Moss cell walls: structure and biosynthesis

Abstract

The genome sequence of the moss Physcomitrella patens has stimulated new research examining the cell wall polysaccharides of mosses and the glycosyl transferases that synthesize them as a means to understand fundamental processes of cell wall biosynthesis and plant cell wall evolution. The cell walls of mosses and vascular plants are composed of the same classes of polysaccharides, but with differences in side chain composition and structure. Similarly, the genomes of P. patens and angiosperms encode the same families of cell wall glycosyl transferases, yet, in many cases these families have diversified independently in each lineage. Our understanding of land plant evolution could be enhanced by more complete knowledge of the relationships among glycosyl transferase functional diversification, cell wall structural and biochemical specialization, and the roles of cell walls in plant adaptation. As a foundation for these studies, we review the features of P. patens as an experimental system, analyses of cell wall composition in various moss species, recent studies that elucidate the structure and biosynthesis of cell wall polysaccharides in P. patens, and phylogenetic analysis of P. patens genes potentially involved in cell wall biosynthesis.

A single heterologously expressed plant cellulose synthase isoform is sufficient for cellulose microfibril formation in vitro

“…The strong interaction of cellulose synthase with the nascent cellulose polymer is exemplified by Rhodobacter BcsA, which, upon heterologous expression in E. coli and detergent solubilization, copurifies with a cellulose chain (7). The width of the fibril-attached particle is consistent with size estimates for plant CesA oligomers, referred to as "rosettes," observed by freeze-fracture EM (11,29,30). CesA rosettes have recently been interpreted as hexamers of CesA trimers, yielding a total of 18 CesA molecules per complex and, accordingly, a maximum of 18 glucan chains per cellulose microfibril (31,32).…”

Temporal separation between CO2 assimilation and growth? Experimental and theoretical evidence from the desiccation‐tolerant moss Syntrichia ruralis

“…If the desiccation persists then an optimal concentration of compatible solutes will be synthesized to ensure adequate protection of the metabolic apparatus and DNA during the quiescent period until wet conditions return. As the growth rate of moss is slow it is likely that genetic studies will be required to confirm exactly when during the rewetting and drying cycle of mosses cellulose synthesis takes place (Roberts et al, 2012).…”

An alternative model for the earliest evolution of vascular plants

“…Unthickened water‐conducting cells are typical of mosses (Roberts et al . ). They can be also observed in Aglaophyton (Fig.…”