High Molecular Size Humic Substances Enhance Phenylpropanoid Metabolism in Maize (Zea mays L.)

• DOI: 10.1007/s10886-010-9790-6
• Publication Date: 2010-05-17T16:57:44Z
• Authors: Michela Schiavon; Diego Pizzeghello; Adele Muscolo; Silvia Vaccaro; Ornella Francioso; Serenella Nardi
• Keywords: 2. Zero hunger; Magnetic Resonance Spectroscopy; Phenylalanine; DRIFT-HNMR; high molecular weight humic fraction; phenylalanine (tyrosine) ammonia-lyase (PAL/TAL); HIGH MOLECULAR SIZE HUMIC SUBSTANCES; DRIFT; 1H NMR; PHENYLALANINE (TYROSINE) AMMONIA-LYASE; PHENOLS; 04 agricultural and veterinary sciences; Zea mays; Phenols; Gene Expression Regulation, Plant; Spectroscopy, Fourier Transform Infrared; Tyrosine; 0401 agriculture, forestry, and fisheries; Humic Substances; Phenylalanine Ammonia-Lyase; Plant Proteins

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.