Rissland I, Mohr H
Botanisches Institut der Universität Freiburg i. Br., Freiburg i. Br, Deutschland.
Planta. 1967 Sep;77(3):239-49. doi: 10.1007/BF00385294.
In previous papers we have reported (MOHR and DURST, 1966a, b) that synthesis of phenylalanine deaminase (EC 4.3.1.5), an important enzyme of phenolic metabolism, can be stimulated by the physiologically active phytochrome (=P730) in the mustard seedling. The data of the present paper suggest that induction of this enzyme is a rapid process if the gene in question is easily accessible for the activating action of P730.The seedlings were irradiated with continuous standard far-red light. Longtime irradiation with far-red will maintain a low but virtually constant level of P730 in the seedling over an extended period of time. At the moment when the far-red light is turned off the action of P730 will virtually cease. - Fig. 3 and Fig. 4, lower part, show the kinetics of enzyme induction by P730 in an etiolated seedling. The initial (or primary) lag-phase after the onset of far-red is 1.5 hours. If, however, a seedling which has been pre-irradiated with 12 hours of far-red is kept in darkness for 6 hours and is then re-irradiated with far-red no lag-phase for the action of the second irradiation can be found. Enzyme activity increases immediately after the onset of far-red. Since the action of the second irradiation as measured by increase of enzyme activity can be inhibited by relatively low doses of Puromycin and Cycloheximide (table) we conclude that the re-appearance of P730 leads to de novo synthesis of enzyme protein. - Application of Actinomycin D (10 μg/ml) only partially inhibits the action of the second irradiation as measured by increase of enzyme activity. This finding was to be expected. In preceding papers (e.g. MOHR and BIENGER, 1967) it has been concluded that genes which have once been activated by P730 remain less sensitive towards Actinomycin D even when P730 has disappeared. Taking into account all available data the conclusion seems to be justified that the induction of enzyme synthesis by P730 (i.e. differential gene activation followed by enzyme synthesis) is a rapid process if the genes are accessible for the action of P730. The relatively long initial lag-phase (1.5 hours) is needed to make the "potentially active genes (P730)" accessible for the action of P730. The problem of how the initial lag-phase can be understood has been dealt with more in detail in a previous paper on phytochrome-mediated anthocyanin synthesis (LANGE, BIENGER and MOHR, 1967).
在之前的论文中我们已经报道过（莫尔和德斯特，1966a，b），苯丙氨酸脱氨酶（EC 4.3.1.5）是酚类代谢中的一种重要酶，其合成在芥菜幼苗中可被生理活性的光敏色素（=P730）所刺激。本文的数据表明，如果所讨论的基因易于受到P730的激活作用影响，那么这种酶的诱导是一个快速过程。幼苗用连续的标准远红光照射。长时间用远红光照射会在较长一段时间内使幼苗中P730维持在一个低但几乎恒定的水平。当远红光关闭时，P730的作用实际上就会停止。——图3和图4的下半部分显示了在黄化幼苗中P730诱导酶的动力学过程。远红光开始后的初始（或初级）延迟期为1.5小时。然而，如果一株预先用12小时远红光照射过的幼苗在黑暗中放置6小时，然后再用远红光照射，第二次照射的作用不会出现延迟期。远红光开始后酶活性立即增加。由于用嘌呤霉素和环己酰亚胺的相对低剂量就能抑制以酶活性增加来衡量的第二次照射的作用（表），我们得出结论，P730的重新出现导致了酶蛋白的从头合成。——用放线菌素D（10微克/毫升）处理仅部分抑制了以酶活性增加来衡量的第二次照射的作用。这一发现是可以预料到的。在之前的论文中（例如莫尔和宾格，1967）已经得出结论，一旦被P730激活的基因，即使P730消失了，对放线菌素D仍保持较低的敏感性。考虑到所有现有数据，似乎有理由得出这样的结论：如果基因易于受到P730的作用影响，那么P730诱导酶合成（即差异基因激活随后进行酶合成）是一个快速过程。需要相对较长的初始延迟期（1.5小时）才能使“潜在活性基因（P730）”易于受到P730的作用影响。关于如何理解初始延迟期的问题，在之前一篇关于光敏色素介导的花青素合成的论文中（兰格、宾格和莫尔，1967）已经有更详细的论述。
