Cytokinin hormones are crucial regulators of a large number of processes in plant development. Recently, significant progress has been made toward the elucidation of the molecular details of cytokinin that has led to a model for signal transduction involving a phosphorylation cascade. However, the current knowledge of cytokinin action remains largely unknown and does not explain the different r...

The cytokinin receptor AHK3 of Arabidopsis thaliana plays a predominant role in shoot development. A study of the hormone-binding characteristics of AHK3 compared with the mainly root-confined receptor CRE1/AHK4 has been accomplished using a live-cell binding assay on transgenic bacteria expressing individual receptor proteins. Both receptors bound trans-zeatin (tZ) with high affinity. Scatchar...

In cultured Bright Yellow-2 (BY-2) tobacco (Nicotiana tabacum) cells, the depletion of auxin (2,4-dichlorophenoxyacetic acid) in the culture medium induces the accumulation of starch. This is accelerated by the addition of cytokinin (benzyladenine). Light and electron microscopic observations revealed that this amyloplast formation involves drastic changes in plastid morphology. The effects of ...

Hydroxylated cytokinin, 2-methylthio-N6-(4-hydroxy-3-methylbut-2-enyl) adenosine, was found in the tRNA of Azotobacter vinelandii. This cytokinin had the trans configuration, unlike the cis configuration reported for that from other bacteria. Culture-condition-dependent changes in the content of this thiocytokinin and a few other thionucleosides in the tRNA of this bacterium have been observed.

Cytokinin has been reported to mimic some of the effects of light on de-etiolation responses in dark-grown Arabidopsis seedlings. The interaction between cytokinin and light was examined by analyzing cytokinin dose and light fluence effects on hypocotyl elongation in wild-type and mutant Arabidopsis seedlings with defects in light or hormone responses. It was found that (a) cytokinin and light-...

Cytokinin deficiency causes pleiotropic developmental changes such as reduced shoot and increased root growth. It was investigated whether cytokinin-deficient tobacco plants, which overproduce different cytokinin oxidase/dehydrogenase enzymes, show changes in different sink and source parameters, which could be causally related to the establishment of the cytokinin deficiency syndrome. Ultrastr...

Cytokinin activity in the culture medium of four pathogenic strains of Corynebacterium fascians varied from 168 to 0.4 mug of kinetin (6-furfurylaminopurine) equivalents per liter, as compared to 0.2 in an avirulent control. N(6)-Isopentenyladenine was the predominant cytokinin in the medium of all five strains, and its increased production was correlated with the degree of pathogenicity; howev...

For the last 50 years, scientists have recognized that varying ratios of the plant hormones cytokinin and auxin induce plant cells to form particular tissues: undifferentiated calli, shoot structures, root structures, or a whole plant. Proliferation of undifferentiated callus tissue, greening, and the formation of shoot structures are all cytokinin-dependent processes. Habituation refers to a n...

The phytohormone cytokinin is an important regulator of plant growth and development; however, relatively few genes that mediate cytokinin responses have been identified. Genome-wide analyses of Arabidopsis seedlings using the approximately 8,300-element Affymetrix Arabidopsis GeneChips (Affymetrix, Santa Clara, CA) to examine cytokinin-responsive genes were conducted, revealing at least 30 gen...

Three cytokinin-over-producing mutants of the moss, Physcomitrella patens, have been shown to convert [8-(14)C]adenine to N(6)-[(14)C](Delta(2)-isopentenyl)adenine, the presence of which was confirmed by thin layer chromatography, high performance liquid chromatography, and recrystallization to constant specific radioactivity. The labeled cytokinin was detected in the culture medium within 6 ho...