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Deletion of Candida albicans SPT6 is not lethal but results in defective hyphal growth
Nada Al-Rawi1, Sonia S Laforce-Nesbitt, Joseph M Bliss
1Department of Pediatrics, Women & Infants Hospital of Rhode Island, Warren Alpert Medical School of Brown University, Providence, RI, United States.
Abstract:
As a means to study surface proteins involved in the yeast to hypha transition, human monoclonal antibody fragments (single-chain variable fragments, scFv) have been generated that bind to antigens expressed on the surface of Candida albicans yeast and/or hyphae. A cDNA expression library was constructed from hyphae, and screened for immunoreactivity with scFv5 as a means to identify its cognate antigen. A reactive clone contained the 3' end of the C. albicans gene, orf 19.7136, designated SPT6 based on homology to Saccharomyces cerevisiae, where its product functions as a transcription elongation factor. A mutant containing a homozygous deletion of SPT6 was isolated, demonstrating that unlike S. cerevisiae, deletion of this gene in C. albicans is not lethal. Growth of this strain was severely impaired, however, as was its capacity to undergo filamentous growth. Reactivity with scFv5 was not detected in the mutant strain, although its impaired growth complicates the interpretation of this finding. To assess C. albicansSPT6 function, expression of the C. albicans gene was induced in a defined S. cerevisiaespt6 mutant. Partial complementation was seen, confirming that the C. albicans and S. cerevisiae genes are functionally related in these species.
Insights
Candida albicans SPT6 gene deletion is not lethal but severely impairs growth and filamentous transition. The SPT6 gene is functionally related between C. albicans and Saccharomyces cerevisiae.
Area of Science:
- Molecular Biology
- Mycology
- Genetics
Background:
- Understanding the yeast-to-hypha transition in Candida albicans is crucial for developing antifungal strategies.
- Surface proteins play a key role in this morphological switch.
- Single-chain variable fragments (scFv) are valuable tools for probing surface antigens.
Purpose of the Study:
- To identify surface proteins involved in the Candida albicans yeast-to-hypha transition.
- To characterize the function of the C. albicans SPT6 gene in fungal morphology and growth.
Main Methods:
- Generation of human monoclonal antibody fragments (scFv) against C. albicans surface antigens.
- Construction and screening of a cDNA expression library to identify scFv-binding antigens.
- Gene deletion and complementation studies in C. albicans and Saccharomyces cerevisiae.
Main Results:
- Identified a C. albicans gene, SPT6, homologous to a Saccharomyces cerevisiae transcription elongation factor.
- Homozygous deletion of C. albicans SPT6 was not lethal but resulted in severely impaired growth and filamentous capacity.
- Partial complementation of an S. cerevisiae spt6 mutant by C. albicans SPT6 suggests functional conservation.
Conclusions:
- The C. albicans SPT6 gene is essential for robust growth and the yeast-to-hypha transition.
- SPT6 function is conserved between C. albicans and S. cerevisiae, highlighting its importance in fungal biology.
- Targeting SPT6 could be a potential strategy for controlling C. albicans morphology and virulence.
