title: Potato tuber cytokinin oxidase/dehydrogenase genes: biochemical properties, activity, and expression during tuber dormancy progression.
abstract: The enzymatic and biochemical properties of the proteins encoded by five potato cytokinin oxidase/dehydrogenase (CKX)-like genes functionally expressed in yeast and the effects of tuber dormancy progression on StCKX expression and cytokinin metabolism were examined in lateral buds isolated from field-grown tubers. All five putative StCKX genes encoded proteins with in vitro CKX activity. All five enzymes were maximally active at neutral to slightly alkaline pH with 2,6-dichloro-indophenol as the electron acceptor. In silico analyses indicated that four proteins were likely secreted. Substrate dependence of two of the most active enzymes varied; one exhibiting greater activity with isopentenyl-type cytokinins while the other was maximally active with cis-zeatin as a substrate. [(3)H]-isopentenyl-adenosine was readily metabolized by excised tuber buds to adenine/adenosine demonstrating that CKX was active in planta. There was no change in apparent in planta CKX activity during either natural or chemically forced dormancy progression. Similarly although expression of individual StCKX genes varied modestly during tuber dormancy, there was no clear correlation between StCKX gene expression and tuber dormancy status. Thus although CKX gene expression and enzyme activity are present in potato tuber buds throughout dormancy, they do not appear to play a significant role in the regulation of cytokinin content during tuber dormancy progression.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Northern Crop Science Laboratory, 1605 Albrecht Boulevard N, Fargo, ND 58102-2765, USA. Electronic address: jeff.suttle@ars.usda.gov.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Suttle
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Northern Crop Science Laboratory, 1605 Albrecht Boulevard N, Fargo, ND 58102-2765, USA.
authors.forename: Linda L
authors.initials: LL
authors.lastname: Huckle
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Northern Crop Science Laboratory, 1605 Albrecht Boulevard N, Fargo, ND 58102-2765, USA.
authors.forename: Shunwen
authors.initials: S
authors.lastname: Lu
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Northern Crop Science Laboratory, 1605 Albrecht Boulevard N, Fargo, ND 58102-2765, USA.
authors.forename: Donna C
authors.initials: DC
authors.lastname: Knauber
mesh_terms: D001483:Base Sequence; D003583:Cytokinins / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D018519:Meristem / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D057445:Plant Dormancy; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D035281:Plant Tubers / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D018749:RNA, Plant / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D013379:Substrate Specificity
chemical_list: D003583:Cytokinins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D018749:RNA, Plant; D010088:Oxidoreductases; C019984:cytokinin oxidase
keywords: Cytokinin; Dormancy; Potato; Solanum tuberosum; Tuber