Zeatin biosynthesis from N6-(Δ2-isopentenyl)adenine in Actinidia and other woody plants
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A survey of 30 species of woody plants in 20 families of dicotyledonous angiosperms indicated that the ability to accumulate io6Ade in 24-hr feeds with 30 μM i 6Ade was restricted to certain systematic groups—e.g., order Ericales, families Oleaceae and Rubiaceae.Abstract:
Tissue cultures of Actinidia kolomikta can be maintained as callus through repeated passages on a nutrient medium devoid of cytokinin but containing inorganic nutrients, sucrose, and other basal organics plus auxin. Under these conditions, actively growing callus contained 2 and 0.5 nmol of the cytokinins zeatin [io6Ade; 6-(4-hydroxy-3-methylbut-2-enylamino)purine] and N6-(Δ2-isopentenyl)adenine (i6Ade), respectively, per gram (fresh weight). When tissues were transferred from cytokininless medium to 30 μM i6Ade, endogenous io6Ade increased linearly to 160 nmol/g (fresh weight) during 8 hr, and i6Ade increased to 5 nmol/g (fresh weight) in 2 hr and then declined. The apparent Km for i6Ade in A. kolomikta and Actinidia chinensis × Actinidia arguta callus and in tissue slices of A. arguta stems was 12 μM. In addition, the reaction(s) converting i6Ade to io6Ade was O2-requiring and specific for i6Ade versus N6-(Δ2-isopentenyl)adenosine (i6A). When A. kolomikta callus was fed 30 μM i6A, io6Ade increased and reached a concentration corresponding to 6 nmol/g (fresh weight) in 8 hr. Ribosylzeatin (io6A) did not increase. Under N2 during i6A feeds, i6A accumulated rather than being metabolized to i6Ade, suggesting that i6A normally may be metabolized via i6AMP and i6Ade to io6Ade. A survey of 30 species of woody plants in 20 families of dicotyledonous angiosperms indicated that the ability to accumulate io6Ade (≥10 nmol/g) in 24-hr feeds with 30 μM i6Ade was restricted to certain systematic groups—e.g., order Ericales, families Oleaceae and Rubiaceae. This suggests that plants may differ in their pathways for io6Ade biosynthesis and that cytokinin biochemistry has potential as a taxonomic character above the species and genus levels.read more
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Journal ArticleDOI
Cytokinin metabolism and action
David W. S. Mok,Machteld C. Mok +1 more
TL;DR: This review centers on cytokinin metabolism with connecting discussions on biosynthesis and signal transduction, and important findings are summarized with emphasis on metabolic enzymes and genes.
Journal ArticleDOI
Regulation of in vitro somatic embryogenesis with emphasis on to the role of endogenous hormones
TL;DR: The article is centered on the effect that the endogenous hormone concentrations in the initial explants and in the tissue cultures derived from them could play in the induction and expression of somatic embryogenesis.
Book ChapterDOI
Plant Growth Regulators II: Cytokinins, their Analogues and Antagonists
TL;DR: Hormones in plants differ from most of those in animals by having pleiotropic effects; that is, they are involved in the control of a wide range of developmental processes, but the effect of a hormone on any developmental process depends on the species.
Journal ArticleDOI
Cytokinins: biosynthesis, metabolism and perception.
TL;DR: This review summarizes the current status of knowledge on cytokinin biosynthesis, metabolism and signal transduction, with an emphasis on genes encoding metabolic enzymes and putative receptors, and genes rapidly induced by cytokinins.
Journal ArticleDOI
Chromosome studies in some Actinidia taxa and implications for breeding
TL;DR: Microsporogenesis was studied in eleven Actinidia taxa including A. deliciosa (kiwifruit) and in an interspecific hybrid, indicating there may be genetic control of chiasmata distribution in these polyploids.
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