Abstract
Sheepgrass (Leymus chinensis) is a high-quality cool-season forage crop used as pasture and hay for livestock feeds. The presence of lignin in cell walls, however, impairs forage digestibility of such lignocellulosic feedstock. Here, the structural characterization and cell wall composition of sheepgrass internodes were studied, and a progressive increase in cell wall lignification was observed with internode maturation. Lignin composition analysis further revealed a gradual accumulation of guaiacyl and syringyl lignin units during internode development. Consistently, the transcript abundance of lignin-related genes was upregulated in mature internodes, suggesting their potential roles in lignin biosynthesis. Furthermore, the effects of cell wall composition and lignification extent on biomass saccharification efficiency were examined in sheepgrass. The results showed that lignin content, guaiacyl and syringyl lignin unit levels inversely correlated with cell wall digestibility, indicating that lignin is a crucial obstacle for utilizing sheepgrass feedstock. The baseline information obtained in this work will facilitate establishment, grazing management, harvesting and feedstock utilization of sheepgrass in future.
Highlights
Sheepgrass (Leymus chinensis) is an important C3 perennial cool-season forage grass widely distributing on the eastern Eurasian steppe (Bai et al, 2004)
The results showed that the structural features, lignin-related gene expression profiles, and lignification patterns of internodes were significantly altered with internode maturation in sheepgrass
Based on the nomenclature of tiller stages described by Moore et al (1991), we divided the life cycle of sheepgrass tillers into vegetative, elongation, reproductive, and seed ripening stages, which are associated with a progressive lignification of cell walls (Figure 1)
Summary
Sheepgrass (Leymus chinensis) is an important C3 perennial cool-season forage grass widely distributing on the eastern Eurasian steppe (Bai et al, 2004). The tender tillers of sheepgrass are rich in cellulose, hemicellulose, and soluble proteins that can be utilized as a high-quality feedstock for ruminant animals such as cattle and sheep (Chen et al, 2015). Because of the economic importance of sheepgrass, the utilization and improvement of sheepgrass feedstocks have been broadly studied during the past decades (Chen et al, 2002, 2015; Wang et al, 2009). It has been indicated that cell wall lignification extent of feedstock is one of the major factors influencing forage digestibility (Chen et al, 2002; Chen and Dixon, 2007). The structural and compositional elucidation of sheepgrass internodes will provide a baseline understanding of relationships between cell wall lignification and digestibility
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