OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 19/7/2278    most recent tpc.107.052985v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Strasser, R. Articles by Mach, L. Search for Related Content PubMed PubMed Citation Articles by Strasser, R. Articles by Mach, L. Agricola Articles by Strasser, R. Articles by Mach, L.

A Unique ß1,3-Galactosyltransferase Is Indispensable for the Biosynthesis of N-Glycans Containing Lewis a Structures in Arabidopsis thaliana^[W],[OA]

^a Institute of Applied Genetics and Cell Biology, BOKU, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria
^b Department of Chemistry, BOKU, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria

¹ Address correspondence to richard.strasser{at}boku.ac.at.

In plants, the only known outer-chain elongation of complex N-glycans is the formation of Lewis a [Fuc1-4(Galß1-3)GlcNAc-R] structures. This process involves the sequential attachment of ß1,3-galactose and 1,4-fucose residues by ß1,3-galactosyltransferase and 1,4-fucosyltransferase. However, the exact mechanism underlying the formation of Lewis a epitopes in plants is poorly understood, largely because one of the involved enzymes, ß1,3-galactosyltransferase, has not yet been identified and characterized. Here, we report the identification of an Arabidopsis thaliana ß1,3-galactosyltransferase involved in the biosynthesis of the Lewis a epitope using an expression cloning strategy. Overexpression of various candidates led to the identification of a single gene (named GALACTOSYLTRANSFERASE1 [GALT1]) that increased the originally very low Lewis a epitope levels in planta. Recombinant GALT1 protein produced in insect cells was capable of transferring ß1,3-linked galactose residues to various N-glycan acceptor substrates, and subsequent treatment of the reaction products with 1,4-fucosyltransferase resulted in the generation of Lewis a structures. Furthermore, transgenic Arabidopsis plants lacking a functional GALT1 mRNA did not show any detectable amounts of Lewis a epitopes on endogenous glycoproteins. Taken together, our results demonstrate that GALT1 is both sufficient and essential for the addition of ß1,3-linked galactose residues to N-glycans and thus is required for the biosynthesis of Lewis a structures in Arabidopsis. Moreover, cell biological characterization of a transiently expressed GALT1-fluorescent protein fusion using confocal laser scanning microscopy revealed the exclusive location of GALT1 within the Golgi apparatus, which is in good agreement with the proposed physiological action of the enzyme.

This article has been cited by other articles:

				J. S. Kang, J. Frank, C. H. Kang, H. Kajiura, M. Vikram, A. Ueda, S. Kim, J. D. Bahk, B. Triplett, K. Fujiyama, et al. Salt tolerance of Arabidopsis thaliana requires maturation of N-glycosylated proteins in the Golgi apparatus PNAS, April 15, 2008; 105(15): 5933 - 5938. [Abstract] [Full Text] [PDF]