Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1405BWE Buenos Aires, Argentina.
Proc Natl Acad Sci U S A. 2010 Mar 9;107(10):4776-81. doi: 10.1073/pnas.0910446107. Epub 2010 Feb 22.
Plants use light as a source of energy for photosynthesis and as a source of environmental information perceived by photoreceptors. Testing whether plants can complete their cycle if light provides energy but no information about the environment requires a plant devoid of phytochromes because all photosynthetically active wavelengths activate phytochromes. Producing such a quintuple mutant of Arabidopsis thaliana has been challenging, but we were able to obtain it in the flowering locus T (ft) mutant background. The quintuple phytochrome mutant does not germinate in the FT background, but it germinates to some extent in the ft background. If germination problems are bypassed by the addition of gibberellins, the seedlings of the quintuple phytochrome mutant exposed to red light produce chlorophyll, indicating that phytochromes are not the sole red-light photoreceptors, but they become developmentally arrested shortly after the cotyledon stage. Blue light bypasses this blockage, rejecting the long-standing idea that the blue-light receptors cryptochromes cannot operate without phytochromes. After growth under white light, returning the quintuple phytochrome mutant to red light resulted in rapid senescence of already expanded leaves and severely impaired expansion of new leaves. We conclude that Arabidopsis development is stalled at several points in the presence of light suitable for photosynthesis but providing no photomorphogenic signal.
植物将光作为光合作用的能量来源，并将光作为光受体感知的环境信息的来源。如果光提供能量但没有有关环境的信息，那么测试植物是否可以完成其周期，这就需要一种不含光敏色素的植物，因为所有光合有效波长都会激活光敏色素。生产拟南芥的这种五倍体光敏色素突变体具有挑战性，但我们能够在开花位点 T（ft）突变体背景下获得它。在 FT 背景下，五倍体光敏色素突变体不会发芽，但在 ft 背景下会在一定程度上发芽。如果通过添加赤霉素来避免发芽问题，那么在红光下暴露的五倍体光敏色素突变体的幼苗会产生叶绿素，这表明光敏色素不是唯一的红光光受体，但在子叶阶段后不久，它们会发育停滞。蓝光绕过此阻断，否定了蓝敏受体隐花色素在没有光敏色素的情况下无法运作的长期观点。在白光下生长后，将五倍体光敏色素突变体返回红光会导致已经展开的叶子迅速衰老，并严重损害新叶子的扩展。我们得出的结论是，在适合光合作用但没有光形态发生信号的光存在下，拟南芥的发育会停滞在几个点上。
