CELLULAR & MOLECULAR BIOLOGY LETTERS Volume 9, (2004) pp 935 – 946 http://www.cmbl.org.pl Received 22 September 2004 Accepted 18 November 2004 * Corresponding author, e-mail: szopa@ibmb.uni.wroc.pl , tel: (4871) 3756202, fax: (4871) 3252930 GLUCOSYLTRANSFERASE: THE GENE ARRANGEMENT AND ENZYME FUNCTION KATARZYNA LORENC-KUKUŁA 1 , ALINA KOROBCZAK 1 , ANNA AKSAMIT-STACHURSKA 2 , KAMIL KOSTYŃ 1 , MARCIN ŁUKASZEWICZ 2 and JAN SZOPA 1 * 1 Institute of Biochemistry and Molecular Biology, 2 Institute of Genetics and Microbiology, University of Wrocław, Przybyszewskiego 63/77, 51-148 Wrocław, Poland Abstract: Glucosyltransferases were isolated and characterised from many plant sources. The enzymes show middle amino acid similarity and broad substrate specificity. The promoter of the potato 5-UGT gene reveals strong environmental induction. The activation of the gene expression by UV radiation, ABA and cold treatments was detected. Overexpression of 5-UGT resulted in the accumulation of the diglucoside derivative of petunidin in transgenic tubers; the latter is most probably the reason for plant resistance to pathogen infection. Overexpressing plants produced more tubers, and the overall yield was higher when compared to nontransformants. Key Words: Glucosylation, Anthocyanin, Glucosyltransferase Gene INTRODUCTION Glucosylation is a prominent modification reaction in the plant metabolism. The targets of this modification are often secondary metabolites [1]. In many cases, glucosylation is the last step in the biosynthesis of a number of secondary plant products including flavonoids, cyanohydrins, steroidal alkaloids and saponins [2]. More than 6,000 different glucosidic derivatives have already been identified and described [3]. Glucosylation mainly occurs on oxygen (COOH- and OH-), sulphur, nitrogen and carbon atoms provided by nucleotide-activated sugar acting as a donor substrate [4]. The transfer of a nucleotide-diphosphate- activated monosaccharide unit (glucose, rhamnose, galactose, xylose, rutinose, and neohesperidose) [5] to an acceptor molecule is catalysed by glucosyltransferases (UGTs). This modification often leads to changes in the