Genetic regulation of the development of mating projections in Candida albicans

Candida albicans MTLa2 regulates the mating response through both the a-factor and α-factor sensing pathways

The diploid fungal pathogen Candida albicans has three configurations at the mating type locus (MTL): heterozygous (a/α) and homozygous (a/a or α/α). C. albicans MTL locus encodes four transcriptional regulators (MTLa1, a2, α1, and α2). The conserved a1/α2 heterodimer controls not only mating competency but also white-opaque heritable phenotypic switching. However, the regulatory roles of MTLa2 and α1 are more complex and remain to be investigated. MTLa/a cells often express a cell type-specific genes and mate as the a-type partner, whereas MTLα/α cells express α-specific genes and mate as the α-type partner. In this study, we report that the MTLa2 regulator controls the formation of mating projections through both the a- and α-pheromone-sensing pathways and thus results in the bi-mater feature of "α cells" of C. albicans. Ectopic expression of MTLa2 in opaque α cells activates the expression of not only MFA1 and STE3 (a-pheromone receptor) but also MFα1 and STE2 (α-pheromone receptor). Inactivation of either the MFa-Ste3 or MFα-Ste2 pheromone-sensing pathway cannot block the MTLa2-induced development of mating projections. However, the case is different in MTLα1-ectopically expressed opaque a cells. Inactivation of the MFα-Ste2 but not the MFa-Ste3 pheromone-sensing pathway blocks MTLα1-induced development of mating projections. Therefore, MTLa2 and MTLα1 exhibit distinct regulatory features that control the mating response in C. albicans. These findings shed new light on the regulatory mechanism of bi-mating behaviors and sexual reproduction in C. albicans.

Clinical characteristics and laboratory indicator analysis of 67 COVID-19 pneumonia patients in Suzhou, China

Background

Sudden exacerbations and respiratory failure are major causes of death in patients with severe coronavirus disease 2019(COVID-19) pneumonia, but indicators for the prediction and treatment of severe patients are still lacking.

Methods

A retrospective analysis of 67 collected cases was conducted and included approximately 67 patients with COVID-19 pneumonia who were admitted to the Suzhou Fifth People’s Hospital from January 1, 2020 to February 8, 2020. The epidemiological, clinical and imaging characteristics as well as laboratory data of the 67 patients were analyzed.

Results

The study found that fibrinogen (FIB) was increased in 45 (65.2%) patients, and when FIB reached a critical value of 4.805 g/L, the sensitivity and specificity、DA, helping to distinguish general and severe cases, were 100 and 14%、92.9%, respectively, which were significantly better than those for lymphocyte count and myoglobin. Chest CT images indicated that the cumulative number of lung lobes with lesions in severe patients was significantly higher than that in general patients (P < 0.05), and the cumulative number of lung lobes with lesions was negatively correlated with lymphocyte count and positively correlated with myoglobin and FIB. Our study also found that there was no obvious effect of hormone therapy in patients with severe COVID-19.

Conclusions

Based on the retrospective analysis, FIB was found to be increased in severe patients and was better than lymphocyte count and myoglobin in distinguishing general and severe patients. The study also suggested that hormone treatment has no significant effect on COVID-19.

N-Acetylglucosamine (GlcNAc) Sensing, Utilization, and Functions in Candida albicans

The sensing and efficient utilization of environmental nutrients are critical for the survival of microorganisms in environments where nutrients are limited, such as within mammalian hosts. Candida albicans is a common member of the human microbiota as well as an opportunistic fungal pathogen. The amide derivative sugar N-acetlyglucosamine (GlcNAc) is an important signaling molecule for C. albicans that could be a major nutrient source for this fungus in host settings. In this article, we review progress made over the past two decades on GlcNAc utilization, sensing, and functions in C. albicans and its related fungal species. GlcNAc sensing and catabolic pathways have been intensively studied in C. albicans. The C. albicans protein Ngt1 represents the first identified GlcNAc-specific transporter in eukaryotic organisms. In C. albicans, GlcNAc not only induces morphological transitions including the yeast to hyphal transition and the white to opaque phenotypic switch, but it also promotes fungal cell death. The Ras-cAMP/PKA signaling pathway plays critical roles in regulating these processes. Given the importance of GlcNAc sensing and utilization in C. albicans, targeting GlcNAc associated pathways and key pathway components could be promising in the development of new antifungal strategies.