The potato glucosyltransferase gene promoter is environmentally regulated Alina Korobczak a , Anna Aksamit b , Marcin Lukaszewicz b , Katarzyna Lorenc a , Tadeusz Rorat c , Jan Szopa a, * a Institute of Biochemistry and Molecular Biology, Wroclaw University, Przybyszewskiego 63/77, 51-148 Wroclaw, Poland b Institute of Genetics and Microbiology, Wroclaw University, Przybyszewskiego 63/77, 51-148 Wroclaw, Poland c Institute of Plant Genetics PAS, Strzeszyn ´ska 34, 60-479 Poznan ´, Poland Received 22 July 2004; accepted 30 July 2004 Available online 8 September 2004 Abstract Anthocyanidine glucosyltransferase (GT) is a key upregulating enzyme in anthocyanins stability. A 1.6 kb-GT promoter from Solanum sogarandinum has been isolated and its sequence analysed. The inspection of the promoter sequence revealed several boxes important for the regulation of gene expression. The motifs arrangement was studied using transgenic potato plants transformed with a GT promoter-b- glucuronidase gene fusion construct. The exposure of the transgenic potato to UV, cold, light, as well as the salt and ABA treatment resulted in 5.5-, 6-, 5-, 5- and 8-fold increase in enzyme activity, respectively. The synergistic mode of cold-light and ABA-cold effect has been detected. The UV and cold inducibility of promoter implicates its upregulatory function in flavonoid stability and thus the regulatory role in plant protection against abiotic stresses. In turn, the increase in sucrose concentration (over 2%) in growth medium inhibits GT promoter driven GUS activity. The changes in GT promoter activity upon treatment was confirmed in most cases by western analysis of unmodified plant treated in the same way. The only difference was NaCl treatment that resulted in unchanged GT protein level. Histochemical analysis of GUS under GT promoter revealed the cell specific expression. In leaves the highest expression has been detected in epidermis and spongy mesophyll, but weak staining signals were visible also in other leaf tissues. This pattern became more pronounced in leaves treated with UV. Stem tissues did not show any GUS activity, while in tubers the GUS staining was observed in cortex under periderm and in vascular ring. In roots staining was localized in the root hair zone where rhizodermis and cortex cells are stained. # 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Glucosyltransferase gene; Promoter analysis; GUS staining; Solanum sogarandinum 1. Introduction Numerous recent investigations suggest that plant response to UV irradiation, low temperature and many other abiotic stresses lead to the synthesis of protective compounds [1–4]. Among the accumulated stress response metabolites the anthocyanidins represent the majority. Aglicones are glucosylated, which results in the formation of more stable anthocyanins [5]. It is now fairly well established that glucosylation occurs in two stages. The first stage is the transfer of the glucosyl moiety from UDP- glucose to the 3-hydroxyl group of anthocyanidin, and has been first shown in cell cultures of Haplopappus gracilis [6] and in seedlings of Brassica oleracea [7] and maize [8]. In the next stage, the anthocyanins are the target of 5-O- glucosyltransferase (GT), an enzyme transferring the glucose to the 5-position [8]. This modification is an important step in the anthocyanin biosynthesis pathway producing stable anthocyanins complexes involved in www.elsevier.com/locate/plantsci Plant Science 168 (2005) 339–348 Abbreviations: ABA, abscisic acid; GUS, b-glucuronidase; GT, glucosyltransferase * Corresponding author. Tel.: +48 71 3756202; fax: +48 71 3252930. E-mail address: szopa@ibmb.uni.wroc.pl (J. Szopa). 0168-9452/$ – see front matter # 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2004.07.038