Kinetin

About: Kinetin is a research topic. Over the lifetime, 7856 publications have been published within this topic receiving 135550 citations. The topic is also known as: Kinetin.

Cytokinin controls the cell cycle at mitosis by stimulating the tyrosine dephosphorylation and activation of p34cdc2-like H1 histone kinase

Abstract: In excised pith parenchyma from Nicotiana tabacum L. cv. Wisconsin Havana 38, auxin (naphthalene-1-acetic acid) together with cytokinin (6-benzylaminopurine) induced a greater than 40-fold increase in a p34cdc2-like protein, recoverable in the p13suc1-binding fraction, that had high H1 histone kinase activity, but enzyme induced without cytokinin was inactive. In suspension-cultured N. plumbaginifolia Viv., cytokinin (kinetin) was stringently required only in late G2 phase of the cell division cycle (cdc) and cells lacking kinetin arrested in G2 phase with inactive p34cdc2-like H1 histone kinase. Control of the Cdc2 kinase by inhibitory tyrosine phosphorylation was indicated by high phosphotyrosine in the inactive enzyme of arrested pith and suspension cells. Yeast cdc25 phosphatase, which is specific for removal of phosphate from tyrosine at the active site of p34cdc2 enzyme, was expressed in bacteria and caused extensive in-vitro activation of p13suc1-purified enzyme from pith and suspension cells cultured without cytokinin. Cytokinin stimulated the removal of phosphate, activation of the enzyme and rapid synchronous entry into mitosis. Therefore, plants can control cell division by tyrosine phosphorylation of Cdc2 but differ from somatic animal cells in coupling this mitotic control to hormonal signals.

In vitro micropropagation of Gymnema sylvestre - a multipurpose medicinal plant.

Abstract: The nature of the explant, seedling age, medium type, plant growth regulators, complex extracts (casein hydrolysate, coconut milk, malt extract and yeast extract) and antioxidants (activated charcoal, ascorbic acid, citric acid and polyvinylpyrrolidone) markedly influenced in vitro propagation of Gymnema sylvestre. A maximum number of shoots (57.2) were induced from 30 day old seedling axillary node explants on Murashige and Skoog (MS) medium containing 6-benzyladenine (1 mg l−1), kinetin (0.5 mg l−1), 1-napthalene acetic acid (0.1 mg l−1), malt extract (100 mg l−1) and citric acid (100 mg l−1). High frequency of rooting was obtained in axillary node explant derived shoots (50%) on half strength MS medium supplemented with IBA (3 mg l−1). The plantlets, thus developed, were hardened and successfully established in natural soil.

Inhibition of ethylene production by cobaltous ion.

Abstract: The effect of Co(2+) on ethylene production by mung bean (Phaseolus aureus Roxb.) and by apple tissues was studied. Co(2+), depending on concentrations applied, effectively inhibited ethylene production by both tissues. It also strongly inhibited the ethylene production induced by IAA, kinetin, IAA plus kinetin, Ca(2+), kinetin plus Ca(2+), or Cu(2+) treatments in mung bean hypocotyl segments. While Co(2+) greatly inhibited ethylene production, it had little effect on the respiration of apple tissue, indicating that Co(2+) does not exert its inhibitory effect as a general metabolic inhibitor. Ni(2+), which belongs to the same group as Co(2+) in the periodic table, also markedly curtailed both the basal and the induced ethylene production by apple and mung bean hypocotyl tissues.In a system in which kinetin and Ca(2+) were applied together, kinetin greatly enhanced Ca(2+) uptake, thus enhancing ethylene production. Co(2+), however, slightly inhibited the uptake of Ca(2+) but appreciably inhibited ethylene production, either in the presence or in the absence of kinetin. Tracer experiments using apple tissue indicated that Co(2+) strongly inhibited the in vivo conversion of l-[U-(14)C]methionine to (14)C-ethylene. These data suggest that Co(2+) inhibited ethylene production by inhibiting the conversion of methionine to ethylene, a common step which is required for ethylene formation by higher plants.Co(2+) is known to promote elongation, leaf expansion, and hook opening in excised plant parts in response to applied auxins or cytokinins. Since ethylene is known to inhibit these growth phenomena, it is suggested that Co(2+) exerts its promotive effect, at least in part, by inhibiting ethylene formation.

Interaction of Kinetin and Various Inhibitors in the Growth of Soybean Tissue

Abstract: The growth of kinetin-requiring soybean callus was inhibited by the purine analogs 2,6-diaminopnrine, 8-azaguanine and 8-azaadenine. The purine analog 6-mercaptopnrine and the antibiotic puromycin were not effective as inhibitors at the concentrations employed. Reversal of the inhibition was attempted by raising the kinetin concentration. Kinetin did not reverse the inhibition due to 2,6-dianiinopurine but it did lessen to some extent the inhibition due to 8-azagnanine. It is suggested the kinetin affects RNA metabolism.