Organ-to-organ signal transmission is essential for higher organisms to ensure coordinated biological reactions during metabolism and morphogenesis. Similar to organs in animals, plant organs communicate by various signalling molecules. Among them, cytokinins, a class of phytohormones, play a key role as root-to-shoot long-distance signals, regulating various growth and developmental processes in shoots^1,2. Previous studies have proposed that trans-zeatin-riboside, a type of cytokinin precursor, is a major long-distance signalling form in xylem vessels and its action depends on metabolic conversion via the LONELY GUY enzyme in proximity to the site of action^3-5. Here we report an additional long-distance signalling form of cytokinin: trans-zeatin, an active form. Grafting between various cytokinin biosynthetic and transportation mutants revealed that root-to-shoot translocation of trans-zeatin, a minor component of xylem cytokinin, controls leaf size but not meristem activity-related traits, whereas that of trans-zeatin riboside is sufficient for regulating both traits. Considering the ratio of trans-zeatin to trans-zeatin-riboside in xylem and their delivery rate change in response to environmental conditions, this dual long-distance cytokinin signalling system allows plants to fine-tune the manner of shoot growth to adapt to fluctuating environments.

中文翻译：

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反式玉米蛋白及其前体的系统转运在拟南芥芽中具有不同的作用。

器官间的信号传递对于高级生物至关重要，以确保新陈代谢和形态发生过程中协调一致的生物反应。类似于动物的器官，植物器官通过各种信号分子进行通讯。其中，细胞分裂素，一类植物激素，起着根部射击远距离信号的作用，调节芽^1,2中的各种生长和发育过程。先前的研究提出，一种细胞分裂素前体反式玉米素-核糖体是木质部血管中的主要长途信号传导形式，其作用取决于在作用部位^3-5附近通过LONELY GUY酶的代谢转化。。在这里，我们报告了细胞分裂素的另一种长途信号传导形式：反式玉米素，一种活性形式。各种细胞分裂素生物合成和运输突变体之间的嫁接显示，木质素细胞分裂素的次要组成部分反式玉米素的根到茎易位，可控制叶片大小，但不控制分生组织活性相关性状，而反式玉米素核糖体足以调节两种特质。考虑到木质素中反玉米蛋白与反玉米蛋白核苷的比例及其响应环境条件的传递速率变化，这种双重长距离细胞分裂素信号传导系统使植物可以微调枝条的生长方式，以适应不断变化的环境。