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Phenolic Compounds Accumulate Specifically in Maternally-Derived Tissues of Developing Maize Kernels

¹USDA, Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Chemistry Unit, 1600 SW 23rd Drive, Gainesville, FL. ²University of Florida, Department of Plant Pathology and Department of Agronomy, Gainesville, FL. ³Corresponding author. Phone: 352-392-3631 ext 345. Fax: 352-392-6532. E-mail: pchourey@ifas.ufl.edu

Phenolic compounds function in natural resistance of plants to insects, pathogens, and abiotic stresses. We investigated the flavonoid and phenolic acid content in developing maize kernels from 8 to 28 days after pollination and found a complex and developmentally dynamic mixture of compounds. LC-MS analysis showed no detectable levels of the flavonoid maysin in any of the kernel tissue tested. Accumulation of the three most abundant analytes was developmentally and spatially regulated and independent of the regulatory transcription factor pericarp color 1 (P1). Major analytes have UV characteristics similar to hydroxycinnamic acids. LC-MS indicates molecular weights of 410, 440, and 862 mass units, representing coumaroylferuloylputrescine (CFP), diferuloylputrescine (DFP), and a novel compound, respectively. There are large differences in the abundance of these compounds between genetic backgrounds, and accumulation increases with age. We dissected and analyzed various tissue types and demonstrated that the majority of these compounds are present in pedicels, with lesser amounts in pericarp and placento-chalazal regions. These data indicate that complex phenolic acids and amides rather than flavonoids are the major phenolic constituents in developing kernels, and accumulation of these compounds is developmentally and spatially regulated, with the greatest abundance in maternal tissues surrounding the kernel.