Telomeric ORFs (TLOs) in Candida spp. Encode mediator subunits that regulate distinct virulence traits

Area of Science:

• Molecular Biology
• Mycology
• Genetics

Background:

• The TLO gene family encodes subunits of the Mediator complex, homologous to Med2.
• Candida albicans possesses 15 TLO gene copies, while the less virulent C. dubliniensis has two: CdTLO1 and CdTLO2.
• TLO genes are telomere-associated open reading frames (ORFs) in fungal pathogens.

Purpose of the Study:

• To investigate the role of TLO genes in regulating virulence in Candida dubliniensis.
• To determine if TLO paralogs (TLO1 and TLO2) have evolved distinct functional roles.
• To understand the differential regulation of virulence properties by TLO/Med2 paralogs.

Main Methods:

• Construction and analysis of a C. dubliniensis tlo1Δ/tlo2Δ mutant.
• Transcript profiling to analyze gene expression changes in the mutant.
• Chromatin immunoprecipitation (ChIP) studies to identify Tlo1 binding targets.
• Complementation studies using TLO1 and TLO2 to restore wild-type functions.

Main Results:

• The tlo1Δ/tlo2Δ mutant exhibited defects in hyphal formation, increased doubling times, heightened oxidative stress susceptibility, and enhanced biofilm formation.
• Transcript profiling revealed altered expression of starvation and hypha-related genes in the mutant.
• TLO1 and TLO2 displayed distinct complementation capabilities: TLO1 restored filamentous growth and galactose utilization, while TLO2 suppressed biofilm formation and starvation gene transcription.

Conclusions:

• TLO/Med2 paralogs regulate distinct virulence properties in Candida species.
• The expansion of TLO gene family in C. albicans may contribute to its increased adaptability and virulence.
• CdTLO1 and CdTLO2 have evolved specialized functions in regulating fungal growth, stress response, and pathogenesis.