Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843, USA.
Plant Physiol. 2010 Apr;152(4):1914-27. doi: 10.1104/pp.109.148833. Epub 2010 Feb 12.
The red light:far-red light ratio perceived by phytochromes controls plastic traits of plant architecture, including branching. Despite the significance of branching for plant fitness and productivity, there is little quantitative and mechanistic information concerning phytochrome control of branching responses in Arabidopsis (Arabidopsis thaliana). Here, we show that in Arabidopsis, the negative effects of the phytochrome B mutation and of low red light:far-red light ratio on branching were largely due to reduced bud outgrowth capacity and an increased degree of correlative inhibition acting on the buds rather than due to a reduced number of leaves and buds available for branching. Phytochrome effects on the degree of correlative inhibition required functional BRANCHED1 (BRC1), BRC2, AXR1, MORE AXILLARY GROWTH2 (MAX2), and MAX4. The analysis of gene expression in selected buds indicated that BRC1 and BRC2 are part of different gene networks. The BRC1 network is linked to the growth capacity of specific buds, while the BRC2 network is associated with coordination of growth among branches. We conclude that the branching integrators BRC1 and BRC2 are necessary for responses to phytochrome, but they contribute differentially to these responses, likely acting through divergent pathways.
远红光比值被光敏色素感知，控制着植物结构的可塑性特征，包括分枝。尽管分枝对植物的适应性和生产力具有重要意义，但关于光敏色素对拟南芥分枝反应的控制，我们几乎没有定量和机制方面的信息。在这里，我们表明，在拟南芥中，光敏色素 B 突变和低红光：远红光比值对分枝的负面影响主要归因于芽生长能力的降低和对芽的相关性抑制程度的增加，而不是由于可用于分枝的叶片和芽的数量减少。光敏色素对相关性抑制程度的影响需要 BRANCHED1（BRC1）、BRC2、AXR1、MORE AXILLARY GROWTH2（MAX2）和 MAX4 的功能。对选定芽中基因表达的分析表明，BRC1 和 BRC2 是不同基因网络的一部分。BRC1 网络与特定芽的生长能力有关，而 BRC2 网络与分支之间的生长协调有关。我们得出结论，分枝整合因子 BRC1 和 BRC2 是对光敏色素反应所必需的，但它们对这些反应的贡献不同，可能通过不同的途径发挥作用。
