Differential Roles of a Family of Flavodoxin-Like Proteins That Promote Resistance to Quinone-Mediated Oxidative Stress in Candida albicans

Rhizopus stolonifer Exhibits Necrotrophic Behavior when Causing Soft Rot in Ripe Fruit

Rhizopus stolonifer is known for causing soft rot in fruits and vegetables during postharvest. Although it has traditionally been considered a saprophyte, it appears to behave more like a necrotrophic pathogen. In this study, we propose that R. stolonifer invades host tissues by actively killing host cells and overcoming the host defense mechanisms, as opposed to growing saprophytically on decaying plant matter. We tested this hypothesis by characterizing R. stolonifer infection strategies when infecting four fruit hosts (tomato, grape, strawberry, and plum). We started by generating a high-quality genome assembly for R. stolonifer using PacBio sequencing. This led to a genome size of 45.02 Mb, an N50 of 2.87 Mb, and 12,644 predicted loci with protein-coding genes. Next, we performed a transcriptomic analysis to identify genes that R. stolonifer preferentially uses when growing in fruit versus culture media. We categorized these infection-related genes into clusters according to their expression patterns during the interaction with the host. Based on the expression data, we determined that R. stolonifer has a core infection toolbox consisting of strategies typical of necrotrophs, which includes a set of 33 oxidoreductases, 7 proteases, and 4 cell wall-degrading enzymes to facilitate tissue breakdown and maceration across various hosts. This study provides new genomic resources for R. stolonifer and advances the knowledge of Rhizopus-fruit interactions, which can assist in formulating effective and sustainable integrated pest management approaches for soft rot prevention. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Unveiling the roles of CaSDH8 in Candida albicans: Implications for virulence and azole resistance

Candida albicans is the most common pathogen in systemic fungal diseases, exhibits a complex pathogenic mechanism, and is increasingly becoming drug tolerant. Therefore, it is particularly important to study the genes associated with virulence and resistance of C. albicans. Here, we identified a gene (orf19.1588) that encodes a conserved mitochondrial protein known as CaSDH8, upon deletion of CaSdh8, the deleted strain (Casdh8Δ/Δ) experienced impaired growth, hyphal development, and virulence. Casdh8Δ/Δ displayed a reduced capacity to utilize alternative carbon sources, along with detrimental alterations in reactive oxygen species (ROS), mitochondrial membrane potential (MMP) depolarization, and adenosine triphosphate (ATP) levels. Interestingly, Casdh8Δ/Δ demonstrated resistance to azole drugs, and under the influence of fluconazole, the cell membrane permeability and mitochondrial function of Casdh8Δ/Δ were less compromised than those of the wild type, indicating a reduction in the detrimental effects of fluconazole on Casdh8Δ/Δ. These findings highlight the significance of CaSDH8 as a crucial gene for the maintenance of cellular homoeostasis. Our study is the first to document the effects of the CaSDH8 gene on the virulence and azole resistance of C. albicans at both the molecular and animal levels, providing new clues and directions for the antifungal infection and the discovery of antifungal drug targets.

Theoretical-Cheminformatic Study of Four Indolylphytoquinones, Prospective Anticancer Candidates

Background/Objectives: Breast cancer is a disease with a high mortality rate worldwide; consequently, urgent achievements are required to design new greener drugs, leaving natural products and their derivatives as good options. A constant antineoplastic effect has been observed when the phytoproduct contains an indole fragment. Methods: Therefore, the objective of this work was to carry out a thoughtful computational study to perform an appropriate evaluation of four novel molecules of the class of the 3-indolylquinones as phytodrug candidates for antineoplastic activity: thymoquinone (TQ), 2,6-dimethoxy-1,4-benzoquinone (DMQ), 2,3-dimethoxy-5-methyl-1,4-benzoquinone (DMMQ), and 2,5-dihydroxy-1,4-benzoquinone (DHQ). It is important to highlight that the obtained computational results of the target compounds were compared-correlated with the theoretical and experimental literature data previously reported of several indolylquinones: indolylperezone, indolylisoperezone, indolylmenadione, and indolylplumbagin (IE-IH, respectively). Results: The results revealed that the studied structures possibly presented antineoplastic activity, in addition to the fact that the reactivity parameters showed that two of the evaluated compounds have the option to present IC50 values lower than or similar to 25 mg/mL, activity like that of indolylisoperezone; moreover, they show molecular coupling to PARP-1. Finally, the prediction of the calculated physicochemical parameters coincides with the Lipinski and Veber rules, indicating that the adsorption, metabolism, and toxicity parameters are acceptable for the studied compounds, obtaining high drug score values. Conclusions: Finally, a comparison between the proposed molecules and others previously synthesized was appropriately performed, establishing that the synthesis of the studied compounds and the determination of their pharmacological properties in an experimental manner are of interest.

