Cytokinin biosynthesis in a cell‐free system from cytokinin‐autotrophic tobacco tissue cultures

Chen, Chong-Maw; Melitz, Debra K.

doi:10.1016/0014-5793(79)80452-4

Cited by 100 publications

(29 citation statements)

References 21 publications

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“…In tumorous plant tissue this enzyme may represent the rate-limiting step in cytokinin biosynthesis (Akiyoshi et al, 1983). Furthermore, this enzyme may have a role in nontumorous tissues since a partially purified enzyme with ipt activity has been reported in tobacco cells (Chen and Melitz, 1979).…”

Section: Resultsmentioning

confidence: 99%

Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene.

et al. 1989

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Cytokinins, a class of phytohormones, appear to play an important role in the processes of plant development. We genetically engineered the Agrobacterium tumefaciens isopentenyl transferase gene, placing it under control of a heat-inducible promoter (maize hsp70). The chimeric hsp7O isopentenyl transferase gene was transferred to tobacco and Arabidopsis plants. Heat induction of transgenic plants caused the isopentenyl transferase mRNA to accumulate and increased the level of zeatin 52-fold, zeatin riboside 23-fold, and zeatin riboside 5'-monophosphate twofold. At the control temperature zeatin riboside and zeatin riboside 5'-monophosphate in transgenic plants accumulated to levels 3 and 7 times, respectively, over levels in wild-type plants. This uninduced cytokinin increase affected various aspects of development. In tobacco, these effects included release of axillary buds, reduced stem and leaf area, and an underdeveloped root system. In Arabidopsis, reduction of root growth was also found. However, neither tobacco nor Arabidopsis transgenic plants showed any differences relative to wild-type plants in time of flowering. Unexpectedly, heat induction of cytokinins in transgenic plants produced no changes beyond those seen in the uninduced state. The lack of effect from heat-induced increases could be a result of the transient increases in cytokinin levels, direct or indirect induction of negating factor(s), or lack of a corresponding level of competent cellular factors. Overall, the effects of the increased levels of endogenous cytokinins in non-heat-shocked transgenic plants seemed to be confined to aspects of growth rather than differentiation. Since no alterations in the programmed differentiation pattern were found with increased cytokinin levels, this process may be controlled by components other than absolute cytokinin levels.

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Section: Resultsmentioning

confidence: 99%

Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene.

et al. 1989

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“…The slime mold enzyme is the only enzyme that has been purified extensively, 6700-fold (Ihara et al, 1984). The tobacco enzyme was highly unstable and attempts to achieve over 40-fold purification led to a complete loss of activity (Chen and Melitz, 1979). There are indications for a similar biosynthetic pathway in monocots.…”

Section: Cytokinin Biosynthesismentioning

confidence: 99%

Cytokinins: Biosynthesis metabolism and perception

Mok

Martin

Mok

2000

In Vitro Cell.Dev.Biol.-Plant

108

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SummaryCytokinins are essential hormones for plant growth and development. They are also of vital importance for in vitro manipulations of plant cells and tissues. The biological activities and chemistry of cytokinins are well defined but very little is known about their mode of action and it is only recently that cytokinin genes have been identified in plants. 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.

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“…Cytokinin has been suggested to be synthesized in specific sites such as the root tip (19), immature kernel (20), and shoot apical meristem (21). However, the activity of plant IPT has been reported in only a few tissues such as immature maize kernels (20) and cytokinin autonomous tobacco callus (22,23). As the enzyme seemed to be highly unstable and low in content, biochemical approaches to purify and characterize plant IPT have been hampered.…”

mentioning

confidence: 99%

Identification of Genes Encoding Adenylate Isopentenyltransferase, a Cytokinin Biosynthesis Enzyme, inArabidopsis thaliana

Takei¹,

Sakakibara

Sugiyama³

2001

Journal of Biological Chemistry

450

319

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The initial step in the de novo biosynthesis of cytokinin in higher plants is the formation of isopentenyladenosine 5-monophosphate (iPMP) from AMP and dimethylallylpyrophosphate (DMAPP), which is catalyzed by adenylate isopentenyltransferase (IPT). Although cytokinin is an essential hormone for growth and development, the nature of the enzyme for its biosynthesis in higher plants has not been identified. Herein, we describe the molecular cloning and biochemical identification of IPTs from Arabidopsis thaliana. Eight cDNAs encoding putative IPT, designated as AtIPT1 to AtIPT8, were picked up from A. thaliana. The Escherichia coli transformants expressing the recombinant proteins excreted cytokinin species into the culture medium except for that expressing AtIPT2 that is a putative tRNA IPT. A purified recombinant AtIPT1 catalyzed the formation of iPMP from DMAPP and AMP. These results indicate that the small multigene family contains both types of isopentenyltransferase, which could synthesize cytokinin and mature tRNA.

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Cytokinin biosynthesis in a cell‐free system from cytokinin‐autotrophic tobacco tissue cultures

Cited by 100 publications

References 21 publications

Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene.

Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene.

Cytokinins: Biosynthesis metabolism and perception

Identification of Genes Encoding Adenylate Isopentenyltransferase, a Cytokinin Biosynthesis Enzyme, inArabidopsis thaliana

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