Deletion of the DNA Ligase IV Gene in Candida glabrata Significantly Increases Gene-Targeting Efficiency

Candida glabrata is reported as the second most prevalent human opportunistic fungal pathogen in the United States. Over the last decades, its incidence increased, whereas that ofCandida albicans decreased slightly. One of the main reasons for this shift is attributed to the inherent tolerance ofC. glabrata toward the commonly used azole antifungal drugs. Despite a close phylogenetic distance toSaccharomyces cerevisiae , homologous recombination works with poor efficiency inC. glabrata compared to baker's yeast, in fact limiting targeted genetic alterations of the pathogen's genome. It has been shown that nonhomologous DNA end joining is dominant over specific gene targeting inC. glabrata . To improve the homologous recombination efficiency, we have generated a strain in which theLIG4 gene has been deleted, which resulted in a significant increase in correct gene targeting. The very specific function of Lig4 in mediating nonhomologous end joining is the reason for the absence of clear side effects, some of which affect theku80 mutant, another mutant with reduced nonhomologous end joining. We also generated aLIG4 reintegration cassette. Our results show that thelig4 mutant strain may be a valuable tool for theC. glabrata research community.