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Published on: December 28, 2017
Genetic modification of Candida maltosa, a non-pathogenic CTG species, reveals EFG1 function
Marco Chávez-Tinoco1, Luis F García-Ortega1, Eugenio Mancera1
1Departamento de Ingeniería Genética, Unidad Irapuato, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Mexico.
Abstract:
Candida maltosa is closely related to important pathogenic Candida species, especially C. tropicalis and C. albicans, but it has been rarely isolated from humans. For this reason, through comparative studies, it could be a powerful model to understand the genetic underpinnings of the pathogenicity of Candida species. Here, we generated a cohesive assembly of the C. maltosa genome and developed genetic engineering tools that will facilitate studying this species at a molecular level. We used a combination of short and long-read sequencing to build a polished genomic draft composed of 14 Mbp, 45 contigs and close to 5700 genes. This assembly represents a substantial improvement from the currently available sequences that are composed of thousands of contigs. Genomic comparison with C. albicans and C. tropicalis revealed a substantial reduction in the total number of genes in C. maltosa. However, gene loss seems not to be associated to the avirulence of this species given that most genes that have been previously associated with pathogenicity were also present in C. maltosa. To be able to edit the genome of C. maltosa we generated a set of triple auxotrophic strains so that gene deletions can be performed similarly to what has been routinely done in pathogenic Candida species. As a proof of concept, we generated gene knockouts of EFG1, a gene that encodes a transcription factor that is essential for filamentation and biofilm formation in C. albicans and C. tropicalis. Characterization of these mutants showed that Efg1 also plays a role in biofilm formation and filamentous growth in C. maltosa, but it seems to be a repressor of filamentation in this species. The genome assembly and auxotrophic mutants developed here are a key step forward to start using C. maltosa for comparative and evolutionary studies at a molecular level.
Insights
Candida maltosa, a non-pathogenic yeast, offers a model for studying Candida pathogenicity. Researchers developed a new genome assembly and genetic tools, enabling molecular studies and comparative analysis with pathogenic species.
Area of Science:
- Microbiology
- Genomics
- Molecular Biology
Background:
- Candida maltosa is closely related to pathogenic Candida species like C. albicans and C. tropicalis.
- Despite its genetic proximity, C. maltosa is rarely isolated from humans, making it a potential model organism for comparative pathogenicity studies.
- Existing genomic data for C. maltosa is fragmented, hindering detailed molecular analysis.
Purpose of the Study:
- To generate a high-quality, cohesive genome assembly for Candida maltosa.
- To develop genetic engineering tools for C. maltosa, enabling molecular-level investigations.
- To facilitate comparative genomic and evolutionary studies of Candida pathogenicity.
Main Methods:
- Utilized a combination of short-read and long-read sequencing technologies for genome assembly.
- Performed comparative genomics between C. maltosa, C. albicans, and C. tropicalis.
- Generated triple auxotrophic strains of C. maltosa for genetic manipulation.
- Created gene knockouts, specifically targeting the EFG1 gene, to study its function.
Main Results:
- A polished draft genome assembly of 14 Mbp with 45 contigs and approximately 5700 genes was generated, significantly improving upon previous sequences.
- Genomic comparison revealed fewer genes in C. maltosa compared to C. albicans and C. tropicalis, but key pathogenicity-associated genes were retained.
- Auxotrophic mutants were successfully created, and EFG1 gene knockouts demonstrated its role in biofilm formation and filamentation repression in C. maltosa.
Conclusions:
- The new genome assembly and genetic tools provide a robust foundation for molecular studies of C. maltosa.
- C. maltosa can serve as a valuable model organism for understanding the genetic basis of pathogenicity in Candida species.
- Comparative genomic and functional analyses using C. maltosa can elucidate evolutionary pathways and virulence mechanisms in related pathogenic yeasts.
