title: Gene expression patterns, localization, and substrates of polyphenol oxidase in red clover ( Trifolium pratense L.).
abstract: Polyphenol oxidase (PPO) genes and their corresponding enzyme activities occur in many plants; natural PPO substrates and enzyme/substrate localization are less well characterized. Leaf and root PPO activities in Arabidopsis and five legumes were compared with those of high-PPO red clover ( Trifolium pratense L.). Red clover PPO enzyme activity decreased leaves > stem > nodules > peduncle = petiole > embryo; PPO1 and PPO4 genes were expressed early in leaf emergence, whereas PPO4 and PPO5 predominated in mature leaves. PPO1 was expressed in embryos and nodules. PPO substrates, phaselic acid and clovamide, were detected in leaves, and clovamide was detected in nodules. Phaselic acid and clovamide, along with caffeic and chlorogenic acids, were suitable substrates for PPO1, PPO4, and PPO5 genes expressed in alfalfa ( Medicago sativa L.) leaves. PPO enzyme presence and activity were colocalized in leaves and nodules by cytochemistry. Substrates and PPO activity were localized in developing squashed cell layer of nodules, suggesting PPO may have a developmental role in nodules.
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University , Gogerddan, Aberystwyth, Ceredigion SY23 3EE, Wales, U.K.
authors.forename: K Judith
authors.initials: KJ
authors.lastname: Webb
authors.forename: Alan
authors.initials: A
authors.lastname: Cookson
authors.forename: Gordon
authors.initials: G
authors.lastname: Allison
authors.forename: Michael L
authors.initials: ML
authors.lastname: Sullivan
authors.forename: Ana L
authors.initials: AL
authors.lastname: Winters
mesh_terms: D002109:Caffeic Acids / Q000378:metabolism; D004156:Catechol Oxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002726:Chlorogenic Acid / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008293:Malates / Q000378:metabolism; D005810:Multigene Family; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D029921:Trifolium / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D002109:Caffeic Acids; D008293:Malates; D010940:Plant Proteins; C521943:phaselic acid; D002726:Chlorogenic Acid; D004156:Catechol Oxidase