Anderson James B, Sirjusingh Caroline, Syed Nazia, Lafayette Shantelle
Department of Cell and Systems Biology, University of Toronto, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada.
Antimicrob Agents Chemother. 2009 May;53(5):1931-6. doi: 10.1128/AAC.01315-08. Epub 2009 Mar 9.
Permanent changes in gene expression result from certain forms of antifungal resistance. In this study, we asked whether any changes in gene expression are required for the evolution of a drug-resistant phenotype in populations. We examined the changes in gene expression resulting from the evolution of resistance in experimental populations of the yeast Saccharomyces cerevisiae with two antifungal drugs, fluconazole (FLC) in a previous study and amphotericin B (AmB) in this study, in which five populations were subjected to increasing concentrations of AmB, from 0.25 to 128 microg/ml in twofold increments. Six genes, YGR035C, YOR1, ICT1, GRE2, PDR16, and YPLO88W, were consistently overexpressed with resistance to AmB reported here and with resistance to FLC involving a mechanism of increased efflux reported previously. We then asked if the deletion of these genes impaired the ability of populations to evolve resistance to FLC over 108 generations of asexual reproduction in 32 and 128 microg/ml FLC, the same conditions under which FLC-resistant types evolved originally. For each of three deletion strains, YOR1, ICT1, and PDR16 strains, extinctions occurred in one of two replicate populations growing in 128 microg/ml FLC. Each of these three deletion strains was mixed 1:1 with a marked version of the wild type to measure the relative ability of the deletion strain to adapt over 108 generations. In these assays, only the PDR16 deletion strain consistently became extinct both at 32 and at 128 microg/ml FLC. The deletion of PDR16 reduces the capacity of a population to evolve to resistance to FLC.
基因表达的永久性变化源于某些形式的抗真菌抗性。在本研究中，我们探讨了群体中耐药表型的进化是否需要基因表达发生任何变化。我们研究了酿酒酵母实验群体中抗性进化所导致的基因表达变化，在之前的一项研究中使用了氟康唑（FLC），本研究中使用了两性霉素B（AmB），其中五个群体接受了浓度不断增加的AmB处理，从0.25μg/ml到128μg/ml，以两倍递增。六个基因，YGR035C、YOR1、ICT1、GRE2、PDR16和YPLO88W，在此处报道的对AmB的抗性以及先前报道的涉及外排增加机制的对FLC的抗性中持续过表达。然后我们询问，在32μg/ml和128μg/ml FLC的条件下，经过108代无性繁殖，这些基因的缺失是否会损害群体进化出对FLC抗性的能力，这与最初进化出FLC抗性类型的条件相同。对于三个缺失菌株中的每一个，即YOR1、ICT1和PDR16菌株，在128μg/ml FLC中生长的两个重复群体之一中出现了灭绝。将这三个缺失菌株中的每一个与标记版本的野生型以1:1混合，以测量缺失菌株在108代中适应的相对能力。在这些试验中，只有PDR16缺失菌株在32μg/ml和128μg/ml FLC时都持续灭绝。PDR16的缺失降低了群体进化出对FLC抗性的能力。
