Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, WI 53706, USA.
Plant J. 2010 Apr;62(2):179-91. doi: 10.1111/j.1365-313X.2010.04137.x. Epub 2010 Jan 18.
During seedling establishment, blue and red light suppress hypocotyl growth through the cryptochrome 1 (cry1) and phytochrome B (phyB) photosensory pathways, respectively. How these photosensory pathways integrate with growth control mechanisms to achieve the appropriate degree of stem elongation was investigated by combining cry1 and phyB photoreceptor mutations with genetic manipulations of a multidrug resistance-like membrane protein known as ABCB19 that influenced auxin distribution within the plant, as evidenced by a combination of reporter gene assays and direct auxin measurements. Auxin signaling and ABCB19 protein levels, hypocotyl growth rates, and apical hook opening were measured in mutant and wild-type seedlings exposed to a range of red and blue light conditions. Ectopic/overexpression of ABCB19 (B19OE) greatly increased auxin in the hypocotyl, which reduced the sensitivity of hypocotyl growth specifically to blue light in long-term assays and red light in high-resolution, short-term assays. Loss of ABCB19 partially suppressed the cry1 hypocotyl growth phenotype in blue light. Hypocotyl growth of B19OE seedlings in red light was very similar to phyB mutants. Altered auxin distribution in B19OE seedlings also affected the opening of the apical hook. The cry1 and phyB photoreceptor mutations both increased ABCB19 protein levels at the plasma membrane, as measured by confocal microscopy. The B19OE plant proved to be a useful tool for determining aspects of the mechanism by which light, acting through cry1 or phyB, influences the auxin transport process to control hypocotyl growth during de-etiolation.
在幼苗建立过程中，蓝光和红光分别通过隐花色素 1（cry1）和光敏色素 B（phyB）感光途径抑制下胚轴生长。通过将 cry1 和 phyB 光受体突变与已知影响植物内生长素分布的多药耐药样膜蛋白 ABCB19 的遗传操作相结合，研究了这些感光途径如何与生长控制机制整合以实现适当的茎伸长程度，这一点通过报告基因测定和直接生长素测量的组合得到了证明。在暴露于一系列红光和蓝光条件下，测量了突变体和野生型幼苗中的生长素信号和 ABCB19 蛋白水平、下胚轴生长速率和顶端钩开口。ABCB19（B19OE）的异位/过表达大大增加了下胚轴中的生长素，这降低了下胚轴生长对蓝光的敏感性，特别是在长期测定中，以及在高分辨率、短期测定中对红光的敏感性。ABCB19 的缺失部分抑制了 cry1 在下胚轴中生长的表型在蓝光下。B19OE 幼苗在红光下的下胚轴生长与 phyB 突变体非常相似。B19OE 幼苗中生长素分布的改变也影响了顶端钩的开口。如共焦显微镜测量所示，cry1 和 phyB 光受体突变均增加了质膜上的 ABCB19 蛋白水平。B19OE 植物被证明是一种有用的工具，可用于确定光通过 cry1 或 phyB 作用影响生长素运输过程以控制脱黄化过程中下胚轴生长的机制的各个方面。
