Regulation of cellulose synthase assembly and cellulose microfibril structure

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Cellulose, the major polysaccharide of the plant cell wall, provides strength to plant cell walls and is the most abundant organic polymer on Earth. Its application in everyday life is widespread, exemplified by our large-scale use of cotton, paper and timber. Yet there are many aspects of cellulose biology and cellulose structure that are not understood. Cellulose forms crystalline microfibrils that are embedded in walls of other polysaccharides, primarily xylan and glucomannan, plus lignin. The mechanism of interaction of cellulose microfibrils with the hemicelluloses in the secondary plant cell wall is not well understood, but this team recently showed, using solid-state NMR of Arabidopsis and mutants, that xylan and cellulose assemble in the wall through complementarity of their shapes.
We recently discovered STELLO, a Golgi-localised putative glycosyltransferase, that is important for correct cellulose fibril synthesis. STELLO appears to regulate cellulose synthase complex assembly and trafficking. This discovery reveals an unexpected regulation of the cellulose synthesis machinery through an unknown glycosylation process in the plant Golgi apparatus. In this program of research, we will study the defective cellulose in the stl mutants using a new and robust solid-state NMR technique applied in our team to intact plant secondary cell walls. Preliminary evidence suggests that the cellulose fibrils are defective in shape such that xylan cannot bind in the normal way, disrupting cell wall assembly. We will investigate further the hypothesis that STELLO is a glycosyltransferase that glycosylates cellulose synthesis proteins (CESAs). We will study how assembly and trafficking of the cellulose synthesis complex is affected by loss of STELLO protein and mutation of STELLO glycosylation activity. Through this research, we aim to reveal how a process of Golgi glycosylation regulates cellulose synthase assembly and cellulose microfibril structure.

Impact summary

Impact goals: The research team recognizes that both in the UK and globally we face significant challenges in producing sustainable and cost-effective materials from plant biomass. We aim to assist industry in development of sustainable biomass applications. We also aim to inform the public about the scientific basis of timber strength, the molecular basis of wood and paper, and also the applications of renewable plant materials. Additionally we aim to inspire children and school pupils to study and appreciate plant science as a way to promote sustainable materials of the future.

Industry stakeholders.
-Paper and pulp industry, through better understanding of timber and pulping processes (Stora Enso).
-Forestry companies through better breeding strategies, and better wood analysis techniques (Scion, New Zealand, and Innventia (RISE), Sweden).
-Timber for building construction through understanding wood processing, such as acetylation (Accoya, Stora Enso).
-Biorefining industry through better understanding of enzyme substrates (Novozymes).
-Cellulosic bioenergy industry though better process development for saccharification of sugar cane bagasse (Granbio, Brazil)
-Advanced biomaterials industry (various companies via Wallenberg Wood Science Centre).
-Crop breeders interested to reduce lodging and increase forage digestibility.

Society stakeholders.
-Local and national public and school children attending outreach events (Cambridge Science week events March annually, Cambridge Fascination of plants in Botanic Garden, May annually, Royal Society London Science Week)
-Children and school pupils will be inspired to study and value plant science and sustainable renewable materials.

To achieve these goals we will follow our pathways to impact plan.