RNA-sequencing of Cercospora beticola DMI-sensitive and -resistant isolates after treatment with tetraconazole identifies common and contrasting pathway induction.
Cercospora beticola causes Cercospora leaf spot of sugar beet. Cercospora leaf spot management measures often include application of the sterol demethylation inhibitor (DMI) class of fungicides. The reliance on DMIs and the consequent selection pressures imposed by their widespread use has led to the emergence of resistance in C. beticola populations. Insight into the molecular basis of tetraconazole resistance may lead to molecular tools to identify DMI-resistant strains for fungicide resistance management programs. Previous work has shown that expression of the gene encoding the DMI target enzyme (CYP51) is generally higher and inducible in DMI-resistant C. beticola field strains. In this study, we extended the molecular basis of DMI resistance in this pathosystem by profiling the transcriptional response of two C. beticola strains contrasting for resistance to tetraconazole. A majority of the genes in the ergosterol biosynthesis pathway were induced to similar levels in both strains with the exception of CbCyp51, which was induced several-fold higher in the DMI-resistant strain. In contrast, a secondary metabolite gene cluster was induced in the resistance strain, but repressed in the sensitive strain. Genes encoding proteins with various cell membrane fortification processes were induced in the resistance strain. Site-directed and ectopic mutants of candidate DMI-resistance genes all resulted in significantly higher EC50 values than the wild-type strain, suggesting that the cell wall and/or membrane modified as a result of the transformation process increased resistance to tetraconazole. Taken together, this study identifies important cell membrane components and provides insight into the molecular events underlying DMI resistance in C. beticola.
USDA - ARS, Northern Crop Science Laboratory, Fargo, ND, USA; North Dakota State University, Department of Plant Pathology, Fargo, ND, USA. Electronic address: Melvin.Bolton@ars.usda.gov.
Melvin D
MD
Bolton
USDA - ARS, Northern Crop Science Laboratory, Fargo, ND, USA; North Dakota State University, Department of Plant Pathology, Fargo, ND, USA; Wageningen University, Laboratory of Phytopathology, Wageningen, The Netherlands.
Malaika K
MK
Ebert
Wageningen University, Laboratory of Phytopathology, Wageningen, The Netherlands.
Luigi
L
Faino
North Dakota State University, Department of Plant Pathology, Fargo, ND, USA.
Viviana
V
Rivera-Varas
Department of Plant Systems Biology, VIB, Ghent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent Belgium.
Ronnie
R
de Jonge
Department of Plant Systems Biology, VIB, Ghent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent Belgium.
Yves
Y
Van de Peer
Wageningen University, Laboratory of Phytopathology, Wageningen, The Netherlands.
Bart P H J
BP
Thomma
North Dakota State University, Department of Plant Pathology, Fargo, ND, USA.
Gary A
GA
Secor
D058888:14-alpha Demethylase Inhibitors / Q000494:pharmacology; D001203:Ascomycota / Q000187:drug effects / Q000235:genetics*; D001483:Base Sequence; D002722:Chlorobenzenes / Q000494:pharmacology; D025141:Drug Resistance, Fungal / Q000235:genetics*; D004875:Ergosterol / Q000096:biosynthesis / Q000235:genetics*; D005659:Fungicides, Industrial / Q000494:pharmacology; D059014:High-Throughput Nucleotide Sequencing; D009154:Mutation; D058886:Sterol 14-Demethylase / Q000096:biosynthesis / Q000235:genetics*; D014230:Triazoles / Q000494:pharmacology; D005466:Fluorocarbons
D058888:14-alpha Demethylase Inhibitors; D002722:Chlorobenzenes; D004875:Ergosterol; D005659:Fungicides, Industrial; D058886:Sterol 14-Demethylase; D014230:Triazoles; C524826:tetraconazole; D005466:Fluorocarbons
Cell-membrane; EC(50); Ergosterol; RTA1; Sterol demethylation inhibitor; Tetraconazole; Transformation