Clarification of Plant Octadecanoide Signaling Pathway by using the Modified Probe of Phytotoxin, Coronatine

冠菌素是一种植物毒素，在内源植物激素类调节剂十八烷基内酯/茉莉酸内酯的诱导下具有多种生物活性。由于冠菌素引起的生物活性强度高于十八烷酸/茉莉素，因此冠菌素似乎是阐明植物十八烷酸信号转导途径的最有价值的探针。利用催化不对称合成技术，可以在1-2g的范围内合成冠花碱的酸性成分冠醚。冠麻酸部分结构的修饰(共轭双键和/或羰基的还原)使得提供化学稳定的冠状类似物成为可能，这些冠状类似物具有不同的探针部分(荧光发色团、光亲和标记官能团、放射性元素和生物素)。由于冠花酸中引入了连接体，使得冠状类似物亲和层析的制备成为可能。合成的冠状类似物用水稻叶片进行生物测定。用冠菌素类似物溶液处理水稻叶片6h后，对叶片顶空诱导挥发物(萜烯)进行了定量分析。大部分冠状类似物表现出比外消旋茉莉酸更强的挥发性诱导活性，而外消旋茉莉酸则作为阳性对照。部分冠状类似物的活性高于冠状本身。因此，这些结果表明冠菌素类似物可能是阐明冠菌素结合蛋白的有用的化学探针，该蛋白可能是参与植物十八烷酸信号转导途径的十八烷基醚/茉莉酸结合蛋白。冠菌素结合蛋白的测定研究目前正在进行中。

A phytotoxin, coronatine exhibits various biological activities induced by endogenous phytohormone-like regulators, octadecanoide/jasmonoide. Because the intensity of biological activity caused by coronatine is higher than those by octadecanoide/jasmonoide, it seems that coronatine is the most valuable probe to clarify plant octadecanoide signaling pathway.Coronafacic acid, the acid component of coranatine could be synthesized in 1-2 g scale by using the catalytic asymmetric synthesis. The modification of partial structure of coronafacic acid (reduction of conjugated double bond and/or carbonyl group) made it possible to provide chemically stable coronatine analogs, which possess various probe parts (fluorescent chromophore, photoaffinity labeling functional group, radioactive element, and biotin). Since the introduction of a linker to the coronamic acid, was achived, preparation of the affinity chromatography linked by coronatine analogs is possible.The synthesized coronatine analogs were subjected to the bioassay using rice leaves. After treatment of rice leaves with solution of coronatine analogs for 6 h, induced volatiles (terpenes) from leaves to headspace were quantitatively analyzed. Most of the coronatine analogs exhibited higher volatile-inducing activity than that caused by racemic jasmonic acid, which was used as the positive control in this assay. The activity of some coronatine analogs was higher than that of coronatine itself. Therefore, these results showed that coronatine analogs would be useful chemical probes to clarify coronatine binding protein, which might be octadecanoide/jasmonoide binding protein responsible for plant octadecanoide signaling pathway.The research on determination of coronatine binding protein is now in progress.