branching in high R:FR conditions but enhances SAS in low R:FR conditions.
分枝是植物发育的一个重要特征，受环境信号调控。拟南芥中的光敏色素通过感知红光与远红光的比值（R:FR）的变化来介导分枝，但其具体机制尚不清楚。本研究表明，过量表达 CONSTANS-LIKE 7（COL7）会导致大量分枝表型，该表型可被遮荫或模拟遮荫环境（低 R:FR）有效抑制。此外，与野生型相比，col7 突变体在低 R:FR 下下胚轴较短，而 COL7 过表达系的下胚轴较长，这表明 COL7 作为避荫反应增强子发挥作用。在遮荫或短暂的低 R:FR 条件下，COL7 的转录和转录后表达水平上调，并与避荫综合征（SAS）的标记基因 PHYTOCHROME INTERACTING FACTOR 3-LIKE 1（PIL1）的快速 mRNA 积累呈正相关。综上所述，这些结果表明 COL7 具有双重作用，即在高 R:FR 条件下促进分枝，但在低 R:FR 条件下增强 SAS。
