The SAT1 flipper, an optimized tool for gene disruption in Candida albicans

被引:617
作者
Reuss, O
Vik, Å
Kolter, R
Morschhäuser, J
机构
[1] Univ Wurzburg, Inst Mol Infek Biol, D-97070 Wurzburg, Germany
[2] Harvard Univ, Sch Med, Dept Microbiol & Mol Genet, Boston, MA 02115 USA
关键词
dominant selection marker; homozygous mutants; marker recycling; nourseothricin resistance; oligopeptide transporter; targeted gene disruption;
D O I
10.1016/j.gene.2004.06.021
中图分类号
Q3 [遗传学];
学科分类号
071007 ; 090102 ;
摘要
The construction of Candida albicans mutants by targeted gene disruption usually depends on the use of nutritional markers for the selection of prototrophic transformants from auxotrophic host strains, but it is becoming increasingly evident that this strategy may cause difficulties in the interpretation of mutant phenotypes. Here, we describe a new method for inactivating both alleles of a target gene in C. albicans wild-type strains to obtain homozygous null mutants. The SAT1 flipping method relies on the use of a cassette that contains a dominant nourseothricin resistance marker (caSAT1) for the selection of integrative transformants and a C albicans-adapted FLP gene that allows the subsequent excision of the cassette, which is flanked by FLP target sequences, from the genome. Two rounds of integration/excision generate homozygous mutants that differ from the wild-type parent strain only by the absence of the target gene, and reintegration of an intact gene copy for complementation of mutant phenotypes is performed in the same way. Transformants are obtained after only 1 day of growth on a selective medium, and integration into the target locus occurs with high specificity after adding homologous flanking sequences on both sides of the cassette. FLP-mediated excision of the SAT1 flipper cassette is achieved by simply growing the transformants for a few hours in medium without selective pressure, and nourseothricin-sensitive (Nou(S)) derivatives can easily be identified by their slower growth on indicator plates containing a low concentration of nourseothricin. We demonstrate the use of the system by deleting the OPT1 gene, which encodes an oligopeptide transporter, in the C albicans model strain SC5314. The null mutants became resistant to the toxic peptide KLLEth, and reintroduction of an intact OPT1 copy restored susceptibility. The SAT1 flipping method provides a highly efficient method for gene disruption in C. albicans wild-type strains, which eliminates currently encountered problems in the genetic analysis of this important human fungal pathogen. (C) 2004 Elsevier B.V. All rights reserved.
引用
收藏
页码:119 / 127
页数:9
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