transzeatin

Trans-zeatin, abbreviated trans-zeatin (tZ), is a natural plant hormone belonging to the cytokinin family. It is a purine derivative with an isoprenoid side chain and occurs in two geometric isomers, with the trans form typically being more abundant and often more biologically active in many species. Trans-zeatin is widely distributed in vascular plants and has been detected in tissues such as roots, shoots, seeds, and in xylem sap, from which it can be transported to sites of growth and development.

Biosynthesis and metabolism of trans-zeatin involve multiple pathways. It can arise from de novo cytokinin biosynthesis, where adenosine phosphate isopentenyltransferases generate isopentenyladenine-type cytokinins that may be hydroxylated by specific enzymes to form trans-zeatin. Trans-zeatin can also originate from tRNA-dependent pathways and be released during tRNA turnover. Regulation of trans-zeatin levels is mediated by cytokinin oxidases/dehydrogenases (CKXs), which degrade cytokinins, as well as by conjugation or glycosylation that modulates activity and storage.

Functions of trans-zeatin include promoting cell division and differentiation, stimulating shoot initiation and organogenesis, and delaying leaf senescence by maintaining chlorophyll content and nutrient remobilization. Cytokinins interact with other hormones, notably auxin, to influence apical dominance, branching, and the balance between root and shoot growth. In plants, cytokinins are often transported in the xylem as riboside forms and can be converted to active free bases in target tissues.

Applications of trans-zeatin encompass plant biotechnology and horticulture, where exogenous cytokinins are used to enhance in vitro propagation, shoot formation, and stock plant vigor. The study of trans-zeatin contributes to the broader understanding of cytokinin signaling pathways, receptor interactions, and the regulation of growth and senescence in plants.