Cytokinin affects the requirement for auxin of a strain of tobacco callus (Nicotiana tabacum) which is cytokinin-autotrophic when grown on Murashige and Skoog medium with 11.4 mum of indole-3-acetic acid but requires cytokinin 6-(3-methyl-2-butenylamino)purine (i(6) Ade) when grown on the same medium with <3 mum indole-3-acetic acid. As the exogenous concentration of cytokinin (i(6) Ade) is inc...

Cytokinins have been implicated in normal plant growth and development. These bioactive molecules are essential for cell production and expansion in higher plants. Carrot is an Apiaceae vegetable with great value and undergoes significant size changes over the process of plant growth. However, cytokinin accumulation and its potential roles in carrot growth have not been elucidated. To address t...

Cytokinins play critical roles in plant growth and development, with the transcriptional response to cytokinin being mediated by the type-B response regulators. In Arabidopsis (Arabidopsis thaliana), type-B response regulators (ARABIDOPSIS RESPONSE REGULATORS [ARRs]) form three subfamilies based on phylogenic analysis, with subfamily 1 having seven members and subfamilies 2 and 3 each having tw...

The regulation of cytokinin oxidase activity in callus tissues of Phaseolus vulgaris L. cv Great Northern has been examined using an assay based on the oxidation of N(6)-(Delta(2)-isopentenyl)adenine-8-(14)C (i(6) Ade-8-(14)C) to adenine. Solutions of exogenous cytokinins applied directly to the surface of the callus tissues induced relatively rapid increases in cytokinin oxidase activity. The ...

Plant root development is mediated by the concerted action of the auxin and cytokinin phytohormones, with cytokinin serving as an antagonist of auxin transport. Here, we identify the AUXIN UP-REGULATED F-BOX PROTEIN1 (AUF1) and its potential paralog AUF2 as important positive modifiers of root elongation that tether auxin movements to cytokinin signaling in Arabidopsis (Arabidopsis thaliana). T...

Azotobacter vinelandii OP was grown to stationary phase in defined medium. The cell-free culture medium was analyzed for cytokinin content by XAD-2 and Sephadex LH-20 chromatography, thin-layer chromatography, tobacco callus bioassay, and enzyme immunoassay. Three cytokinin-active fractions were detected and tentatively identified as trans-zeatin, isopentenyladenosine, and isopentenyladenine. T...

Using in silico methods, several putative phytohormone-responsive cis-elements in the Oryza sativa non-symbiotic haemoglobin (NSHB) 1-4 and Arabidopsis thaliana NSHB1-2 promoters have been identified. An OsNSHB2 promoter::GUS reporter gene fusion shows tissue-specific expression in A. thaliana. GUS expression was observed in roots, the vasculature of young leaves, in flowers, and in the pedicel...

The phytopathogenic actinomycete Rhodococcus fascians D188 relies mainly on the linear plasmid-encoded fas operon for its virulence. The bacteria secrete six cytokinin bases that synergistically redirect the developmental program of the plant to stimulate proliferation of young shoot tissue, thus establishing a leafy gall as a niche. A yeast-based cytokinin bioassay combined with cytokinin prof...

We have isolated 20 cDNA clones for which the corresponding mRNAs accumulate 2- to 20-fold within 4 hr of cytokinin addition to cytokinin-starved soybean suspension cultures. These changes in mRNA levels precede the greening and cell growth induced by cytokinin in this system. Treatment with cycloheximide before cytokinin addition enhances the accumulation of these messages. In addition, the ab...

As a result of biological screening among synthetic compounds that have growth regulatory activities in culture tissues in vitro and in vivo in plants, 5 perspective substances were chosen as the substitutes of phytohormones. Thus, it was found that Ivin (N-oxide 2,6-diniethylpyridine) revealed predominant cytokinin activity in vitro and a cytokinin-gibberelin activity in vivo; Methyur (Na-deri...