Cell-Wall Composition and Accessibility to Hydrolytic Enzymes is Differentially Altered in Divergently Bred Switchgrass (Panicum virgatum L.) Genotypes

Abstract

The aims of this study were to understand the genotypic variability in cell-wall composition and cell-wall accessibility to enzymes in select switchgrass plants obtained from two different populations derived from a base population of octaploid cultivars. Population C+3 was developed by three breeding generations for high digestibility and population C-1 developed by one generation of breeding for low digestibility. Above-ground biomass from 12 selected genotypes, three each with high or low digestibility within each population, was analyzed for their cell-wall aromatics and polysaccharides. The ratio of p-coumaric acid/ferulic acid was greater (P < or = 0.05) for the high-lignin C-1 population over the low-lignin C+3 population, although the amounts of these two phenolics did not differ between populations. Combined values of guaiacyl + syringyl-lignin were consistently higher in genotypes from the C-1 population as compared to the genotypes from the C+3 population. Overall, p-coumaric acid was released by enzymes in greater amounts than ferulic acid in all these genotypes. Genotypes in the C-1 population exhibited lower dry weight loss as compared to the genotypes in the C+3 population after enzymatic digestion, suggesting changes in cell-wall architecture. Overall, our data highlight the phenotypic plasticity coded by the switchgrass genome and suggest that combining dry matter digestibility with other more specific cell-wall traits could result in genotypes with greater utility as bioenergy feedstocks.

Developmental Control of Lignification in Stems of Lowland Switchgrass Variety Alamo and the Effects on Saccharification Efficiency

“…8h). These results agree with the suggestion that factors affecting cell wall degradation are complex and not related to a single linkage type of wall-bound phenolic [8]. Fig.…”

“…Although several reports on genetic variability, trait relationships, and biomass production in switchgrass are now available, there is still limited information on cell wall structure and its effects on biomass saccharification efficiency. Recently, Sarath et al [8,9] reported the internode structure and cell wall composition in maturing tillers of switchgrass variety Kanlow [8] and cell wall composition and accessibility to hydrolytic enzymes in upland switchgrass genotypes [9]. In this study, we focus on cell wall biochemistry, lignin-related gene expression, and correlation between cell wall composition and saccharification efficiency of a quite different switchgrass cultivar, lowland switchgrass Alamo.…”

Plant cell wall aromatics: influence on degradation of biomass

“…Recent investigations in grass breeding have focused on the role of phenolic compounds and the eff ect of their modifi cation for improved utilization . 28,53 Preliminary studies using phenolic acid esterases for pretreatment suggest that enzyme strategies could be developed to maximize sugars and aromatic coproducts from grass feedstocks. Cereal brans particularly may provide one of the most advantageous opportunities, since brans are already collected at the milling site, can complement sugar levels of grain for increased ethanol production, and are the richest source of phenolic acids.…”

Dedicated Herbaceous Biomass Feedstock Genetics and Development

“…Taking a subset of plants with the highest or lowest stem lignin from each of two populations, significant differences were noticed in the overall compositional makeup of total plant biomass comprised of stems and leaves. As the first report of this kind for switchgrass, it was possible to show that cell wall accessibility to cellulases was modified in these plants [12,88]. In a follow-up study, using only stems obtained from these octaploid plants, the importance of cell wall architecture on final ethanol yields was established.…”