Ferroptosis-protective membrane domains in quiescence

Quiescence is a common cellular state, required for stem cell maintenance and microorganismal survival under stress conditions or starvation. However, the mechanisms promoting quiescence maintenance remain poorly known. Plasma membrane components segregate into distinct microdomains, yet the role of this compartmentalization in quiescence remains unexplored. Here, we show that flavodoxin-like proteins (FLPs), ubiquinone reductases of the yeast eisosome membrane compartment, protect quiescent cells from lipid peroxidation and ferroptosis. Eisosomes and FLPs expand specifically in respiratory-active quiescent cells, and mutants lacking either show accelerated aging and defective quiescence maintenance and accumulate peroxidized phospholipids with monounsaturated or polyunsaturated fatty acids (PUFAs). FLPs are essential for the extramitochondrial regeneration of the lipophilic antioxidant ubiquinol. FLPs, alongside the Gpx1/2/3 glutathione peroxidases, prevent iron-driven, PUFA-dependent ferroptotic cell death. Our work describes ferroptosis-protective mechanisms in yeast and introduces plasma membrane compartmentalization as an important factor in the long-term survival of quiescent cells.

The Candida albicans ζ-crystallin homolog Zta1 promotes resistance to oxidative stress

IMPORTANCE

Candida albicans is an important human pathogen that can cause lethal systemic infections. The ability of C. albicans to colonize and establish infections is closely tied to its highly adaptable nature and capacity to resist various types of stress, including oxidative stress. Previous studies showed that four C. albicans proteins belonging to the flavodoxin-like protein family of quinone reductases are needed for resistance to quinones and virulence. Therefore, in this study, we examined the role of a distinct type of quinone reductase, Zta1, and found that it acts in conjunction with the flavodoxin-like proteins to protect against oxidative stress.

The Candida albicans ζ-crystallin homolog Zta1 promotes resistance to oxidative stress

The fungal pathogen Candida albicans is capable of causing lethal infections in humans. Its pathogenic potential is due in part to the ability to resist various stress conditions in the host, including oxidative stress. Recent studies showed that a family of four flavodoxin-like proteins (Pst1, Pst2, Pst3, Ycp4) that function as quinone reductases promotes resistance to oxidation and is needed for virulence. Therefore, in this study Zta1 was examined because it belongs to a structurally distinct family of quinone reductases that are highly conserved in eukaryotes and have been called the ζ-crystallins. The levels of Zta1 in C. albicans rapidly increased after exposure to oxidants, consistent with a role in resisting oxidative stress. Accumulation of reactive oxygen species was significantly higher in cells lacking ZTA1 upon exposure to quinones and other oxidants. Furthermore, deletion of ZTA1 in a mutant lacking the four flavodoxin-like proteins, resulted in further increased susceptibility to quinones, indicating that these distinct quinone reductases work in combination. These results demonstrate that Zta1 contributes to C. albicans survival after exposure to oxidative conditions, which increases the understanding of how C. albicans resists stressful conditions in the host.

iTRAQ proteomic analysis of the inhibitory effect of 1,6-O,O-diacetylbritannilactone on the plant pathogenic oomycete Phytophthora capsici

Phytophthora capsici is a highly destructive oomycete of vegetables; its management is challenging due to its broad host range, rapid dispersion, resilient spores and severe fungicide resistance. Identifying an effective alternative fungicide is important for the control of P. capsici. 1,6-O,O-diacetylbritannilactone (ABLOO), one of the secondary metabolites of Inula Britannica, showed a favorable inhibitory activity against P. capsici at different developmental stages, with a sensitivity order as follows: sporangia formation (30.45 mg/L) > zoospore discharge (77.69 mg/L) > mycelial growth (93.18 mg/L) > cystospore germination (591.48 mg/L). To investigate the mode of action of ABLOO in P. capsici, iTRAQ-based quantitative proteomic analysis was performed by comparing the expression levels of proteins in the control and ABLOO-treated (400 mg/L, inhibition rate of 80%) mycelial groups. A total of 65 downregulated and 75 upregulated proteins were identified in the proteomic analysis. Functional enrichment analyses showed that proteins with transmembrane transport activity were significantly inhibited, while proteins involved in energy production were significantly increased, including proteins involved in ubiquinone and other terpenoid-quinone biosynthesis, oxidative phosphorylation, and glycolysis/gluconeogenesis. The morphological results indicated that ABLOO treatment could decrease the thickness of the cell walls of P. capsici mycelia. Correspondingly, biochemical results showed that ABLOO treatment reduced the β-1,3-glucan contents (the key component of the cell wall of P. capsici) and increased the cell membrane permeability of P. capsici. ABLOO may exhibit antioomycete activity by destroying the cell membrane of P. capsici. This study provides new evidence regarding the inhibitory mechanisms of ABLOO against P. capsici.