The Yak1p kinase controls expression of adhesins and biofilm formation in Candida glabrata in a Sir4p‐dependent pathway

Abstract

SummaryBiofilm is the predominant type of microbial development in natural environments, and potentially represents a major form of resistance or source of recurrence during host infection. Although a large number of studies have focussed on the genetics of bacterial biofilm formation, very little is known about the genes involved in this type of growth in fungi. A genetic screen for Candida glabrata Biofilm mutants was performed using a 96-well plate model of biofilm formation. Study of the isolated mutant strains allowed the identification of four genes involved in biofilm formation ( RIF1 , SIR4 , EPA6 and YAK1 ). Epa6p is a newly identified adhesin required for biofilm formation in this pathogenic yeast. EPA6 and its close paralogue EPA7 are located in subtelomeric regions and their transcription is regulated by Sir4p and Rif1p, two proteins involved in subtelomeric silencing. Biofilm growth conditions induce the transcription of EPA6 and EPA7 : this is dependent on the presence of an intact subtelomeric silencing machinery and is independent of the Mpk1p signalling pathway. Finally, the kinase Yak1p is required for expression of both adhesin genes and acts through a subtelomeric silencing machinery-dependent pathway.

Detailed comparison of Candida albicans and Candida glabrata biofilms under different conditions and their susceptibility to caspofungin and anidulafungin

“…It was demonstrated previously that C. glabrata EPA6 is transcribed at the highest level during the stationary-growth phase, in contrast to other EPA genes, and that cells in the stationary phase adhered better than metabolically active cells (Iraqui et al, 2005). In all of our assays, C. glabrata cultures were grown up to the stationary phase to ensure that the medium contained totally adherent cell populations.…”

“…For instance, C. albicans adhesins Als1, Als3 and Eap1 are highly expressed in biofilms in vitro (Li et al, 2007;Nailis et al, 2010) and in vivo (Nett et al, 2009;Ř ičicová et al, 2010). In C. glabrata, Epa6 has been shown to be involved in mature biofilm development (Iraqui et al, 2005).…”

“…We therefore analysed the changes in expression of genes participating significantly in adhesion and biofilm formation, such as C. glabrata EPA6 (Iraqui et al, 2005) and C. albicans ALS1, ALS3 and EAP1 (Nailis et al, 2010;Nobile et al, 2006). The results are displayed in Figs 3 and 4(a, b, c), respectively.…”

Identification of Components of the SUMOylation Machinery in Candida glabrata

“…Notably, Epa1 and Epa6 belong to a family of at least 23 cell wall adhesins that mediate adherence of C. glabrata cells to host epithelial cells (39 -41). Epa6 has also been shown to be pivotal to biofilm formation in vitro (42). To examine the effect of EPA6 transcript levels on biofilm formation, we measured the ability of WT, Cgulp2⌬, and Cgulp2⌬-complemented strains to make biofilm on polystyrene-coated plates.…”

“…SUMOylation has previously been implicated in the cellular response to diverse stresses (42,43). We therefore checked alterations in the SUMO proteome of C. glabrata cells upon a 4-h exposure to DNA damage (0.075% MMS), ethanol (10%), oxidative (150 mM H 2 O 2 ) stresses, and antifungal (fluconazole 64 -100 g/ml) stress.…”