Furthermore, C. albicans, Smad cancer as well as related species, are able to spontaneously and reversibly make the switch between two or more general phenotypes, reflected by distinct colony morphologies [43]. In order to investigate if CaGUP1

was implicated in C. albicans morphogenesis, young cultures of wt and Cagup1Δ null mutant strains were cultivated on agar plates under several conditions. Colonies from both strains formed in non-hypha-inducing conditions (YPD at 30°C) are similar in shape, without peripheral hyphae and no hyphal cells within the colony (see Additional file 3). Investigation under hypha-induced conditions presented significant differences between the two strains (Figure 3). In opposition to wt, the colonies of Cagup1Δ null mutant strain did not show filaments, either peripheral or inside the colony, suggesting that the mutant lost the BI 2536 ability to form hyphae under the tested conditions. Furthermore, these colonies show a remarkable distinct/aberrant morphology i.e. flower, spaghetti, irregular wrinkled shape when compared to wt. In the same figure it is possible to see that, the GUP1 complemented strain CF-Ca001

displayed a comparable behaviour to wt. The introduction of the empty Clp20 plasmid into Cagup1Δ null mutant or into wt did not cause any amendment on these strains morphology (not shown). Most interesting, when visualized under the microscope, cells within the colonies of the mutant strain were all yeast-type (Figure 3B – panel V and VI), and not a mixture of hyphae and blastospores as described in the literature [4, 44]. The same pattern was observed irrespectively of the medium used. Figure 3 Ca gup1Δ null mutation leads to aberrant colony morphology, precluding filamentous growth. (A) In both YPD and Spider medium, Cagup1Δ null mutant strain colonies are wrinkled (spaghetti/flower shaped) with no peripheral filamentous growth – panels I and III. The contour of these colonies observed with LM,

fully confirms this absence, in clear contrast with wt and CB-839 CF-Ca001 colonies – panels II and IV. (B) Growth on YPD supplemented with DNA ligase 10% FBS at 37°C yields identical results: colony morphology by magnifying lens (I) and by LM (II), colony contour morphology by LM (III), colony internal structure by LM (IV), and individual cells morphology by LM (V, VI). The gup1Δ photos are representative of the results obtained with the several clones (3-5) of Cagup1Δ null mutant strain tested. Time-course of hyphae formation induced by FBS (fetal bovine serum) in liquid medium was also checked. Wt displayed filamentous growth soon after induction (15 min) (Figure 4A) whereas with the Cagup1Δ null mutant strain this switch was not observed before 1.5 h. During the remaining time of the experiment, filamentous cells from the Cagup1Δ null mutant strain were barely detectable when compared to wt.