Investigating the roles of phenylpropanoids in the growth and development of Zea mays L.

Abstract

The Poaceae includes some of the most important food, fiber, and bio-fuel crops. While there have been many studies investigating the function of phenylpropanoids in this family, most of our understanding is based on correlative data rather than experimental evidence. The current study was conducted to evaluate the roles of phenylpropanoids in the growth and development of Zea mays and to develop an experimental model for further investigations. Z. mays seedlings were grown in vitro with various concentrations of the competitive phenylalanine ammonia lyase inhibitor, 2-aminoindane-2-phosphonic acid (AIP). Ferulic acid, a downstream biosynthetic product, was added to determine if it could rescue the induced phenotypes. At lower concentrations of AIP, plants exhibited elongated roots and shoots, but at higher concentrations, growth was extremely stunted. At the cellular level, the epidermal cells of roots cultured with AIP exhibited a loss of intercellular adhesion and organization, and their cell walls were more readily degraded by enzymatic digestion. These characteristics were accompanied by significant reductions in primary cell wall autofluorescence, indicating that less ferulic acid and other phenolics were incorporated in the cell wall. The majority of these symptoms could be partially or entirely rescued by ferulic acid, providing further evidence that these differences were due to the inhibition of phenylpropanoid biosynthesis. This study provides experimental evidence supporting and expanding upon hypothesized functions of phenylpropanoids in the growth and development of Z. mays and provides an experimental system for further investigations in the Poaceae and other taxonomic groups.