MSS2 maintains mitochondrial function and is required for chitosan resistance, invasive growth, biofilm formation and virulence in Candida albicans
Authors: Cai-Ling Ke
Yu-Ting Liao
Ching-Hsuan Lin
Journal: Virulence (2021)
Discipline: IMMUNOLOGY
Keywords: Candida albicans; MSS2; biofilms; chitosan; mitochondria
Affiliations: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan

Abstract:  Candida albicans is the most prevalent fungal pathogen in humans, particularly in immunocompromised patients. In this study, by screening a C. albicans mutant library, we first identified that the MSS2 gene, an ortholog of Saccharomyces cerevisiae MSS2 required for mitochondrial respiration, mediates chitosan resistance. Upon treatment with 0.2% chitosan, the growth of mss2Œî strains was strikingly impaired, and MSS2 expression was significantly repressed by chitosan. Furthermore, mss2Œî strains exhibited slow growth on medium supplemented with glycerol as the sole carbon source. Similar to the chitosan-treated wild-type strain, the mss2Œî strain exhibited a significantly impaired ATP production ability. These data suggest that an antifungal mechanism of chitosan against C. albicans acts by inhibiting MSS2 gene expression, leading to repression of mitochondrial function. Normal respiratory function is suggested to be required for fungal virulence. Interestingly, the mss2Œî mutant strains exhibited significantly impaired invasive ability in vitro and ex vivo but retained normal hyphal development ability in liquid medium. Furthermore, the MSS2 deletion strains could not form robust biofilms and exhibited significantly reduced virulence. Collectively, these results demonstrated that the antifungal effect of chitosan against C. albicans is mediated via inhibition of mitochondrial biogenesis. These data may provide another strategy for antifungal drug development via inhibition of fungal mitochondria. 

Retracted: No

PubPeer comments:
 In Figure 5d, the merged micrograph in many of the panels do not correspond with the single staining micrographs.  , 
 Thank you for point out this. In fact, these images are correct. I donu2019t know why the image published by the Journal is vague. Below please find the image link. This is what we uploaded to the Journal. The images of the WT and mss2u0394: MSS2#2 are very clear in the uploaded image, so they looks fine. Although fluorescence of the CW image of the hyphal tail of mss2u0394#2 is not clear (maybe due to a little bit out of focus when the filter was changed), it does have fluorescence, which means that the hypha did not penetrate into the cell. Anyway, thank you very much. It is great that I can provide the clear image here for readers. Please let me know if you are unable to access the image. (http: drive.google.com file d 1CWpD3HGHhMiyEOEe0rBjSCE3KcJ8SZzN view?usp=sharing) We also provide a brief protocol for the experiment. Concanavalin A (ConA) and calcofluor white (CW) were used to differentiate hyphae that contacted the epithelial cell surface and hyphae that had actually invaded the epithelial cells. ConA was to stain C. albicans cells localized outside the epithelial cells because it cannot penetrate cell membrane of HeLa cells. The membranes of epithelial cells were subsequently permeabilized with 0.1% Triton X-100 detergent. CW was then used to stain C. albicans cells localized outside of and inside epithelial cells. In general, if the hyphal tip exhibited blue color in the Merge images, it penetrated into the cell. If pink color showed up, it did not penetrate into the cell. ,