A pectin methyltransferase modulates polysaccharide dynamics and interactions in Arabidopsis primary cell walls: Evidence from solid-state NMR.

Plant cell walls contain cellulose embedded in matrix polysaccharides. Understanding carbohydrate structures and interactions is critical to the production of biofuel and biomaterials using these natural resources. Here we present a solid-state NMR study of cellulose and pectin in 13C-labeled cell walls of Arabidopsis wild-type and mutant plants. Using 1D 13C and 2D 13C–13C correlation experiments, we detected a highly branched arabinan structure in qua2 and tsd2 samples, two allelic mutants for a pectin methyltransferase. Both mutants show close physical association between cellulose and the backbones of pectic homogalacturonan and rhamnogalacturonan-I. Relaxation and dipolar order parameters revealed enhanced microsecond dynamics due to polymer disorder in the mutants, but restricted motional amplitudes due to tighter pectin-cellulose associations. These molecular data shed light on polymer structure and packing in these two pectin mutants, helping to elucidate how pectin could influence cell wall architecture at the nanoscale, cell wall mechanics, and plant growth. • Pectin structure and cellulose packing were assessed using solid-state NMR. • Two pectin mutants, tsd2 and qua2 , were compared to wild-type Arabidopsis. • In these mutants, arabinan content is increased, with a higher degree of branching. • Mutants show tighter packing between cellulose and pectic backbones (HG and RG-I). • The motion of HG and RG-I is faster in the mutants, but with smaller amplitudes. [ABSTRACT FROM AUTHOR]