zeatine

Zeatine is a plant cytokinin, a class of plant hormones that regulate cell division and various developmental processes. In many sources the spelling zeatine appears as an older or alternative form of zeatin; in current nomenclature, zeatin (including its derivatives) is the preferred term. The natural forms most commonly recognized are trans-zeatin and cis-zeatin, both of which are purine derivatives with an isoprenoid side chain attached at the N6 position of the adenine ring. Zeatin also exists as ribosides, such as zeatin riboside, and as related phosphate esters.

Occurrence and distribution: Zeatin is widely distributed in vascular plants and has been detected in a range of tissues, including seeds, meristems, and xylem exudates. It is particularly associated with monocots like maize and is found in various plant exudates and tissues where active cell division and growth occur.

Biogenesis and metabolism: Zeatin biosynthesis involves the isoprenoid pathway. Enzymes called isopentenyltransferases initially generate isopentenyladenine nucleotides, which can be hydroxylated to form zeatin-type cytokinins. Zeatin can be interconverted with riboside and phosphate forms and is inactivated or recycled by conjugation to sugars or oxidation, shaping its active pool in tissues.

Biological role and applications: As a cytokinin, zeatin stimulates cell division, influences shoot initiation and development, and can delay leaf senescence. In plant tissue culture, zeatin and its derivatives are routinely used to promote shoot regeneration and to direct organogenesis in combination with auxins. The activity of zeatin depends on its isomer (trans vs. cis) and the concentration employed.

See also: cytokinins; zeatin riboside.