Cellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1 A ?°³ V and CESA3 T ?4² I of cellulose synthase

DM Harris, Kendall Corbin, Tuo Wang, Ryan Gutierrez, Ana Bertolo, Carloalberto Petti, Detlef-M. Smilgies, José Estevez, Dario Bonetta, Breeanna Urbanowicz, David Ehrhardt, Chris Somerville, Jocelyn Rose, Mei Hong, Seth DeBolt

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    Abstract

    The mechanisms underlying the biosynthesis of cellulose in plants are complex and still poorly understood. A central question concerns the mechanism of microfibril structure and how this is linked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, which could be transformative in a bio-based economy. To explore these processes in planta, we developed a chemical genetic toolbox of pharmacological inhibitors and corresponding resistance-conferring point mutations in the C-terminal transmembrane domain region of CESA1 A903V and CESA3 T942I in Arabidopsis thaliana. Using 13C solidstate nuclear magnetic resonance spectroscopy and X-ray diffraction, we show that the cellulose microfibrils displayed reduced width and an additional cellulose C4 peak indicative of a degree of crystallinity that is intermediate between the surface and interior glucans of wild type, suggesting a difference in glucan chain association during microfibril formation. Consistent with measurements of lower microfibril crystallinity, cellulose extracts from mutated CESA1 A903V and CESA3 T942I displayed greater saccharification efficiency than wild type. Using live-cell imaging to track fluorescently labeled CESA, we found that these mutants show increased CESA velocities in the plasma membrane, an indication of increased polymerization rate. Collectively, these data suggest that CESA1 A903Vand CESA3 T942I have modified microfibril structure in terms of crystallinity and suggest that in plants, as in bacteria, crystallization biophysically limits polymerization.

    Original languageEnglish
    Pages (from-to)4098-4103
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume109
    Issue number11
    DOIs
    Publication statusPublished - 2012

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    Harris, DM., Corbin, K., Wang, T., Gutierrez, R., Bertolo, A., Petti, C., Smilgies, D-M., Estevez, J., Bonetta, D., Urbanowicz, B., Ehrhardt, D., Somerville, C., Rose, J., Hong, M., & DeBolt, S. (2012). Cellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1 A ?°³ V and CESA3 T ?4² I of cellulose synthase. Proceedings of the National Academy of Sciences of the United States of America, 109(11), 4098-4103. https://doi.org/10.1073/pnas.1200352109