Role of Calcium/Calcineurin Signalling in Regulating Intracellular Reactive Oxygen Species Homeostasis in Saccharomyces cerevisiae

Shedding Light on Calcium Dynamics in the Budding Yeast: A Review on Calcium Monitoring with Recombinant Aequorin

Recombinant aequorin has been extensively used in mammalian and plant systems as a powerful tool for calcium monitoring. While aequorin has also been widely applied in yeast research, a notable gap exists in the literature regarding comprehensive reviews of these applications. This review aims to address that gap by providing an overview of how aequorin has been used to explore calcium homeostasis, signaling pathways, and responses to stressors, heavy metals, and toxic compounds in Saccharomyces cerevisiae. We also discuss strategies for further developing the aequorin system in yeast, with particular emphasis on its use as a model for human calcium signaling studies, such as the reproduction of the mitochondrial calcium uniporter. By highlighting previous research and pinpointing potential future applications, we discuss the untapped potential of aequorin in yeast for drug screening, environmental toxicity testing, and disease-related studies.

Transcriptome Analysis Provides Insights into the Mechanism of the Transcription Factor AaCrz1 Regulating the Infection Structure Formation of Alternaria alternata Induced by Pear Peel Wax Signal

Alternaria alternata, a causal agent of pear black spot, can recognize and respond to physicochemical signals from fruit surfaces through an intricate signaling network to initiate infection. Crz1 is an important transcription factor downstream of the calcium signaling pathway. In this study, we first investigated the infection structure formation process of the wild type (WT) and ΔAaCrz1 strains induced by the cuticular wax of the "Zaosu" pear by microscopic observation. We found that the infection process was delayed and the rate of appressorium formation and infection hyphae formation was significantly decreased in the ΔAaCrz1 strain. RNA-seq of WT and ΔAaCrz1 strains was analyzed after 6 h of induction with pear wax. A total of 893 up-regulated and 534 down-regulated genes were identified. Among them, genes related to cell wall degrading enzymes, ABC transporters, and ion homeostasis were down-regulated, and the autophagy pathway was induced and activated. In addition, disruption to the intracellular antioxidant system was also found after AaCrz1 knockdown. In summary, this study provides new information on the mechanism of the transcription factor AaCrz1 in the regulation of infection structure formation of A. alternata induced by pear peel wax signal, which can be used to develop new strategies for controlling fungal diseases in the future.

Crucial aspects of metabolism and cell biology relating to industrial production and processing of Saccharomyces biomass

The multitude of applications to which Saccharomyces spp. are put makes these yeasts the most prolific of industrial microorganisms. This review considers biological aspects pertaining to the manufacture of industrial yeast biomass. It is proposed that the production of yeast biomass can be considered in two distinct but interdependent phases. Firstly, there is a cell replication phase that involves reproduction of cells by their transitions through multiple budding and metabolic cycles. Secondly, there needs to be a cell conditioning phase that enables the accrued biomass to withstand the physicochemical challenges associated with downstream processing and storage. The production of yeast biomass is not simply a case of providing sugar, nutrients, and other growth conditions to enable multiple budding cycles to occur. In the latter stages of culturing, it is important that all cells are induced to complete their current budding cycle and subsequently enter into a quiescent state engendering robustness. Both the cell replication and conditioning phases need to be optimized and considered in concert to ensure good biomass production economics, and optimum performance of industrial yeasts in food and fermentation applications. Key features of metabolism and cell biology affecting replication and conditioning of industrial Saccharomyces are presented. Alternatives for growth substrates are discussed, along with the challenges and prospects associated with defining the genetic bases of industrially important phenotypes, and the generation of new yeast strains."I must be cruel only to be kind: Thus bad begins, and worse remains behind." William Shakespeare: Hamlet, Act 3, Scene 4.

Involvement of oxidative species in cyclosporine-mediated cholestasis

Cyclosporine is an established medication for the prevention of transplant rejection. However, adverse consequences such as nephrotoxicity, hepatotoxicity, and cholestasis have been associated with prolonged usage. In cyclosporine-induced obstructive and chronic cholestasis, for example, the overproduction of oxidative stress is significantly increased. Additionally, cyclosporine exerts adverse effects on liver function and redox balance responses in treated rats, as evidenced by its increasing levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin while also decreasing the levels of glutathione and NADPH. Cyclosporine binds to cyclophilin to produce its therapeutic effects, and the resulting complex inhibits calcineurin, causing calcium to accumulate in the mitochondria. Accumulating calcium with concomitant mitochondrial abnormalities induces oxidative stress, perturbation in ATP balance, and failure of calcium pumps. Also, cyclosporine-induced phagocyte oxidative stress generation via the interaction of phagocytes with Toll-like receptor-4 has been studied. The adverse effect of cyclosporine may be amplified by the release of mitochondrial DNA, mediated by oxidative stress-induced mitochondrial damage. Given the uncertainty surrounding the mechanism of cyclosporine-induced oxidative stress in cholestasis, we aim to illuminate the involvement of oxidative stress in cyclosporine-mediated cholestasis and also explore possible strategic interventions that may be applied in the future.

Protection of the DNA from Selected Species of Five Kingdoms in Nature by Ba(II), Sr(II), and Ca(II) Silica-Carbonates: Implications about Biogenicity and Evolving from Prebiotic Chemistry to Biological Chemistry

The origin of life on Earth is associated with the Precambrian era, in which the existence of a large diversity of microbial fossils has been demonstrated. Notwithstanding, despite existing evidence of the emergence of life many unsolved questions remain. The first question could be as follows: Which was the inorganic structure that allowed isolation and conservation of the first biomolecules in the existing reduced conditions of the primigenial era? Minerals have been postulated as the ones in charge of protecting theses biomolecules against the external environment. There are calcium, barium, or strontium silica-carbonates, called biomorphs, which we propose as being one of the first inorganic structures in which biomolecules were protected from the external medium. Biomorphs are structures with different biological morphologies that are not formed by cells, but by nanocrystals; some of their morphologies resemble the microfossils found in Precambrian cherts. Even though biomorphs are unknown structures in the geological registry, their similarity with some biological forms, including some Apex fossils, could suggest them as the first "inorganic scaffold" where the first biomolecules became concentrated, conserved, aligned, and duplicated to give rise to the pioneering cell. However, it has not been documented whether biomorphs could have been the primary structures that conserved biomolecules in the Precambrian era. To attain a better understanding on whether biomorphs could have been the inorganic scaffold that existed in the primigenial Earth, the aim of this contribution is to synthesize calcium, barium, and strontium biomorphs in the presence of genomic DNA from organisms of the five kingdoms in conditions emulating the atmosphere of the Precambrian era and that CO₂ concentration in conditions emulating current atmospheric conditions. Our results showed, for the first time, the formation of the kerogen signal, which is a marker of biogenicity in fossils, in the biomorphs grown in the presence of DNA. We also found the DNA to be internalized into the structure of biomorphs.