Department of Plant Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
EMBO J. 1985 Feb;4(2):291-5. doi: 10.1002/j.1460-2075.1985.tb03628.x.
Spirodela oligorrhiza plants were used to study direct effects of light on plastid gene expression uncoupled from sequential chloroplast-developmental processes. Specific transcript levels were analysed using chloroplast, gene-fragment probes. Protein synthesis in vivo and in vitro was also measured. In tissue with mature chloroplasts, light/dark regimes had no substantial effect on transcript levels of the psbA gene coding for the 32-kd protein. However, under the same conditions, synthesis of the protein itself was dramatically affected. We conclude that in mature chloroplasts synthesis of 32-kd protein is regulated mainly at a translational level. Transcript levels of the rbcL gene, coding for the large subunit of ribulosebisphosphate carboxylase-oxygenase, were somewhat sensitive to light/dark effects, although not to the same degree as was synthesis of the protein. We conclude that translational events and transcript levels are involved in regulating synthesis of this polypeptide. Carbon deprivation in the dark reduced psbA and rbcL transcript levels appreciably below those found in non-starved, dark-grown tissue. This suggests that starvation and dark effects must be experimentally separated from each other for valid conclusions to be drawn about light/dark regulation of chloroplast gene expression.
采用轮藻植物来研究光对于与叶绿体发育顺序过程相分离的质体基因表达的直接影响。利用叶绿体基因片段探针分析特定的转录水平。还测量了体内和体外的蛋白质合成。在具有成熟叶绿体的组织中，光照/黑暗周期对编码 32kd 蛋白的 psbA 基因的转录水平没有实质性影响。然而，在相同条件下，蛋白质本身的合成受到显著影响。我们的结论是，在成熟的叶绿体中，32kd 蛋白的合成主要在翻译水平上受到调控。编码核酮糖二磷酸羧化酶-加氧酶大亚基的 rbcL 基因的转录水平对光照/黑暗效应有些敏感，尽管不如蛋白质的合成敏感。我们的结论是，翻译事件和转录水平参与调节该多肽的合成。黑暗中碳饥饿会使 psbA 和 rbcL 转录水平明显低于非饥饿、黑暗生长组织中的水平。这表明，为了得出关于叶绿体基因表达的光照/黑暗调控的有效结论，必须将饥饿和黑暗效应从实验上彼此分离。
