2016 年 51 巻 1 号 p. 24-29
Plants maximize fitness by coordinating growth and development of cells as well as organs in response to environmental changes. For the coordination, cell-to-cell and long-distance communication among cells and organs is necessary. Cytokinins, a class of phytohormones that play key roles in various processes of plant growth and development, have been implicated in the communication. It has been shown that cytokinin action is regulated at various steps, including de novo biosynthesis, degradation, transport, perception, and signaling, to play roles in the communication. This review summarizes and provides updates on the regulatory mechanisms of cytokinin action with major emphasis on cytokinin de novo biosynthesis and transport. We also introduce the mechanisms of cytokinin biosynthesis by phytopathogens that exploit cytokinin action for their infection.