Investigation of cell wall properties of xylan deficient IRX mutants and relation to enzymatic digestibility in Arabidopsis thaliana

Genetic manipulation of plant feedstock characteristics for improved digestibility is a key research avenue in the commercialization of lignocellulosic feedstocks for biofuel production. In this study, we investigate phenotypic changes of the cell wall in a set of IRX mutants (IRX9, IRX10, and IRX15-15L) deficient in glucuronoxylan synthesis and deposition proteins using the model plant Arabidopsis thaliana, and relate these changes to enzyme accessibility and hydrolysis yields. Cell wall - water interactions are examined using differential scanning calorimetry-thermoporemetry (DSC-TP), spin-spin T2 NMR relaxometry, and water retention value, with subsequent observations being correlated to cell wall compositional and structural properties. Crystallinity observations using wide angle x-ray scattering (WAXS) provides evidence of differing cellulose deposition patterns. Imaging analysis of cell wall structural features using atomic force microscopy (AFM) and confocal microscopy coupled with GFP labelled CBMs provide visual evidence of significant differences in cellulose fibril structure and xylan deposition patterns. These findings are linked back to enzyme binding and digestibility assays and may yield an improved understanding of the impact of xylan deposition during cell wall growth on cellulose accessibility.