Green R M, Tobin E M
Department of Molecular, Cell, and Developmental Biology, University of California, Box 951606, Los Angeles, CA 90095-1606, USA.
Proc Natl Acad Sci U S A. 1999 Mar 30;96(7):4176-9. doi: 10.1073/pnas.96.7.4176.
Little is known about plant circadian oscillators, in spite of how important they are to sessile plants, which require accurate timekeepers that enable the plants to respond to their environment. Previously, we identified a circadian clock-associated (CCA1) gene that encodes an Myb-related protein that is associated with phytochrome control and circadian regulation in plants. To understand the role CCA1 plays in phytochrome and circadian regulation, we have isolated an Arabidopsis line with a T DNA insertion that results in the loss of CCA1 RNA, of CCA1 protein, and of an Lhcb-promoter binding activity. This mutation affects the circadian expression of all four clock-controlled genes that we examined. The results show that, despite their similarity, CCA1 and LHY are only partially redundant. The lack of CCA1 also affects the phytochrome regulation of gene expression, suggesting that CCA1 has an additional role in a signal transduction pathway from light, possibly acting at the point of integration between phytochrome and the clock. Our results indicate that CCA1 is an important clock-associated protein involved in circadian regulation of gene expression.
尽管植物生物钟振荡器对固着生长的植物非常重要，因为这些植物需要精确的计时机制来使其能够响应环境，但我们对它们的了解却很少。此前，我们鉴定出了一个与生物钟相关的（CCA1）基因，该基因编码一种与植物光敏色素控制和生物钟调节相关的Myb相关蛋白。为了了解CCA1在光敏色素和生物钟调节中所起的作用，我们分离出了一个拟南芥株系，该株系因T-DNA插入导致CCA1 RNA、CCA1蛋白以及Lhcb启动子结合活性丧失。这种突变影响了我们所检测的所有四个生物钟控制基因的昼夜节律表达。结果表明，尽管CCA1和LHY相似，但它们只是部分冗余。CCA1的缺失还影响了基因表达的光敏色素调节，这表明CCA1在光信号转导途径中具有额外作用，可能作用于光敏色素与生物钟的整合点。我们的结果表明，CCA1是一种重要的与生物钟相关的蛋白，参与基因表达的昼夜节律调节。
