Molecular cloning and functional expression of β1,2‐xylosyltransferase cDNA from Arabidopsis thaliana¹

The transfer of xylose from UDP-xylose to the core beta-linked mannose of N-linked oligosaccharides by beta1,2-xylosyltransferase (XylT) is a widespread feature of plant glycoproteins which renders them immunogenic and allergenic in man. Here, we report the isolation of the Arabidopsis thaliana XylT gene, which contains two introns and encodes a 60.2 kDa protein with a predicted type II transmembrane protein topology typical for Golgi glycosyltransferases. Upon expression of A. thaliana XylT cDNA in the baculovirus/insect cell system, a recombinant protein was produced that exhibited XylT activity in vitro. Furthermore, the recombinant enzyme displayed XylT activity in vivo in the insect cells, as judged by the acquired cross-reaction of cellular glycoproteins with antibodies against the beta1,2-xylose epitope. The cloned XylT cDNA as well as the recombinant enzyme are essential tools to study the role of beta1,2-xylose in the immunogenicity and allergenicity of plant glycoproteins at the molecular level.