Cryptochrome 1 and phytochrome B control shade-avoidance responses in Arabidopsis via partially independent hormonal cascades.
Cryptochrome 1 and phytochrome B control shade-avoidance responses in Arabidopsis via partially independent hormonal cascades.
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DOI：
10.1111/j.1365-313x.2011.04598.x
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发表时间：
2011-07
期刊：
影响因子：
--
通讯作者：
Ballaré CL
中科院分区：
文献类型：
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作者：
Keller MM;Jaillais Y;Pedmale UV;Moreno JE;Chory J;Ballaré CL
由于其他植物的接近，植物对光的红/远红比（R:FR）的减少做出反应，通过启动形态变化来改善光捕获。在拟南芥中，这种反应（遮荫回避综合征，SAS）由光敏色素（特别是phyB）控制，并依赖于生长素生物合成的TAA1途径。然而，当在真正的冠层中生长时，我们发现phyB突变体和TAAI （sav3）缺陷突变体对种植密度和叶片遮荫的增加仍然表现出强大的SAS响应。将植物暴露在蓝光衰减环境下，可以得到SAS形态（叶片低矮化和叶片/叶柄比降低）的表型。这些对蓝光衰减的响应需要UV-A/蓝光感光细胞cry1。此外，它们是通过与phyB失活募集的途径有限重叠的机制介导的。特别是，极地生长素运输、生长素生物合成和赤霉素信号通路参与了SAS对低R:FR的反应，而SAS对蓝光枯竭的反应并不需要这些途径。相比之下，油菜素内酯反应似乎是低蓝光下SAS表型完全表达所必需的。phyB和cry1失活途径似乎在对基本/螺旋-环-螺旋（bHLH）转录因子光敏色素相互作用因子4和5 （PIF4和PIF5）的需求上趋同，从而引发SAS表型。我们的研究结果表明，蓝光是SAS响应的重要控制因素，PIF4和PIF5是控制冠层植物结构的多种信号通路的关键枢纽。
Plants respond to a reduction in the red/far-red ratio (R:FR) of light, caused by the proximity of other plants, by initiating morphological changes that improve light capture. In Arabidopsis, this response (shade avoidance syndrome, SAS) is controlled by phytochromes (particularly phyB), and is dependent on the TAA1 pathway of auxin biosynthesis. However, when grown in real canopies, we found that phyB mutants and mutants deficient in TAAI (sav3) still display robust SAS responses to increased planting density and leaf shading. The SAS morphology (leaf hyponasty and reduced lamina/petiole ratio) could be phenocopied by exposing plants to blue light attenuation. These responses to blue light attenuation required the UV-A/blue light photoreceptor cry1. Moreover, they were mediated through mechanisms that showed only limited overlap with the pathways recruited by phyB inactivation. In particular, pathways for polar auxin transport, auxin biosynthesis and gibberellin signaling that are involved in SAS responses to low R:FR were not required for the SAS responses to blue light depletion. By contrast, the brassinosteroid response appeared to be required for the full expression of the SAS phenotype under low blue light. The phyB and cry1 inactivation pathways appeared to converge in their requirement for the basic/helix-loop-helix (bHLH) transcription factors PHYTOCHROME INTERACTING FACTORs 4 and 5 (PIF4 and PIF5) to elicit the SAS phenotype. Our results suggest that blue light is an important control of SAS responses, and that PIF4 and PIF5 are critical hubs for a diverse array of signaling routes that control plant architecture in canopies.