Biological Institute II, University of Freiburg, Schaenzlestrasse 1, D-78 Freiburg i.Br., Federal Republic of Germany.
Proc Natl Acad Sci U S A. 1985 Sep;82(18):6124-8. doi: 10.1073/pnas.82.18.6124.
Anthocyanin formation in milo (Sorghum vulgare Pers.) seedlings (coleoptile, mesocotyl, taproot) occurs only in white light and blue/UV light (BL/UV), while red light (RL) and far-RL are totally ineffective. However, after a BL/UV pretreatment, the participation of phytochrome can be demonstrated. With a short-wavelength light source [peak emission in longwave UV (UV-A)], the mode of coaction between BL/UV and light absorbed by phytochrome (RL) was studied with the following principal results. (i) As soon as the seedling becomes competent to respond to UV-A (with regard to anthocyanin formation), the involvement of phytochrome can be detected. (ii) A 5-min pulse of UV-A has a strong effect on the anthocyanin synthesis in the milo mesocotyl. This effect is fully reversible if a long-wavelength far-RL pulse (RG9 light) is given immediately after the UV-A light pulse. (iii) When seedlings treated with 5 min of UV-A and 5 min of RG9 light are kept in darkness for 3 hr and then transferred to RL, anthocyanin appears. (iv) In continuous UV-A treatment, anthocyanin accumulation starts after a lag phase of 3.5 hr (25 degrees C). A RL pretreatment prior to the onset of UV-A treatment strongly increases anthocyanin accumulation in UV-A, though the lag phase is not affected. Moreover, a RL pretreatment does not affect the time course for escape from reversibility in UV-A. It is concluded from these data that BL/UV cannot mediate induction of anthocyanin synthesis in the absence of P(fr), the active form of phytochrome that absorbs maximally in the far-red. Rather, the action of BL/UV must be considered to establish responsiveness of the anthocyanin-producing mechanism to P(fr). P(fr) operates in this system via two different channels. As the effector of the terminal response, it sets in motion the signal-response chain that eventually leads to the appearance of anthocyanin. This is a slow process with a lag phase of the order of 3.5 hr. The second function of P(fr) is to determine the responsiveness to the effector P(fr) in mediating anthocyanin synthesis. This is a very fast and highly sensitive phytochrome action that can be detected readily within 1 min. However, as long as the plant has not received BL/UV, the strong effect of RL on the effectiveness of P(fr) remains cryptic. The effect of a RL pretreatment and the effect of a UV-A pretreatment on responsiveness towards P(fr) (or, effectiveness of P(fr)) were found to be totally independent of each other, even though it is the UV-A that permits operation of P(fr).
高粱幼苗（芽鞘、中胚轴、主根）中的花色素苷形成仅发生在白光和蓝/紫外光（BL/UV）下，而红光（RL）和远 RL 则完全无效。然而，在 BL/UV 预处理后，可以证明植物色素的参与。使用短波长光源[长波紫外线（UV-A）的峰值发射]，研究了 BL/UV 与植物色素吸收的光（RL）之间的协同作用模式，主要结果如下。（i）一旦幼苗对 UV-A（关于花色素苷形成）有反应能力，就可以检测到植物色素的参与。（ii）5 分钟的 UV-A 脉冲对高粱中胚轴的花色素苷合成有很强的影响。如果在 UV-A 光脉冲后立即给予长波长远 RL 脉冲（RG9 光），则该影响是完全可逆的。（iii）用 5 分钟的 UV-A 和 5 分钟的 RG9 光处理的幼苗在黑暗中放置 3 小时，然后转移到 RL 下，花色素苷出现。（iv）在连续的 UV-A 处理中，花色素苷积累在 25°C 时的滞后阶段 3.5 小时后开始。在 UV-A 处理开始之前进行 RL 预处理会强烈增加 UV-A 中的花色素苷积累，尽管滞后阶段不受影响。此外，RL 预处理不会影响从 UV-A 中恢复的可逆性的时间进程。从这些数据得出的结论是，BL/UV 不能在没有 P（fr）的情况下介导花色素苷合成的诱导，P（fr）是吸收最大值在远红区的植物色素的活性形式。相反，BL/UV 的作用必须被认为是建立花色素苷产生机制对 P（fr）的反应性。P（fr）在该系统中通过两个不同的通道发挥作用。作为末端反应的效应物，它启动了信号反应链，最终导致花色素苷的出现。这是一个具有 3.5 小时左右的滞后阶段的缓慢过程。P（fr）的第二个功能是确定 P（fr）在介导花色素苷合成中的反应性。这是一个非常快速和高度敏感的植物色素作用，可以在 1 分钟内轻松检测到。然而，只要植物尚未接收到 BL/UV，RL 对 P（fr）有效性的强烈影响仍然是隐藏的。RL 预处理和 UV-A 预处理对 P（fr）（或 P（fr）的有效性）的反应性的影响彼此完全独立，尽管正是 UV-A 允许 P（fr）发挥作用。
