Research article Up-regulated transcripts in a compatible powdery mildew–grapevine interaction Csaba Fekete a, c , Raymond W.M. Fung a , Zolta ´ n Szabo ´ d , Wenping Qiu a , Le Chang a , Daniel P. Schachtman b , La ´ szlo ´ G. Kova ´ cs a, * a Department of Agriculture, Missouri State University, Mountain Grove, MO 65711, USA b The Donald Danforth Plant Science Center, St. Louis, MO 63132, USA c Department of General and Environmental Microbiology, University of Pe ´cs, H-7624 Pe ´cs, Hungary d Genetics and Plant Biotechnology Institute, Szent Istva ´n University, H-2103 Go ¨do ¨llo ¨, Hungary article info Article history: Received 8 October 2008 Accepted 14 March 2009 Available online 25 March 2009 Keywords: Defense Grapevine Powdery mildew Susceptibility Transcription abstract Powdery mildews (Erysiphales) are obligate biotrophic pathogens that invade susceptible plant cells without triggering cell death. This suggests a highly adept mechanism of parasitism which enables powdery mildews to avoid detection or evade defenses by their host. To better understand this plant– pathogen interaction, we employed suppression subtractive hybridization (SSH), differential hybridiza- tion and quantitative real-time (qRT) PCR for the identification of grapevine (Vitis vinifera L.) genes that were specifically up-regulated in response to the grape powdery mildew Erysiphe necator Schwein. We identified 25 grapevine transcripts that increased in abundance upon infection in leaves of the susceptible host V. vinifera Cabernet Sauvignon. Despite the compatible interaction between the path- ogen and plant, several of the E. necator-induced transcripts represented typical defense response genes. Among the transcripts identified were those that encoded a leucine-rich repeat serine/threonine kinase- like receptor, an MYB transcription factor, and two ubiquitination-associated proteins, indicating the stimulation of intracellular signal transduction and regulatory functions. A number of genes character- istic of senescence processes, including metallothioneins, a deoxyribonuclease, an aspartyl protease and a subtilase-like serine protease, also were identified. These transcripts expanded the list of previously identified E. necator-responsive grapevine genes and facilitated a more comprehensive view of the molecular events that underlie this economically important plant–pathogen interaction. Ó 2009 Elsevier Masson SAS. All rights reserved. 1. Introduction Powdery mildews (PMs) are obligate plant pathogenic fungi of the order Erysiphales which includes a broad range of genera and species. Each PM species is pathogenic on a well-defined range of plants. Erysiphe necator Schwein causes PM disease on members of the Vitaceae family. E. necator is highly virulent on most varieties of the cultivated grapevine and, therefore, it represents a major agricultural problem worldwide. A recent series of studies in Arabidopsis greatly advanced our understanding of the host–pathogen specificity of PMs and their hosts. Arabidopsis mutants in which a gene for a syntaxin (PEN1), a peroxisome-associated glycosyl hydrolase (PEN2), or an ABC transporter (PEN3) was inactivated, allowed initial invasion by the non-adapted PM species B. graminis f. sp. hordei and E. pisi [5,18,29]. Disease development in these mutants, however, was arrested during the initial stages of infection by hypersensitive-like death of the invaded cells, indicating the existence of a second line of defense against PM. This second line of defense could be broken by the mutational inactivation of two key genes of the salicylic acid- mediated signal transduction pathway, PAD4 and SAG101 [18]. While salicylic acid-regulated and PEN genes obstruct ingress by the PM fungus, other host genes are required for the establishment of the parasitic relationship between the fungus and the plant. In barley and tomato, for example, a member of the Mlo gene family is required for adapted PM pathogens to invade these hosts [1,4]. The Mlo genes encode integral membrane proteins which are likely to be involved in vesicle transport-related events at the plasma membrane. Additional host genes required for PM invasion have Abbreviations: PM, powdery mildew; SSH, suppression subtractive hybridiza- tion; qRT-PCR, quantitative real-time polymerase chain reaction; hpi, hours post- inoculation; AISL, all-stages infection subtracted library; EISL, early-stage infection subtracted library; LISL, late-stage infection subtracted library; EST, expressed sequence tag; NCBI, National Center for Biotechnology Information; LRR, leucine- rich repeat PR-1, pathogenesis-related protein-1; UPS, ubiquitin/proteasome system; MT, metallothionein. * Corresponding author. Missouri State University, 9740 Red Spring Road, Mountain Grove, MO 65711, USA. Tel.: þ1 417 547 7524; fax: þ1 417 547 7540. E-mail address: laszlokovacs@missouristate.edu (L.G. Kova ´ cs). Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy 0981-9428/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.plaphy.2009.03.006 Plant Physiology and Biochemistry 47 (2009) 732–738