Cellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1A903V and CESA3T942I of cellulose synthase

D.M. HARRIS, K. CORBIN, J.K.C. ROSE, A.L. BERTOLO, T. WANG, D. SMILGIES, R. GUTIERREZ, J. STORK, J. M. ESTEVEZ, C.A. PETTI, D. BONETTA, C. SOMERVILLE, M. HONG & S. DEBOLT

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2012 vol. 109 p. 4099 - 4103

0027-8424

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 islinked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, whichcould 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 CESA1A903V and CESA3T942I in Arabidopsis thaliana. Using 13C solidstate nuclear magnetic resonance spectroscopy and X-ray diffraction, we show that the cellulose microfibrils displayed reducedwidth 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 CESA1A903V and CESA3T942I displayed greater saccharification efficiency than wild type. Using live-cell imaging to track fluorescentlylabeled 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 CESA1A903V and CESA3T942I have modified microfibril structure in terms of crystallinityand suggest that in plants, as in bacteria, crystallization biophysically limits polymerization.