Yang Ming-Tzong, Chen Shu-Ling, Lin Chu-Yung, Chen Yih-Ming
Institute of Plant Biology, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd, Taipei, 106, Taiwan (ROC).
Planta. 2005 Jun;221(3):374-85. doi: 10.1007/s00425-004-1451-y. Epub 2004 Dec 15.
Etiolated leaves of 28 degrees C-dark-grown mung bean (Vigna radiata L. cv. 2937) seedlings fail to turn green after being shifted to a light and cold environment. At the visible phenotypic level, incapability of leaf greening is the only failure event for the de-etiolation of mung bean seedlings at low temperature. Ultrastructural studies revealed that chloroplast development was completely suppressed by chilling treatment. A cDNA library originating from 28 degrees C-light-grown seedling leaves was constructed for screening cold-suppressed (cos) genes. Thirteen full-length cDNA clones were obtained, with 12 clones encoding chloroplast proteins, which, according to their known physiological functions, were important for chloroplast development and photosynthesis. Another cos cDNA encodes CYP90A2, which is a cytochrome P450 protein involved in the biosynthesis of brassinosteroid hormones. All cos genes are light-regulated at normal temperature. The influence of chilling stress on cos expression was examined in 10 degrees C-light- and 10 degrees C-dark-grown etiolated seedlings, and in 10 degrees C-light-grown green plants. The data show that cos expression in these three treatments is severely suppressed. This suppression is controlled at the transcriptional level, as demonstrated by nuclear runoff experiments, and is reversible because cos mRNAs accumulate again after the cold-treated plants have been transferred to 28 degrees C.
在28摄氏度黑暗环境中生长的绿豆（Vigna radiata L. cv. 2937）幼苗的黄化叶片转移到光照和低温环境后无法变绿。在可见表型水平上，叶片无法变绿是绿豆幼苗在低温下脱黄化过程中唯一的失败事件。超微结构研究表明，低温处理完全抑制了叶绿体的发育。构建了一个来自28摄氏度光照下生长的幼苗叶片的cDNA文库，用于筛选冷抑制（cos）基因。获得了13个全长cDNA克隆，其中12个克隆编码叶绿体蛋白，根据其已知的生理功能，这些蛋白对叶绿体发育和光合作用很重要。另一个cos cDNA编码CYP90A2，它是一种参与油菜素类固醇激素生物合成的细胞色素P450蛋白。所有cos基因在正常温度下都受光照调节。在10摄氏度光照和10摄氏度黑暗中生长的黄化幼苗以及10摄氏度光照下生长的绿色植物中检测了低温胁迫对cos表达的影响。数据表明，这三种处理中cos的表达都受到严重抑制。如核转录实验所示，这种抑制是在转录水平上控制的，并且是可逆的，因为在冷处理的植物转移到28摄氏度后，cos mRNA会再次积累。
