A β–glucuronosyltransferase from Arabidopsis thaliana involved in biosynthesis of type II arabinogalactan has a role in cell elongation during seedling growth

• DOI: 10.1111/tpj.12353
• Publication Date: 2013-10-15T16:04:39Z
• Authors: Eva Knoch; Adiphol Dilokpimol; Theodora Tryfona; Christian P. Poulsen; Guangyan Xiong; Jesper Harholt; Bent L. Petersen; Peter Ulvskov; Masood Z. Hadi; Toshihisa Kotake; Yoichi Tsumuraya; Markus Pauly; Paul Dupree; Naomi Geshi
• Keywords: Arabinogalactan; Galactan; Wild type; Fucosyltransferase

We have characterized a β-glucuronosyltransferase (AtGlcAT14A) from Arabidopsis thaliana that is involved in the biosynthesis of type II arabinogalactan (AG). This enzyme belongs to Carbohydrate Active Enzyme database glycosyltransferase family 14 (GT14). The protein was localized Golgi apparatus when transiently expressed Nicotiana benthamiana. soluble catalytic domain Pichia pastoris transferred glucuronic acid (GlcA) β-1,6-galactooligosaccharides with degrees polymerization (DP) ranging 3-11, and β-1,3-galactooligosaccharides DP5 7, indicating glucuronosyltransferase modifies both β-1,6- β-1,3-galactan present AG. Two allelic T-DNA insertion mutant lines showed 20-35% enhanced cell elongation during seedling growth compared wild-type. Analyses AG isolated mutants revealed reduction GlcA substitution on Gal-β-1,6-Gal β-1,3-Gal, an vivo role AtGlcAT14A synthesis those structures Moreover, relative increase levels 3-, 6- 3,6-linked galactose (Gal) reduced 2- 2,5-linked arabinose (Ara) were seen, suggesting mutation results longer branched β-1,3- β-1,6-galactans. galactosylation most likely caused by increased availability O6 position Gal, which shared acceptor site for galactosyltransferases AG, thus addition may terminate Gal chain extension. discuss biological growth.