A TRP5/5-fluoroanthranilic acid counter-selection system for gene disruption in Candida guilliermondii.

Candida guilliermondii is an interesting biotechnological model for the industrial production of value-added metabolites and also remains an opportunistic emerging fungal agent of candidiasis often associated with oncology patients. The aim of the present study was to establish a convenient transformation system for C. guilliermondii by developing both an ATCC 6260-derived recipient strain and a recyclable selection marker. We first disrupted the TRP5 gene in the wild-type strain and demonstrated that trp5 mutants were tryptophan auxotroph as well as being resistant to the antimetabolite 5-fluoroanthranilic acid (FAA). Following an FAA selection of spontaneous mutants derived from the ATCC 6260 strain and complementation analysis, we demonstrated that trp5 genotypes could be directly recovered on FAA-containing medium. The TRP5 wild-type allele, flanked by two short repeated sequences of its 3'UTR, was then used to disrupt the FCY1 gene in C. guilliermondii trp5 recipient strains. The resulting fcy1 mutants displayed strong flucytosine resistance and a counter-selection on FAA allowed us to pop-out the TRP5 allele from the FCY1 locus. To illustrate the capacity of this blaster system to achieve a second round of gene disruption, we knocked out both the LEU2 and the HOG1 genes in the trp5, fcy1 background. Although all previously described yeast "TRP blaster" disruption systems used TRP1 as counter-selectable marker, this study demonstrated the potential of the TRP5 gene in such strategies. This newly created "TRP5 blaster" disruption system thus represents a powerful genetic tool to study the function of a large pallet of genes in C. guilliermondii.

Fluorescent protein fusions in Candida guilliermondii.

Candida guilliermondii is an emerging fungal agent of candidiasis often associated with oncology patients. This yeast also remains a promising biotechnological model for the industrial production of value-added metabolites. In the present study, we developed a recipient strain as well as a set of plasmids for construction of fluorescent protein (FP) fusions in this species. We demonstrated that C. guilliermondii phosphoglycerate kinase transcription-regulating sequences allow a constitutive expression of codon-optimized green, cyan, yellow and mCherry FP genes in C. guilliermondii cells and the fluorescence signal could be directly observed at the colony and blastospore level by epifluorescence microcopy. To illustrate differential targeting of the FPs into specified cellular compartments, we studied and validated the expected subcellular localization of various C. guilliermondii predicted proteins fused to FPs. Furthermore, co-expression experiments of various couples of FP-tagged C. guilliermondii predicted proteins in the same cell showed that the fluorescence of each FP could be detected independently, providing firm evidences that YFP/CFP and GFP/mCherry pairs can be used for dual labeling in C. guilliermondii cells. This technical advance will facilitate future studies of protein co-expression and co-localization in C. guilliermondii and will give precious help for elucidating new molecular events supporting pathogenicity, antifungal resistance and for exploring the potential of yeast metabolic engineering.

Drug-resistant cassettes for the efficient transformation of Candida guilliermondii wild-type strains.

Candida guilliermondii is an opportunistic emerging fungal agent of candidiasis often associated with oncology patients. This yeast also remains an interesting biotechnological model for the industrial production of value-added metabolites. The recent whole-genome sequencing of the C. guilliermondii ATCC 6260 reference strain provides an interesting resource for elucidating new molecular events supporting pathogenicity, antifungal resistance and for exploring the potential of yeast metabolic engineering. In the present study, we designed an efficient transformation system for C. guilliermondii wild-type strains using both nourseothricin- and hygromycin B-resistant markers. To demonstrate the potential of these drug-resistant cassettes, we carried out the disruption and the complementation of the C. guilliermondii FCY1 gene (which encodes cytosine deaminase) known to be associated with flucytosine sensitivity in yeast. These two new dominant selectable markers represent powerful tools to study the function of a large pallet of genes in this yeast of clinical and biotechnological interest.

Development of a URA5 integrative cassette for gene disruption in the Candida guilliermondii ATCC 6260 strain.

We designed an efficient transformation system for Candida guilliermondii based on a ura5 ATCC 6260 derived recipient strain and a URA5 recyclable selection marker. This "URA5 blaster" disruption system represents a powerful tool to study the function of a large pallet of genes in this yeast of clinical and biotechnological interest.

The in vitro migration capacity of human bone marrow mesenchymal stem cells: comparison of chemokine and growth factor chemotactic activities.

Adult bone marrow (BM)-derived stem cells, including hematopoietic stem cells (HSCs) and MSCs, represent an important source of cells for the repair of a number of damaged tissues. In contrast to HSCs, the soluble factors able to induce MSC migration have not been extensively studied. In the present work, we compared the in vitro migration capacity of human BM-derived MSCs, preincubated or not with the inflammatory cytokines interleukin 1beta (IL1beta) and tumor necrosis factor alpha (TNFalpha), in response to 16 growth factors (GFs) and chemokines. We show that BM MSCs migrate in response to many chemotactic factors. The GFs platelet-derived growth factor-AB (PDGF-AB) and insulin-like growth factor 1 (IGF-1) are the most potent, whereas the chemokines RANTES, macrophage-derived chemokine (MDC), and stromal-derived factor-1 (SDF-1) have limited effect. Remarkably, preincubation with TNFalpha leads to increased MSC migration toward chemokines, whereas migration toward most GFs is unchanged. Consistent with these results, BM MSCs express the tyrosine kinase receptors PDGF-receptor (R) alpha, PDGF-Rbeta, and IGF-R, as well as the RANTES and MDC receptors CCR2, CCR3, and CCR4 and the SDF-1 receptor CXCR4. TNFalpha increases CCR2, CCR3, and CCR4 expression (as opposed to that of CXCR4), together with RANTES membrane binding. These data indicate that the migration capacity of BM MSCs is under the control of a large range of receptor tyrosine kinase GFs and CC and CXC chemokines. Most chemokines are more effective on TNFalpha-primed cells. Our results suggest that the mobilization of MSCs and their subsequent homing to injured tissues may depend on the systemic and local inflammatory state. Disclosure of potential conflicts of interest is found at the end of this article.