IMPACT OF LIGNIN STRUCTURE AND CELL WALL RETICULATION ON MAIZE CELL WALL DEGRADABILITY

摘要

Grass cell walls are complex molecular assemblies involving polysaccharidic (cellulose and hemicelluloses) and phenolic (lignins and phydroxycinnamic acids) components. Lignin content is recognized as the first limiting factor negatively correlated with cell wall degradability. However, it is not possible to construct plants with drastically reduced lignin contents since a minimum of lignification is needed to ensure plant posture, avoid lodging and protect the plant against parasitic attack. For this reason, we selected 8 maize recombinant inbred lines to assess both the impact of lignin structure and organization, and the impact of cell wall reticulation by p-hydroxycinnamic acids on cell wall degradability independently of the main "lignin content" factor. These recombinant lines and there parents were analyzed for cell wall residue content, esterified and etherified p-hydroxycinnamic acids content, lignin content and structure and in vitro degradability. Amongst these biochemical parameters, lignin structure and esterified pcoumaric acid content showed high significant correlation with in vitro cell wall degradability (r = -0.82 and r = -0.72 respectively). A multiple regression analysis was also carried out. More than 80% of the observed cell wall degradability variations within these ten lines could be explained by a regression model which includes two main explanatory factors: lignin content in the cell wall and a composite variate which estimated the proportion of S lignin units esterified by p-coumaric acid. In this study, we thus highlighted biochemical factors involved in cell wall degradability limitation and defined potential parameters to select in order to improve cell wall degradability and lignocelluloses valorization.