Cell wall compositional modifications of Miscanthus ecotypes in response to cold acclimation

The cell wall composition of three Miscanthus clones with contrasted frost tolerance has been determined during cold acclimation. The plants were harvested at the juvenile stage and cell wall composition of each clone during cold acclimation was compared to the one of non cold-treated plants. [Display omitted] ► PAL activity was increased in the frost-tolerant Miscanthus clones under cold stress. ► CAD activity under cold stress was largest in the frost-tolerant clones. ► During cold acclimation, an increase in β-glucan was observed in all genotypes. ► GAX content changed in the frost tolerant clones under the ambient conditions. Miscanthus, a potential energy crop grass, can be damaged by late frost when shoots emerge too early in the spring and during the first winter after planting. The effects of cold acclimation on cell wall composition were investigated in a frost-sensitive clone of Miscanthus x giganteus compared to frost-tolerant clone, Miscanthus sinensis August Feder, and an intermediate frost-tolerant clone, M. sinensis Goliath. Cellulose and lignin contents were higher in M. x giganteus than in the M. sinensis genotypes. In ambient temperature controls, each clone displayed different glucuronoarabinoxylan (GAX) contents and degree of arabinose substitution on the xylan backbone. During cold acclimation, an increase in (1→3),(1→4)-β-d-glucan content was observed in all genotypes. Uronic acid level increased in the frost sensitive genotype but decreased in the frost tolerant genotypes in response to cold. In all clones, major changes in cell wall composition were observed with modifications in phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) activities in both non- and cold-acclimated experiments. A large increase in CAD activity under cold stress was displayed in each clone, but it was largest in the frost-tolerant clone, M. sinensis August Feder. The marked increase in PAL activity observed in the frost-tolerant clones under cold acclimation, suggests a reorientation of the products towards the phenylpropanoid pathway or aromatic synthesis. How changes in cell wall physical properties can impact frost tolerance is discussed.