Lin C, Ahmad M, Gordon D, Cashmore A R
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
Proc Natl Acad Sci U S A. 1995 Aug 29;92(18):8423-7. doi: 10.1073/pnas.92.18.8423.
The Arabidopsis HY4 gene, required for blue-light-induced inhibition of hypocotyl elongation, encodes a 75-kDa flavoprotein (CRY1) with characteristics of a blue-light photoreceptor. To investigate the mechanism by which this photoreceptor mediates blue-light responses in vivo, we have expressed the Arabidopsis HY4 gene in transgenic tobacco. The transgenic plants exhibited a short-hypocotyl phenotype under blue, UV-A, and green light, whereas they showed no difference from the wild-type plant under red/far-red light or in the dark. This phenotype was found to cosegregate with overexpression of the HY4 transgene and to be fluence dependent. We concluded that the short-hypocotyl phenotype of transgenic tobacco plants was due to hypersensitivity to blue, UV-A, and green light, resulting from over-expression of the photoreceptor. These observations are consistent with the broad action spectrum for responses mediated by this cryptochrome in Arabidopsis and indicate that the machinery for signal, transduction required by the CRY1 protein is conserved among different plant species. Furthermore, the level of these photoresponses is seen to be determined by the cellular concentration of this photoreceptor.
拟南芥HY4基因是蓝光诱导下抑制下胚轴伸长所必需的，它编码一种具有蓝光光感受器特征的75 kDa黄素蛋白（CRY1）。为了研究这种光感受器在体内介导蓝光反应的机制，我们在转基因烟草中表达了拟南芥HY4基因。转基因植株在蓝光、UV-A和绿光下表现出下胚轴短的表型，而在红光/远红光下或黑暗中与野生型植株没有差异。发现这种表型与HY4转基因的过表达共分离，并且是光通量依赖性的。我们得出结论，转基因烟草植株下胚轴短的表型是由于光感受器的过表达导致对蓝光、UV-A和绿光超敏。这些观察结果与拟南芥中这种隐花色素介导的反应的广泛作用光谱一致，表明CRY1蛋白所需的信号转导机制在不同植物物种中是保守的。此外，这些光反应的水平似乎由这种光感受器的细胞浓度决定。
