Abstract：
Light affects almost every aspect of plant development. It is perceived by photoreceptors, among which phytochromes (PHY) are responsible for monitoring the red and far-red spectrum. Arabidopsis thaliana possesses five phytochrome genes (phyA-E). Whereas functions of phyA and phyB are extensively studied, our knowledge on other phytochromes is still rudimentary. To analyze phyD function we expressed it at high levels in different phytochrome-deficient genetic backgrounds. Overexpressed phyD-YFP can govern effective light signaling but only at low temperature and in cooperation with functional phyC. Under these conditions, phyD-YFP accumulates to high levels and opposite to phyB, this pool is stable in light. By comparing the photoconvertible phyD-YFP and phyB levels and their signaling in continuous and pulsed irradiation, we showed that phyD-YFP is a less efficient photoreceptor than phyB. This conclusion is supported by the facts that only a part of the phyD-YFP pool is photoconvertible and thermal reversion of phyD-YFP is faster than that of phyB. Our data suggest that the temperature-dependent function of phyD is based on the amount of phyD protein and not on its Pfr stability, as described for phyB. We also found that phyD-YFP and phyB-GFP associate with strongly overlapping genomic locations and mediate similar changes in gene expression, however the efficiency of phyD-YFP is lower. Based on these data we propose that under certain conditions, synergistic interaction of phyD and phyC can substitute phyB function in seedlings and in adult plants, thus increases the ability of plants to respond more flexibly to environmental changes.
摘要：
光几乎影响植物发育的各个方面。它被光感受器感知，其中植物色素（PHY）负责监测红色和远红色光谱。拟南芥具有5个植物色素基因(phyA-E)。虽然phyA和phyB的功能被广泛研究，我们对其他植物色素的了解仍然很初级。为了分析phyD功能，我们在不同的植物色素缺陷遗传背景中以高水平表达了它。过表达的phyD-YFP可以控制有效的光信号，但只能在低温下并与功能性phyC合作。在这些条件下,phyD-YFP积累到高水平，与phyB相反，这个游泳池在光线下很稳定。通过比较连续和脉冲照射中光可转化的phyD-YFP和phyB水平及其信号传导，我们表明，phyD-YFP是一种效率低于phyB的光感受器。这一结论得到了以下事实的支持：只有一部分phyD-YFP池可以光转换，并且phyD-YFP的热恢复比phyB快。我们的数据表明，phyD的温度依赖性功能是基于phyD蛋白的量而不是其Pfr稳定性。如phyB所述。我们还发现，phyD-YFP和phyB-GFP与强烈重叠的基因组位置相关，并介导基因表达的相似变化。然而，phyD-YFP的效率较低。根据这些数据，我们提出在一定条件下，phyD和phyC的协同相互作用可以替代幼苗和成年植物中的phyB功能，从而提高了植物对环境变化做出更灵活反应的能力。
