Cytokinin biosynthesis and perception

Cytokinin has been considered to be a master regulator of plant growth and development, but only in the past several years has substantial progress been made uncovering the roles of cytokinins at various developmental stages. Recent studies on key metabolic enzymes and signaling components have contributed to understanding the basic mechanism of biosynthesis and perception of cytokinin within a whole plant body. The initial products of de novo cytokinin biosynthesis in higher plants and Agrobacterium are different, and the regulatory systems in biosynthesis and homeostasis are finely controlled and appear to be important in communicating nutrient signals to morphogenetic responses. The cytokinin receptors have largely overlapping, but still specific, functions in diverse cytokinin responses. In this review, we will specifically emphasize the biosynthesis of isoprenoid cytokinins and perception of cytokinin signals in Arabidopsis.