Regulation of Nuclear Enzymes by Phytochrome

本研究旨在确定植物色素蛋白光敏色素对核酶活性，特别是染色质相关核苷三磷酸酶(NTPase)活性的可逆性调节机制。这项研究是为了跟踪和推广早期的发现，即红光激活的光敏色素可以刺激豌豆核中NTPase的活性和核蛋白的磷酸化，而钙和钙调蛋白在这一反应中起着重要的作用。这将确定需要多少钙离子来支持ı的刺激，并确定红光是否会引起游离NTPase钙离子的变化！在核准备过程中。光敏色素将被免疫细胞化学定位在分离的细胞核中，以帮助评估它在制剂中可能发挥作用的位置。纯化的NTPase与DNA的结合将被研究。将寻找被该酶识别的特定DNA序列。有证据表明，NTPase可能被精胺激活的NiI激酶磷酸化。我们将分离并鉴定这种激酶，以测试它是否能磷酸化NTPase，以及钙是否也能促进它的激活。%从拟议的实验中预期的结果将大大有助于更好地理解光和钙离子如何调节核代谢，这也可能对光敏色素如何调节基因表达的模型产生影响。这个项目的最终目的是了解植物的光感受器光敏色素是如何控制植物的生长和发育变化的。目前的数据支持这样一种假设，即在许多情况下，光敏色素通过诱导靶细胞膜特性的特定变化来实现这种控制。

This research seeks to determine the mechanisms by which the plant chromoprotein, phytochrome, photoreversibly regulates the activity of nuclear enzymes, especially that of a chromatin-associated nucleoside triphosphatase (NTPase). The research is designed to follow up and extend earlier findings which showed that red-light activated phytochrome could stimulate NTPase activity and nuclear protein phosphorylation in isolated pea nuclei and that Ca2+ and calmodulin played important roles in this response. It will be determined how much Ca2+ is required to support the NTPase stimulation and determine whether red light induces a change in the free ıCa2+! in the nuclear preparation. Phytochrome will be immunocytochemically localized in isolated nuclei to help evaluate where within the preparation it may be functioning. Binding of purified NTPase to DNA will be studied. Specific DNA sequences that are recognized by the enzyme will be sought. There is evidence the NTPase may be phosphorylated by a spermine-activated NII kinase. This kinase will be isolated and characterized to test whether it can phosphorylate the NTPase and whether its activation is promoted also by calcium.%%% Results expected from the proposed experiments should contribute significantly to an improved understanding of how light and Ca2+ can regulate nuclear metabolism, with possible implications also for models of how phytochrome regulates gene expression. The ultimate aim of this project is to understand how the plant photoreceptor, phytochrome, controls growth and development changes in plants. Current data favor the hypothesis that phytochrome achieves this control in many instances by inducing specific alterations of membrane properties in target cells.***//