Institute for Photobiology of Cells and Organelles, Brandeis University, Waltham, Massachusetts.
Plant Physiol. 1976 Feb;57(2):260-9. doi: 10.1104/pp.57.2.260.
The herbicide SAN 9789 (4-chloro-5-(methylamino)-2-(alpha,alpha,alpha-trifluoro-m-tolyl-3- (2H)pyridazinone) blocks carotenoid synthesis in growing and resting cells of Euglena at concentrations of 20 to 100 mug/ml without affecting cell viability. Although the inhibition is immediate and complete, in resting cells no decrease in already synthesized carotenoids is found indicating a lack of turnover. In cells growing in the dark, carotenoids are diluted out as the cells divide. Cells dividing in the light in the presence of SAN 9789, eventually lose viability, presumably because of photooxidations usually prevented by carotenoids. During 72 hours of light-induced plastid development in dark-grown resting cells, none of the usual carotenoids increase while phytoene accumulates, indicating that SAN 9789 blocks carotenoid synthesis at this point. Chlorophyll synthesis and membrane formation are also blocked by the herbicide, but these inhibitions appear to be secondary to the inhibition of carotenoid synthesis. That carotenoid levels are strongly correlated with and may control the synthesis of chlorophyll and the formation of plastid membranes is suggested by the following data. (a) If dark-grown dividing cells are placed in the presence of the herbicide for various periods, rested and exposed to light in the presence of the drug, different amounts of carotenoids remain in the cells and the amount of chlorophyll finally synthesized is proportional to the amount of carotenoids present. (b) Photodestruction of chlorophyll is excluded, since the same amounts of chlorophyll are formed at intensities of 10 to 100 foot-candles of light. (c) Photoconversion of protochlorophyll(ide) to chlorophyll(ide) in dark-grown cells is not blocked by the herbicide. (d) Initial rates of chlorophyll synthesis are the same in treated and nontreated cells. (e) The extent of membrane formation appears to parallel the amount of carotenoids present as judged by electron microscopy.
除草剂 SAN 9789（4-氯-5-（甲氨基）-2-（α，α，α-三氟-间-甲苯-3-（2H）哒嗪酮））以 20 至 100 微克/毫升的浓度阻断在生长和静止的衣藻细胞中的类胡萝卜素合成，而不影响细胞活力。尽管抑制作用是立即和完全的，但在静止细胞中，已经合成的类胡萝卜素没有减少，表明没有周转。在黑暗中生长的细胞中，随着细胞分裂，类胡萝卜素被稀释掉。在有 SAN 9789 的情况下，在光下分裂的细胞最终失去活力，可能是因为类胡萝卜素通常防止了光氧化。在黑暗中生长的静止细胞中进行 72 小时的光诱导质体发育期间，虽然phytoene 积累，但通常的类胡萝卜素没有增加，表明 SAN 9789 在这一点上阻断了类胡萝卜素的合成。叶绿素合成和膜形成也被除草剂阻断，但这些抑制作用似乎是类胡萝卜素合成抑制的继发反应。以下数据表明，类胡萝卜素水平与叶绿素合成和质体膜形成密切相关，可能控制着它们的合成。(a) 如果将黑暗中生长的分裂细胞在除草剂存在下放置不同的时间，然后在药物存在下休息并暴露在光下，细胞中残留的类胡萝卜素量不同，最终合成的叶绿素量与存在的类胡萝卜素量成正比。(b) 排除了光对叶绿素的破坏，因为在 10 到 100 英尺烛光的光强度下，形成的叶绿素量相同。(c) 除草剂不阻断黑暗中生长的细胞中原叶绿素（ide）向叶绿素（ide）的光转化。(d) 用和不用除草剂处理的细胞的初始叶绿素合成速率相同。(e) 根据电子显微镜观察，膜形成的程度似乎与存在的类胡萝卜素量平行。
