ciszeatin

Cis-zeatin, abbreviated cZ, is a natural plant cytokinin and an isomer of zeatin in which the side-chain configuration is cis rather than trans. It belongs to the cytokinin family, a class of purine derivatives that regulate cell division, shoot initiation, leaf senescence, nutrient distribution, and other developmental processes in plants.

Occurrence and biosynthesis: Cis-zeatin has been detected in a wide range of plant species, including crops and ornamental plants. In many higher plants, trans-zeatin is more abundant, while cis-zeatin can make up a substantial portion of the cytokinin pool in certain tissues or species. The biosynthesis of cis-zeatin is less well understood than that of trans-zeatin; it is commonly associated with the turnover of cis-zeatin-containing tRNA, though de novo formation of cis-zeatin has been reported in some contexts. Like other cytokinins, cis-zeatin is subject to metabolic regulation by cytokinin oxidases/dehydrogenases and can be conjugated to nucleotides or glucose, which modulates its activity and transport.

Transport and activity: Cytokinins are transported through the plant via xylem and phloem networks, and cis-zeatin can be biologically active, though its potency and receptor affinity are generally lower than those of trans-zeatin in many systems. Receptors such as Arabidopsis thaliana AHK2, AHK3, and CRE1/AHK4 can respond to cis-zeatin, with responses that can be tissue- and species-specific.

Biological and research relevance: Cis-zeatin is routinely detected by analytical methods such as LC-MS in plant tissues. Its precise physiological roles and its relative importance compared with trans-zeatin vary by species and tissue, making it an ongoing area of cytokinin research.