https://emsenn.net/tags/celldivision/ Recent content in CellDivision on emsenn.net Hugo en-us Thu, 02 Apr 2026 00:00:00 +0000 https://emsenn.net/library/domains/science/domains/biology/domains/botany/terms/cytokinin/ Thu, 02 Apr 2026 00:00:00 +0000 https://emsenn.net/library/domains/science/domains/biology/domains/botany/terms/cytokinin/ <p>Cytokinin: a class of plant hormones that promote cell division (cytokinesis) and delay senescence (leaf aging). Synthesized primarily in root tips, transported upward in the xylem, and perceived through a two-component phosphorelay system. The name derives from their role in cytokinesis, though their regulatory functions extend far beyond cell division.</p> <h2 id="biosynthesis-and-activation">Biosynthesis and activation</h2> <p>The rate-limiting step in cytokinin synthesis is catalyzed by isopentenyltransferase (IPT) enzymes, which transfer an isopentenyl group from dimethylallyl diphosphate (DMAPP) to adenine nucleotides, forming isopentenyl adenine (iP)-type cytokinins. CYP735A cytochrome P450 enzymes then convert these to the trans-zeatin (tZ) types, which are typically more bioactive. Inactive cytokinin nucleotides are converted to bioactive free bases by LONELY GUY (LOG) phosphoribohydrolases. The active forms — isopentenyl adenosine, zeatin, and zeatin riboside — are perceived by the plant&rsquo;s sensory machinery.</p>