ABCG2 and drug resistance: Those involved in pleiotropic drug resistance (PDR) have been studied in yeast, which is known to express various ABC transporters (Matsufuji et al., 2010; Shahi et al., 2010; Tsujimoto et al., 2013, 2015; Gupta et al., 2014; Demir and Koc, 2015).