Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/25/2007
Publication Date: 7/1/2007
Citation: Leclere, S.L., Schmelz, E.A., Chourey, P.S. 2007. Phenolic compounds accumulate specifically in maternally-derived tissues of developing maize kernels. Cereal Chemistry. 84(4):350-356. Interpretive Summary: Flavonoids and phenolics are chemicals that are synthesized in plants and are known to provide protection against pest and pathogens. Our previous studies at cellular level suggested a possibility of these compounds at the base of developing seeds in maize. A collaborative study between scientists from Crop Genetics & Environmental Research and Chemistry Units at the CMAVE, Gainesville, was initiated to characterize the nature of these chemicals. The present report, based on the use of various sophisticated analytical methods (e.g., high performance liquid chromatography, gas chromatography and mass spectrometry), shows that these chemicals constitute a complex mixture of phenolic compounds which may function as antimicrobial agents at the major transport route of sugar and nutrients to a developing seed. Such basic knowledge is critical towards breeding of crop plants with natural resistance against pest and pathogens.
Technical Abstract: Phenolic compounds and flavonoids function in the natural resistance of plants to insects, pathogens, and abiotic stresses. We have investigated the flavonoid and phenolic acid content in developing maize kernels from 8 to 28 days after pollination, and found a complex mixture of phenolic compounds present in both upper (starchy, storage region) and lower (basal endosperm and pedicel) parts of kernels. The accumulation of several analytes appears to be independent of the regulatory transcription factor encoded by pericarp color 1 (P1) locus, and there are large differences in the abundance of these compounds both developmentally and between the genetic backgrounds represented by inbred lines 4Co63, W22, and W23. We dissected and analyzed various tissue types and demonstrated that the majority of these compounds are present in pedicels, with lesser amounts in pericarp, aluerone, PC-region, and cob glumes, whereas very few phenolics were detected in endosperm. We have determined the molecular masses of major analytes to be 410, 440, and 862 mass units, and all have UV characteristics similar to hydroxycinnamic acids. Taken together these data indicate that complex phenolic acid compounds rather than flavonoids are the major phenolic constituents present in developing kernels, and the accumulation of these compounds is developmentally regulated suggesting they may play important roles in seed development.