Directed Evolution Detects Supernumerary Centric Chromosomes Conferring Resistance to Azoles in Candida auris
Aswathy Narayanan, Praveen Kumar, Anshu Chauhan, Mohit Kumar, Kusum Yadav, Atanu Banerjee, Ravi Datta Sharma, Shivaprakash M. Rudramurthy, Arunaloke Chakrabarti, Kaustuv Sanyal, Rajendra Prasad
Abstract
Fungal pathogens develop drug resistance through multiple pathways by acquiring gene mutations, increasing the copy number of genes, or altering gene expression. In this study, we attempt to understand the mechanisms of drug resistance in the recently emerged superbug, C. auris. One approach to studying this aspect is identifying various mechanisms operating in drug-resistant clinical isolates. An alternative approach is to evolve a drug-susceptible isolate in the presence of an antifungal compound and trace the changes that result in drug resistance. Here, we evolve a drug-susceptible isolate of C. auris in the laboratory in the presence of a widely used antifungal compound, fluconazole. In addition to the already known changes like overexpression of drug efflux pumps, this study identifies a novel mechanism of azole resistance by the emergence of additional chromosomes through segmental duplication of chromosomal regions, including centromeres. The centric supernumerary chromosome helps stable amplification of a set of genes with an extra copy to confer fluconazole resistance.