In:
Plant Physiology, Oxford University Press (OUP), Vol. 112, No. 3 ( 1996-11-01), p. 1035-1043
Abstract:
Metabolic control of cytokinin oxidase by its substrate was investigated in planta using wild-type (WT) and conditionally ipt gene-expressing transgenic (IPT) tobacco (Nicotiana tabacum L.) callus cultures and plants. The derepression of the tetracycline (Tc)-dependent ipt gene transcription was followed by a progressive, more than 100-fold increase in total cytokinin content in IPT calli. The activity of cytokinin oxidase extracted from these calli began to increase 16 to 20 h after gene derepression, and after 13 d it was 10-fold higher than from Tc-treated WT calli. An increase in cytokinin oxidase activity, as a consequence of elevated cytokinin levels, was found in detached leaves (8-fold after 4 d) and in roots of intact plants (4-fold after 3 d). The partially purified cytokinin oxidase from WT, repressed IPT, and Tc-derepressed IPT tobacco calli exhibited similar characteristics. It had the same broad pH optimum (pH 6.5–8.5), its activity in vitro was enhanced 4-fold in the presence of copper-imidazole, and the apparent Km(N6-[[delta] 2iso-pentenyl]adenine) values were in the range of 3.1 to 4.9 [mu] M. The increase in cytokinin oxidase activity in cytokinin-overproducing tissue was associated with the accumulation of a glycosylated form of the enzyme. The present data indicate the substrate induction of cytokinin oxidase activity in different tobacco tissues, which may contribute to hormone homeostasis.
Type of Medium:
Online Resource
ISSN:
1532-2548
,
0032-0889
DOI:
10.1104/pp.112.3.1035
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
1996
detail.hit.zdb_id:
2004346-6
detail.hit.zdb_id:
208914-2
SSG:
12
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