The GOA1p of Candida albicans localizes to the mitochondria during oxidant and osmotic stress and is required for a stress response
Thesis (Ph.D.)--Georgetown University, 2009.; Includes bibliographical references.; Text (Electronic thesis) in PDF format. Using a Tn7 transposon library of C. albicans, we have identified a mutant that exhibited sensitivity in drop plate assays to oxidants such as menadione and hydrogen peroxide. To verify the role of the mutated gene in stress adaptation, null mutants were constructed and phenotypically characterized. Because of its apparent functions in growth and oxidant adaptation, we have named the gene GOA1. Goa1p appears to be unique to the CTG subclade of the Saccharomycotina, including C. albicans. Mutants of C. albicans lacking goa1 (strain GOA31) were more sensitive to 6 mM H2O2, 0.125 mM menadione, and 1.5 M NaCl than wild type or a gene reconstituted (GOA32) strain. The sensitivity to oxidants correlated with reduced survival of the GOA31 mutant in human neutrophils (PMNs) and avirulence compared to control strains. Other phenotypes of GOA31 include reduced growth and filamentation in 10% serum, Spider, and SLAD agar media, and an inability to form chlamydospores. Transcription of GOA1 increased during stress with 1 M NaCl. Transcription of GOA1 was also studied in the MAPK mutants hog1, mkc1, cek1, and cek2 as well as in a cap1 mutant. Since Goa1p has an N-terminal mitochondrion localization site, we demonstrated that GFP-tagged Goa1p was translocated to the mitochondria during osmotic and oxidant stress. Further, the inability of GOA31 to grow in media containing lactate, ethanol, or glycerol as the sole carbon source indicates that the mitochondria are defective in the mutant.
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