Please cite this article in press as: Ruocco M, et al. Four potato (Solanum tuberosum) ABCG transporters and their expression in response to abiotic factors and Phytophthora infestans infection. J Plant Physiol (2011), doi:10.1016/j.jplph.2011.07.008 ARTICLE IN PRESS G Model JPLPH-51322; No. of Pages 9 Journal of Plant Physiology xxx (2011) xxx–xxx Contents lists available at SciVerse ScienceDirect Journal of Plant Physiology jou rn al h o mepage: www.elsevier.de/jplph Four potato (Solanum tuberosum) ABCG transporters and their expression in response to abiotic factors and Phytophthora infestans infection Michelina Ruocco a,∗ , Patrizia Ambrosino b , Stefania Lanzuise b , Sheridan Lois Woo b , Matteo Lorito b , Felice Scala b a Istituto per la Protezione delle Piante CNR, Via Università 133, 80055 Portici (NA), Italy b Dipartimento di Arboricoltura Botanica e Patologia vegetale, Via Università 100, 80055 Portici (NA), Italy a r t i c l e i n f o Article history: Received 3 May 2011 Received in revised form 12 July 2011 Accepted 21 July 2011 Keywords: Stress response ABC transporters Plant–microbe interactions Potato Phytophthora infestans a b s t r a c t Pleiotropic drug resistant (PDR/ABCG) genes are involved in plant response to biotic and abiotic stresses. In this work, we cloned, from Solanum tuberosum, four PDR/ABCG transporter genes named StPDR1, StPDR2, StPDR3 and StPDR4, which were differentially expressed in plant tissues and cell cultures. A number of different chemically unrelated compounds were found to regulate the transcript levels of the four genes in cultured cells. In particular, StPDR2 was highly up-regulated in the presence of Botrytis cinerea cell walls, NaCl, 2,4-dichlorophenol, sclareol and -solanin and biological compounds. The expression of the genes was also investigated by real time RT-PCR during infection by Phytophthora infestans. StPDR1 and StPDR2 were up-regulated about 13- and 37-fold at 48 h post-infection (hpi), StPDR3 was expressed (4–5-fold) at 24 and 48 hpi and then rapidly decreased, while StPDR4 RNA accumulation was stimulated (about 4-fold) at 12 and 24 hpi, decreased at 48 hpi and increased again at 96 hpi. We discuss the role of StPDR1–4 genes in response to pathogens and abiotic stresses. © 2011 Elsevier GmbH. All rights reserved. Introduction The ATP-binding cassette (ABC) transporter superfamily con- sists of a large group of related proteins whose members have been implicated in the active movement of a variety of substances across cellular membranes in organisms ranging from bacteria to man (Higgins, 2001). These proteins typically contain two core structural elements: a hydrophobic transmembrane domain (TMD) consist- ing of multiple membrane spanning segments (usually six), and a hydrophilic nucleotide binding fold (NBF) containing the Walker A, Walker B and ABC signature (Rea, 2007; Walker et al., 1982). ABC transporters have been reported to occur both as “half size,” which contain of one hydrophobic and one hydrophilic domain, and as “full size”, with two domains each (Verrier et al., 2008). Plants have a large number of ABC proteins that may be associ- ated with the movement of a variety of secondary metabolites. In the absence of a specialized secretor structure, plants need to estab- lish steep concentration gradients to allow the movement of solutes across cellular membranes (Verrier et al., 2008; Yazaki et al., 2006). The sequencing of Arabidopsis thaliana and Oryza sativa genomes led to the identification of more than 120 genes encoding ABC trans- porters (Garcia et al., 2004; Lee et al., 2005; Sanchez-Fernandez ∗ Corresponding author. Tel.: +39 081 2539337; fax: +39 081 2539339. E-mail address: ruocco@ipp.cnr.it (M. Ruocco). et al., 2001), while only 50–70 ABC-proteins have been found in the genome of humans, fly (Drosophila melanogaster) and worm (Caenorhabditis elegans) (Rea, 2007). Because ABC transporters are involved in cellular detoxification, chlorophyll biosynthesis, stomata opening and closing, they can play a direct or indirect role in plant growth and developmental processes (Klein et al., 2004; Luo et al., 2007; Martinoia et al., 2002; Ticconi et al., 2009; Titapiwatanakun and Murphy, 2009; Zientara et al., 2009). Plant ABC proteins are divided into 13 subfamilies on the basis of protein size (full, half, or quarter molecules), orientation of TMD and NBF domains, presence or absence of idiotypic trans- membrane and/or linker domains, and overall sequence similarity. Some of the best characterized subfamilies are multidrug resistance proteins (MDR/ABCB), multidrug resistance-associated proteins (MRP/ABCC), pleiotropic drug resistance proteins (PDR/ABCG) and peroxisomal membrane proteins (PMP/ABCD) (for reviews see: Rea, 2007; Sanchez-Fernandez et al., 2001; Verrier et al., 2008). The PDR/ABCG subfamily is encoded by more than 15 ORFs in Arabidopsis (Jasinski et al., 2003; Sanchez-Fernandez et al., 2001; van den Brule and Smart, 2002) and 23 in rice (Crouzet et al., 2006). Genes encoding for PDR/ABCG homologues have not been identified in animal and prokaryotes, but only in yeasts, fungi and plants. Interest in PDR/ABCG transporters has been particularly stimulated by their involvement in the extrusion of cytotoxic com- pounds. In fungi, PDR/ABCG transporters have been associated with 0176-1617/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.jplph.2011.07.008