Transcriptomics analysis of propiconazole-treated Cochliobolus sativus reveals new putative azole targets in the plant pathogen
Cochliobolus sativus (anamorph: Bipolaris sorokiniana) is a filamentous fungus from the class Dothideomycetes. It is a pathogen of cereals including wheat and barley, and causes foliar spot blotch, root rot, black point on grains, head blight, leaf blight, and seedling blight diseases. Annual yields of these economically important cereals are severely reduced due to this pathogen attack. Evolution of fungicide resistant pathogen strains, availability of a limited number of potent antifungal compounds, and their efficacy are the acute issues in field management of phytopathogenic fungi. Propiconazole is a widely used azole fungicide to control the disease in fields. The known targets of azoles are the demethylase enzymes involved in ergosterol biosynthesis. Nonetheless, azoles have multiple modes of action, some of which have not been explored yet. Identifying the off-target effects of fungicides by dissecting gene expression profiles in response to them can provide insights into their modes of action and possible mechanisms of fungicide resistance. Moreover it can also reveal additional targets for development of new fungicides. Hence, we analyzed the global gene expression profile of C. sativus on exposure to sub-lethal doses of propiconazole in a time series. The gene expression patterns were confirmed using quantitative reverse transcriptase PCR (qRT-PCR). This study revealed overexpression of target genes from the sterol biosynthesis pathway supporting the reported mode of resistance against azoles. In addition, some new potential targets have also been identified, which could be explored to develop new fungicides and plant protection strategies.
KeywordsBipolaris sorokiniana Cochliobolus sativus Fungicide resistance Propiconazole RNA-seq Transcriptomics analysis
ATP binding cassette
Counts per million
Differentially expressed genes
Effective concentration to give half maximal response
Fragments per kilobase million
Hours post treatment
Kyoto Encyclopedia of Genes and Genomes
Log2 fold change
National Center for Biotechnology Information
Potato dextrose agar
Quantitative reverse transcriptase polymerase chain reaction
DS acknowledges the Junior and Senior Research fellowships from the University Grants Commission (UGC), India. The authors thank Dr. Rajeev Kumar, Dept. of Agricultural Biotechnology & Molecular Biology, Dr. Rajendra Prasad Central Agricultural University, Pusa (India) for providing the D2 isolate of C. sativus and Dr. I.K. Kalappanwar, Dept. of Genetics and Plant Breeding, University of Agricultural Sciences, Dharwad (India) for help in microscopic identification of the pathogen. The Centre for Cellular and Molecular Platforms (C-CAMP), Bangalore (India) is acknowledged for RNA sequencing.
NK received financial support in the form of Council of Scientific and Industrial Research (CSIR), India (BSC 0117) and RP received financial support from Department of Biotechnology (DBT), India (GAP 304126).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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