Genomic characterization and physical mapping of two fucosyltransferase genes inMedicago truncatula

Abstract

Fucosyltransferases catalyse fucose transfer onto oligosaccharides. Two fucosylated structures have been identified in plants: the alpha1,4-fucosylated Lewis-a epitope and the alpha1,3-fucosylated core. Here we report the cloning, genomic characterization, and physical mapping of two genes encoding proteins similar to alpha1,4-fucosyltransferase (EC 2.4.1.65, MtFUT1) and alpha1,3-fucosyltransferase (EC 2.4.1.214, MtFUT2) in Medicago truncatula. Analysis of the genomic organization of the fucosyltransferase genes in M. truncatula, revealed the presence of two genomic variants of the MtFUT1 gene coding sequence, one containing a single intron and the other intronless, whereas in MtFUT2, the gene coding region is interrupted by four introns. Using for the first time fluorescence in situ hybridization (FISH) to physically map fucosyltransferase genes in plants, this study reveals a high genomic dispersion of these genes in Medicago. The MtFUT1 genes are mapped on chromosomes 4, 7, and 8, colocalizing on three of the five MtFUT2 loci. Chromosomes 1 and 5 carry the additional MtFUT2 loci. Moreover, the intensity of the FISH signals reveals marked differences in the number of gene copies per locus for both genes. Simultaneous mapping of rRNA genes on chromosome 5 shows that several MTFUT2 gene loci are inserted within the rDNA array. Insertions of coding DNA sequences into the rDNA repeats were never reported to date.

Down‐regulated expression of plant‐specific glycoepitopes in alfalfa

“…Both amino acid sequences contain three potential N ‐glycosylation sites: Asn242, Asn342 and Asn425 for MsFTa; Asn241, Asn341 and Asn424 for MsFTb (Figure 1a). The amino acid sequences of MsFTa and MsFTb present 80%, 68%, 58% and 95% identity with α1,3‐FTs from V. radiata , A. thaliana , P. patens and M. truncatula , respectively (Leiter et al ., 1999; Bakker et al ., 2001b; Wilson et al ., 2001; Koprivova et al ., 2004; Castilho et al ., 2005), the higher sequence homologies being observed in the luminal regions of these glycosyltransferases. Sequence analysis of this highly conserved luminal region of MsFTa and MsFTb cDNAs revealed the presence of motif II and a CXXC motif (Figure 1b), which are conserved in plant and mammalian FTs of the GT14 family in the CAZy database (Carbohydrate‐Active enzymes; http://www.cazy.org/; Bakker et al ., 2001b; Fabini et al ., 2001; Wilson et al ., 2001; Leonard et al ., 2002; Coutinho et al ., 2003; Dupuy et al ., 2004).…”