title: High molecular size humic substances enhance phenylpropanoid metabolism in maize (Zea mays L.).
abstract: A high molecular weight humic fraction (>3,500 Da) was characterized chemically by DRIFT and 1H NMR spectroscopy, and was applied to Zea mays L. plants to evaluate its effect on phenylpropanoid metabolism. The activity and gene expression of phenylalanine (tyrosine) ammonia-lyase (PAL/TAL), and the concentrations of phenolics and their amino acid precursors phenylalanine and tyrosine were assayed. Maximum induction of PAL/TAL activity and expression was obtained when the concentration of added humic substance was 1 mg C/l hydroponic solution. Phenylalanine and tyrosine significantly decreased (-16% and -22%, respectively), and phenolic compounds increased in treated plants. The effects of the humic substance could be ascribed partly to indoleacetic acid (27 nmol/mg C) in the humic fraction. Our results suggest that this humic fraction induces changes in phenylpropanoid metabolism. This is the first study that shows a relationship between humic substances and the phenylpropanoid pathway.
authors.affiliation: Department of Agricultural Biotechnologies, University of Padova, Agripolis, Viale dell'Università 16, 35020 Legnaro, Padova, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Schiavon
authors.forename: Diego
authors.initials: D
authors.lastname: Pizzeghello
authors.forename: Adele
authors.initials: A
authors.lastname: Muscolo
authors.forename: Silvia
authors.initials: S
authors.lastname: Vaccaro
authors.forename: Ornella
authors.initials: O
authors.lastname: Francioso
authors.forename: Serenella
authors.initials: S
authors.lastname: Nardi
mesh_terms: D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006812:Humic Substances; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D014443:Tyrosine / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology / Q000378:metabolism*
chemical_list: D006812:Humic Substances; D010636:Phenols; D010940:Plant Proteins; D014443:Tyrosine; D010649:Phenylalanine; D010650:Phenylalanine Ammonia-Lyase