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Visualization of cellulose synthases in Arabidopsis secondary cell walls

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Science  09 Oct 2015:
Vol. 350, Issue 6257, pp. 198-203
DOI: 10.1126/science.aac7446

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Secondary cell walls built with speed

Plant cell walls provide the cellulose that is integral for wood, cotton fiber, and many biofuels. Cellulose is synthesized outside the cell membrane by cellulose synthase enzymes. Much of the secondary cell wall, responsible for the sturdiness of wood, is formed by xylem cells embedded in the core of the plant. Watanabe et al. leveraged ectopic expression to bring xylem-style cellulose synthase activity to the epidermal surface of the plant (see the Perspective by Schneider and Persson). Combining this improved accessibility with fluorescent tagging showed that secondary cell walls are built faster than primary cell walls, perhaps due to increased velocity and density of cellulose synthase complexes.

Science, this issue p. 198, see also p. 156

Abstract

Cellulose biosynthesis in plant secondary cell walls forms the basis of vascular development in land plants, with xylem tissues constituting the vast majority of terrestrial biomass. We used plant lines that contained an inducible master transcription factor controlling xylem cell fate to quantitatively image fluorescently tagged cellulose synthase enzymes during cellulose deposition in living protoxylem cells. The formation of secondary cell wall thickenings was associated with a redistribution and enrichment of CESA7-containing cellulose synthase complexes (CSCs) into narrow membrane domains. The velocities of secondary cell wall–specific CSCs were faster than those of primary cell wall CSCs during abundant cellulose production. Dynamic intracellular of endomembranes, in combination with increased velocity and high density of CSCs, enables cellulose to be synthesized rapidly in secondary cell walls.

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