The Hulks and the Deadpools of the Cytokinin Universe: A Dual Strategy for Cytokinin Production, Translocation, and Signal Transduction.

Cytokinins are plant hormones, derivatives of adenine with a side chain at the -position. They are involved in many physiological processes. While the metabolism of -zeatin and isopentenyladenine, which are considered to be highly active cytokinins, has been extensively studied, there are others with less obvious functions, such as -zeatin, dihydrozeatin, and aromatic cytokinins, which have been comparatively neglected.

Cytokinin -glucosides: Occurrence, Metabolism and Biological Activities in Plants.

Cytokinins (CKs) are a class of phytohormones affecting many aspects of plant growth and development. In the complex process of CK homeostasis in plants, -glucosylation represents one of the essential metabolic pathways. Its products, CK 7- and 9-glucosides, have been largely overlooked in the past as irreversible and inactive CK products lacking any relevant physiological impact.

Characterization of five CHASE-containing histidine kinase receptors from Populus × canadensis cv. Robusta sensing isoprenoid and aromatic cytokinins.

Five poplar CHASE-containing histidine kinase receptors bind cytokinins and display kinase activities. Both endogenous isoprenoid and aromatic cytokinins bind to the receptors in live cell assays. Cytokinins are phytohormones that play key roles in various developmental processes in plants.

Occurrence and biosynthesis of cytokinins in poplar.

Isoprenoid and aromatic cytokinins occur in poplar as free compounds and constituents of tRNA, poplar isopentenyltransferases are involved in the production of isoprenoid cytokinins, while biosynthesis of their aromatic counterparts remains unsolved. Cytokinins are phytohormones with a fundamental role in the regulation of plant growth and development. They occur naturally either as isoprenoid or aromatic derivatives, but the latter are quite rare and less studied.

The Cytokinin Oxidase/Dehydrogenase CKX1 Is a Membrane-Bound Protein Requiring Homooligomerization in the Endoplasmic Reticulum for Its Cellular Activity.

Degradation of the plant hormone cytokinin is controlled by cytokinin oxidase/dehydrogenase (CKX) enzymes. The molecular and cellular behavior of these proteins is still largely unknown. In this study, we show that CKX1 is a type II single-pass membrane protein that localizes predominantly to the endoplasmic reticulum (ER) in Arabidopsis ().

Purification of Maize Nucleotide Pyrophosphatase/Phosphodiesterase Casts Doubt on the Existence of Zeatin - Isomerase in Plants.

Almost 25 years ago, an enzyme named zeatin isomerase from common bean has been described by Bassil et al. (1993). The partially purified enzyme required an external addition of FAD and dithiothreitol for the conversion of -zeatin to its isomer that occurred only under light.

Cytokinin metabolism in maize: Novel evidence of cytokinin abundance, interconversions and formation of a new trans-zeatin metabolic product with a weak anticytokinin activity.

Cytokinins (CKs) are an important group of phytohormones. Their tightly regulated and balanced levels are essential for proper cell division and plant organ development. Here we report precise quantification of CK metabolites and other phytohormones in maize reproductive organs in the course of pollination and kernel maturation.

Evolution of cytokinin biosynthesis and degradation.

Cytokinin hormones are important regulators of development and environmental responses of plants that execute their action via the molecular machinery of signal perception and transduction. The limiting step of the whole process is the availability of the hormone in suitable concentrations in the right place and at the right time to interact with the specific receptor. Hence, the hormone concentrations in individual tissues, cells, and organelles must be properly maintained by biosynthetic and metabolic enzymes.

Vacuolar and cytosolic cytokinin dehydrogenases of Arabidopsis thaliana: heterologous expression, purification and properties.

The catabolism of cytokinins is a vital component of hormonal regulation, contributing to the control of active forms of cytokinins and their cellular distribution. The enzyme catalyzing the irreversible cleavage of N(6)-side chains from cytokinins is a flavoprotein classified as cytokinin dehydrogenase (CKX, EC 1.5.

Characterization of new maize genes putatively involved in cytokinin metabolism and their expression during osmotic stress in relation to cytokinin levels.

Plant hormones, cytokinins (CKs), have been for a long time considered to be involved in plant responses to stress. However, their exact roles in processes linked to stress signalization and acclimatization to adverse environmental conditions are unknown. In this study, expression profiles of the entire gene families of CK biosynthetic and degradation genes in maize (Zea mays) during development and stress responses are described.