title: Membrane transporters in self resistance of Cercospora nicotianae to the photoactivated toxin cercosporin.
abstract: The goal of this work is to characterize membrane transporter genes in Cercospora fungi required for autoresistance to the photoactivated, active-oxygen-generating toxin cercosporin they produce for infection of host plants. Previous studies implicated a role for diverse membrane transporters in cercosporin resistance. In this study, transporters identified in a subtractive cDNA library between a Cercospora nicotianae wild type and a cercosporin-sensitive mutant were characterized, including two ABC transporters (CnATR2, CnATR3), an MFS transporter (CnMFS2), a uracil transporter, and a zinc transport protein. Phylogenetic analysis showed that only CnATR3 clustered with transporters previously characterized to be involved in cercosporin resistance. Quantitative RT-PCR analysis of gene expression under conditions of cercosporin toxicity, however, showed that only CnATR2 was upregulated, thus this gene was selected for further characterization. Transformation and expression of CnATR2 in the cercosporin-sensitive fungus Neurospora crassa significantly increased cercosporin resistance. Targeted gene disruption of CnATR2 in the wild type C. nicotianae, however, did not decrease resistance. Expression analysis of other transporters in the cnatr2 mutant under conditions of cercosporin toxicity showed significant upregulation of the cercosporin facilitator protein gene (CFP), encoding an MFS transporter previously characterized as playing an important role in cercosporin autoresistance in Cercospora species. We conclude that cercosporin autoresistance in Cercospora is mediated by multiple genes, and that the fungus compensates for mutations by up-regulation of other resistance genes. CnATR2 may be a useful gene, alone or in addition to other known resistance genes, for engineering Cercospora resistance in crop plants.
authors: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA.
authors: Aydin
authors: A
authors: Beseli
authors: National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Paholyothin Rd. Klong 1, Klong Luang, Pathumthani, 12120, Thailand.
authors: Alongkorn
authors: A
authors: Amnuaykanjanasin
authors: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA.|Syngenta Biotechnology, Research Triangle Park, NC, 27709, USA.
authors: Sonia
authors: S
authors: Herrero
authors: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA.
authors: Elizabeth
authors: E
authors: Thomas
authors: Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA. margaret_daub@ncsu.edu.
authors: Margaret E
authors: ME
authors: Daub
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000935:Antifungal Agents / Q000378:metabolism / Q000494:pharmacology; D025141:Drug Resistance, Fungal / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D018390:Gene Targeting; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009492:Neurospora crassa / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010569:Perylene / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D017319:Photosensitizing Agents / Q000378:metabolism / Q000494:pharmacology; D010802:Phylogeny; D004718:Saccharomycetales / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D026082:Singlet Oxygen / Q000378:metabolism; D014498:Uracil / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D000935:Antifungal Agents; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; D017319:Photosensitizing Agents; C400126:cercosporin transporter protein, Cercospora; D026082:Singlet Oxygen; D014498:Uracil; D010569:Perylene; C026363:cercosporin; D015032:Zinc
keywords: ABC transporter; CRG1; CnATR1; CnCFP; MFS transporter; Perylenequinone; Photosensitizer resistance; Targeted gene disruption