The PDR-type ABC transporters AtrA and AtrG are involved in azole drug resistance in <i>Aspergillus oryzae</i>

For strain improvement of <i>Aspergillus oryzae</i>, development of the transformation system is essential, wherein dominant selectable markers, including drug-resistant genes, are available. However, <i>A. oryzae</i> generally has a relatively high resistance to many antifungal drugs effective against yeasts and other filamentous fungi. In the course of the study, while investigating azole drug resistance in <i>A. oryzae</i>, we isolated a spontaneous mutant that exhibited high resistance to azole fungicides and found that pleiotropic drug resistance (PDR)-type ATP-binding cassette (ABC) transporter genes were upregulated in the mutant; their overexpression in the wild-type strain increased azole drug resistance. While deletion of the gene designated <i>atrG</i> resulted in increased azole susceptibility, double deletion of <i>atrG</i> and another gene (<i>atrA</i>) resulted in further azole hypersensitivity. Overall, these results indicate that the ABC transporters AtrA and AtrG are involved in azole drug resistance in <i>A. oryzae</i>. ABC transporters AtrG and AtrA are involved in the azole drug resistance possibly by their drug efflux activities in <i>A. oryzae</i>.针对米曲霉（Aspergillus oryzae）的菌株改良工作，构建遗传转化体系是必不可少的关键环节，当前已有包括耐药基因在内的显性选择标记可用于该体系的开发。然而，米曲霉通常对多种可有效抑制酵母菌及其他丝状真菌的抗真菌药物表现出较高的耐药性。本研究在探究米曲霉的唑类药物耐药机制时，分离得到一株对唑类杀菌剂具有高耐药性的自发突变株，并发现在该突变株中，多药耐药（pleiotropic drug resistance, PDR）型ATP结合盒（ATP-binding cassette, ABC）转运蛋白基因呈现上调表达；将这些基因在野生型菌株中过表达后，可显著提升其对唑类药物的耐药性。单独敲除命名为atrG的基因会使菌株对唑类药物的敏感性升高，而同时敲除atrG与另一基因atrA后，菌株对唑类药物的超敏感性进一步增强。综上，上述结果表明，ABC转运蛋白AtrA与AtrG参与了米曲霉的唑类药物耐药过程；二者可能通过药物外排活性介导米曲霉对唑类药物的耐药性。