Clough R C, Casal J J, Jordan E T, Christou P, Vierstra R D
Department of Horticulature, University of Wisconsin-Madison 53706, USA.
Plant Physiol. 1995 Nov;109(3):1039-45. doi: 10.1104/pp.109.3.1039.
To investigate the biological functions of phytochromes in monocots, we generated, by electric discharge particle bombardment, transgenic rice (Oryza sativa cv Gulfmont) that constitutively expresses the oat phytochrome A apoprotein. The introduced 124-kD polypeptide bound chromophore and assembled into a red- and far-red-light-photoreversible chromoprotein with absorbance spectra indistinguishable from those of phytochrome purified from etiolated oats. Transgenic lines expressed up to 3 and 4 times more spectrophotometrically detectable phytochrome than wild-type plants in etiolated and green seedlings, respectively. Upon photo-conversion to the far-red-absorbing form of phytochrome, oat phytochrome A was degraded in etiolated seedlings with kinetics similar to those of endogenous rice phytochromes (half-life approximately 20 min). Although plants overexpressing phytochrome A were phenotypically indistinguishable from wild-type plants when grown under high-fluence white light, they were more sensitive as etiolated seedlings to light pulses that established very low phytochrome equilibria. This indicates that the introduced oat phytochrome A was biologically active. Thus, rice ectopically expressing PHY genes may offer a useful model to help understand the physiological functions of the various phytochrome isoforms in monocotyledonous plants.
为了研究单子叶植物中光敏色素的生物学功能，我们通过放电粒子轰击技术培育出了组成型表达燕麦光敏色素A脱辅基蛋白的转基因水稻（Oryza sativa cv Gulfmont）。导入的124-kD多肽结合了发色团，并组装成一种在红光和远红光下具有光可逆性的色素蛋白，其吸收光谱与从黄化燕麦中纯化得到的光敏色素无法区分。在黄化和绿色幼苗中，转基因株系分别比野生型植株表达出多3至4倍分光光度法可检测到的光敏色素。在光转化为远红光吸收型光敏色素后，燕麦光敏色素A在黄化幼苗中降解，其动力学与内源水稻光敏色素相似（半衰期约20分钟）。尽管在高通量白光下生长时，过量表达光敏色素A的植株在表型上与野生型植株没有区别，但作为黄化幼苗，它们对建立极低光敏色素平衡的光脉冲更为敏感。这表明导入的燕麦光敏色素A具有生物活性。因此，异位表达PHY基因的水稻可能为帮助理解单子叶植物中各种光敏色素亚型的生理功能提供一个有用的模型。
