Disease relevance of kinetin

• The rolC gene of Agrobacterium rhizogenes, which drastically affects growth and development of transgenic plants, codes for a cytokinin-beta-glucosidase [1].
• Indeed, rolC protein expressed in Escherichia coli as a fusion protein hydrolyses cytokinin glucosides, thus liberating free cytokinins [1].
• Fasciation induction by the phytopathogen Rhodococcus fascians depends upon a linear plasmid encoding a cytokinin synthase gene [2].
• Mutant seeds had more rapid germination, reduced requirement for light, and decreased far-red light sensitivity, unraveling cytokinin functions in seed germination control [3].
• It also exhibits less sensitivity to auxin and cytokinin and hypersensitivity to abscisic acid (ABA) [4].

High impact information on kinetin

• The role of ms2io6-adenine (the cytokinin hormone in plants) and i6-adenine (an activator of the cell cycle in animal cells) is discussed as related to the role of modifying enzymes in regulation [5].
• Ectopic expression in transgenic Arabidopsis of ARR2, the rate-limiting factor in the response to cytokinin, is sufficient to mimic cytokinin in promoting shoot meristem proliferation and leaf differentiation, and in delaying leaf senescence [6].
• Identification of CRE1 as a cytokinin receptor from Arabidopsis [7].
• Two-component circuitry in Arabidopsis cytokinin signal transduction [6].
• CRE1 expression conferred a cytokinin-dependent growth phenotype on a yeast mutant that lacked the endogenous histidine kinase SLN1 (ref. 10), providing direct evidence that CRE1 is a cytokinin receptor [7].

Chemical compound and disease context of kinetin

• Oncogenes carried by the transferred DNA (T-DNA) of Agrobacterium Ti plasmids encode the synthesis of plant growth factors, auxin and cytokinin, and induce tumour development in plants [8].
• This zeatin resistance was associated with a hypertrophy of mutant cotyledons in response to cytokinin [9].
• The class 2 haemoglobin gene (GLB2) is expressed in the roots, leaves and inflorescence and can be induced in young plants by cytokinin treatment in contrast to the class 1 gene (GLB1) which is active in germinating seedlings and can be induced by hypoxia and increased sucrose supply, but not by cytokinin treatment [10].
• Hydroxylated cytokinin, 2-methylthio-N6-(4-hydroxy-3-methylbut-2-enyl) adenosine, was found in the tRNA of Azotobacter vinelandii [11].
• 4-Hydroxyphenethyl alcohol--a new cytokinin-like substance from the phototrophic purple bacterium Rhodospirillum rubrum 1R [12].

Biological context of kinetin

• Constitutive expression of CycD3 in transgenic plants allowed induction and maintenance of cell division in the absence of exogenous cytokinin [13].
• The understanding of the function of these response regulator genes is only rudimentary but the transcriptional induction of a subset by cytokinin suggests a role for some of these regulators in the response to this important plant hormone [14].
• Gene 4 from the T-region of Ti plasmids is responsible for cytokinin effects in crown gall cells; we investigated whether it codes for an enzyme of hormone biosynthesis [15].
• Spatial patterns of ARR gene expression were consistent with partially redundant function of these genes in cytokinin signaling [16].
• In addition, we have crystallized this cytokinin-specific binding protein (Vr CSBP) in complex with zeatin and refined the structure to 1.2 A resolution [17].

Anatomical context of kinetin

• The ability of protoplasts to sustain growth in response to cytokinin glucosides persisted indefinitely after the likely disappearance of the expression vector [18].
• Different AtCKX-green fluorescent protein fusion proteins were localized to the vacuoles or the endoplasmic reticulum and possibly to the extracellular space, indicating that subcellular compartmentation plays an important role in cytokinin biology [19].
• Agrobacterium tumefaciens increases cytokinin production in plastids by modifying the biosynthetic pathway in the host plant [20].
• These results indicate that Ca2+ is taken up into moss protoplasts through voltage-dependent DHP-sensitive Ca2+ channels on the plasma membrane and that one of the cytokinin effects in the induction of bud formation is regulation of this plasma membrane Ca2+ channel [21].
• These results suggest that cytokinin may exert control of cell division through the accumulation of molecules (the dehydrodiconiferyl glucosides) that are apparent cell wall components [22].

Associations of kinetin with other chemical compounds

• 5'-AMP is a direct precursor of cytokinin in Dictyostelium discoideum [23].
• The prl1 mutation also augments the sensitivity of plants to growth hormones including cytokinin, ethylene, abscisic acid, and auxin; stimulates the accumulation of sugars and starch in leaves; and inhibits root elongation [24].
• The domain is predicted to bind diverse low molecular weight ligands, such as the cytokinin-like adenine derivatives or peptides, and mediate signal transduction through the respective receptors [25].
• The Arabidopsis histidine phosphotransfer proteins are redundant positive regulators of cytokinin signaling [26].
• Expression of POLARIS is inducible by exogenous auxin and suppressed by cytokinin but is unaffected by inhibitors of polar auxin transport or cell division [27].

Gene context of kinetin

• Application of exogenous cytokinins to the resultant strains revealed that both AHK2 and AHK3 function as positive regulators for cytokinin signaling similar to AHK4 [28].
• Together, the analyses reveal partially redundant functions of the cytokinin receptors and prominent roles for the AHK2/AHK3 receptor combination in quantitative control of organ growth in plants, with opposite regulatory functions in roots and shoots [3].
• In a similar manner, cytokinin treatment increased the stability of ACS5 by a mechanism that is at least partially independent of the eto2 mutation [29].
• Constitutive overexpression of UGT76C1 in transgenic Arabidopsis confirmed that the recombinant enzyme functioned in vivo to glucosylate cytokinin applied to the plant [30].
• Among the plant hormones tested, cytokinin significantly downregulated the expression of SULTR1;2 [31].
• Microarray analysis revealed that expression of the majority of cytokinin-regulated genes requires the function of ARR1, ARR10, and ARR12 [32].

Analytical, diagnostic and therapeutic context of kinetin

• The D-type cyclin CycD3 was found to be elevated in a mutant of Arabidopsis with a high level of cytokinin and to be rapidly induced by cytokinin application in both cell cultures and whole plants [13].
• However, analogs of cytokinin that are much less active in bioassays induce lower levels of message accumulation [33].
• Characterization of a benzyladenine binding-site peptide isolated from a wheat cytokinin-binding protein: sequence analysis and identification of a single affinity-labeled histidine residue by mass spectrometry [34].
• Guard cell [Ca2+]cyt increased, whereas pHcyt decreased after treatment of closed stomata with IAA, kinetin, or FC [35].
• We identified a set of cytokinin-insensitive mutants by using a screen based on the ethylene-mediated triple response observed after treatment with low levels of cytokinins [36].

References