Structure, Chemical Composition, and Xylanase Degradation of External Layers Isolated from Developing Wheat Grain

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• 作者：Johnny Beaugrand ; David Crô ; nier ; Pascal Thiebeau ; Lucas Schreiber ; Philippe Debeire ; and Brigitte Chabbert
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2004
• 出版时间：November 17, 2004
• 年：2004
• 卷：52
• 期：23
• 页码：7108 - 7117
• 全文大小：473K
• 年卷期：v.52,no.23(November 17, 2004)
• ISSN：1520-5118

文摘

The external layers of wheat grain were investigated during maturation with respect to chemical andstructural features and xylanase degradability. Cytochemical changes were observed in the isolatedperipheral tissues of the wheat grain at four defined stages following anthesis. Marked chemicalchanges were highlighted at 11 days after anthesis, for which protein and lipid contents varied weakly.The profile of esterified ferulic acid showed large variation in the maturing peripheral layers of grainin contrast to the deposition of ferulate dimers, p-coumaric and sinapic acids. Lignin was monitoredat the latest stages of ripening, which corresponds to the cessation of reserve accumulation in thegrain. Arabinoxylans (AX) reached a maximum at 20 days and did not display any significant changein arabinosyl substitution proportion until ripeness. When submitted to xylanase, all outer layers weresimilarly altered in the proportion of soluble AX except for the peripheral tissues of the 11-day-agedwheat grain that had very little AX. Aleurone and nucellar layers were mostly degraded, whereaspericarp stayed intact at all stages of maturation. This degradation pattern was connected with thepreferential immunolocalization of xylanase in aleurone and nucellar layers irrespective of thedevelopmental stages. Further chemical examination of the enzyme-digested peripheral tissues ofthe grain supports the facts that ferulic ester is not a limiting factor in enzyme efficiency. Arabinosebranching, ferulic dimers, and ether-linked monomers that are deposited early in the external layerswould have more relevance to the in situ degradability of AX.Keywords: Peripheral tissues of the wheat grain (Triticum aestivum); maturation; cell wall; arabinoxylans; xylanase; immunolocalization; phenolic acids; lignin; aleurone; cutin, alkylresorcinol