R-SNARE FgSec22 is essential for growth, pathogenicity and DON production of Fusarium graminearum.

SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) facilitate intracellular vesicle trafficking and membrane fusion in eukaryotic cells, and play a vital role in growth, development and pathogenicity of phytopathogens. Fusarium head blight (FHB) caused by F. graminearum is one of the most devastating diseases of wheat and barley worldwide. Sec22 is a member of the SNARE family of proteins and its homologues have been shown to have diverse biological roles in different organisms. However, the functions of this protein in the development and pathogenesis of F. graminearum are currently unknown. In this study, we employed integrated biochemical, microbiological and molecular genetic approaches to investigate the roles of FgSec22 in F. graminearum. Our data reveal that this SNARE protein is localized to endoplasmic reticulum (ER) and is indispensable for normal conidiation, conidial morphology and pathogenesis of this phytopathogenic fungus. Our biochemical assay of deoxynivalenol (DON) reveals the active involvement of this protein in the production of this mycotoxin in F. graminearum. This has further been confirmed by qRT-PCR analyses of trichothecene (TRI) genes' expression where the ΔFgsec22 deletion mutant demonstrated a significant down-regulation of these genes in comparison to the wild-type PH-1. Unlike the wild-type and the complemented strain, the mutant strain presents a remarkable defect in colony formation which reflects the critical role it plays in vegetative growth. Collectively, our data support that the SNARE protein FgSec22 is required for vegetative growth, pathogenesis and DON biosynthesis in F. graminearum.

The 5-oxoprolinase is required for conidiation, sexual reproduction, virulence and deoxynivalenol production of Fusarium graminearum.

In eukaryotic organisms, the 5-oxoprolinase is one of the six key enzymes in the γ-glutamyl cycle that is involved in the biosynthetic pathway of glutathione (GSH, an antioxidative tripeptide counteracting the oxidative stress). To date, little is known about the biological functions of the 5-oxoprolinase in filamentous phytopathogenic fungi. In this study, we investigated the 5-oxoprolinase in Fusarium graminearum for the first time. In F. graminearum, two paralogous genes (FgOXP1 and FgOXP2) were identified to encode the 5-oxoprolinase while only one homologous gene encoding the 5-oxoprolinase could be found in other filamentous phytopathogenic fungi or Saccharomyces cerevisiae. Deletion of FgOXP1 or FgOXP2 in F. graminearum led to significant defects in its virulence on wheat. This is likely caused by an observed decreased deoxynivalenol (DON, a mycotoxin) production in the gene deletion mutant strains as DON is one of the best characterized virulence factors of F. graminearum. The FgOXP2 deletion mutant strains were also defective in conidiation and sexual reproduction while the FgOXP1 deletion mutant strains were normal for those phenotypes. Double deletion of FgOXP1 and FgOXP2 led to more severe defects in conidiation, DON production and virulence on plants, suggesting that both FgOXP1 and FgOXP2 play a role in fungal development and plant colonization. Although transformation of MoOXP1into ΔFgoxp1 was able to complement ΔFgoxp1, transformation of MoOXP1 into ΔFgoxp2 failed to restore its defects in sexual development, DON production and pathogenicity. Taken together, these results suggest that FgOXP1 and FgOXP2 are likely to have been functionally diversified and play significant roles in fungal development and full virulence in F. graminearum.

Prognostic and immunological implications of glutathione metabolism genes in lung adenocarcinoma: A focus on the core gene SMS and its impact on M2 macrophage polarization.

Glutathione metabolism (GM) is a crucial part of various metabolic and pathophysiological processes. However, its role in lung adenocarcinoma (LUAD) has not been comprehensively studied. This study aimed to explore the potential relationship between GM genes, the prognosis, and the immune microenvironment of patients with LUAD. We constructed a risk signature model containing seven GM genes using Lasso combined Cox regression and validated it using six GEO datasets. Our analysis showed that it is an independent prognostic factor. Functional enrichment analysis revealed that the GM genes were significantly enriched in cell proliferation, cell cycle regulation, and metabolic pathways. Clinical and gene expression data of patients with LUAD were obtained from the TCGA database and patients were divided into high- and low-risk groups. The high-risk patient group had a poor prognosis, reduced immune cell infiltration, poor response to immunotherapy, high sensitivity to chemotherapy, and low sensitivity to targeted therapy. Subsequently, single-cell transcriptome analysis using the GSE143423 and GSE127465 datasets revealed that the core SMS gene was highly enriched in M2 Macrophages. Finally, nine GEO datasets and multiple fluorescence staining revealed a correlation between the SMS expression and M2 macrophage polarization. Our prognostic model in which the core SMS gene is closely related to M2 macrophage polarization is expected to become a novel target and strategy for tumor therapy.

Identification of a hemorrhagic determinant in Clostridioides difficile TcdA and Paeniclostridium sordellii TcsH.

Paeniclostridium sordellii hemorrhagic toxin (TcsH) and Clostridioides difficile toxin A (TcdA) are two major members of the large clostridial toxin (LCT) family. These two toxins share ~87% similarity and are known to cause severe hemorrhagic pathology in animals. Yet, the pathogenesis of their hemorrhagic toxicity has been mysterious for decades. Here, we examined the liver injury after systemic exposure to different LCTs and found that only TcsH and TcdA induce overt hepatic hemorrhage. By investigating the chimeric and truncated toxins, we demonstrated that the enzymatic domain of TcsH alone is not sufficient to determine its potent hepatic hemorrhagic toxicity in mice. Likewise, the combined repetitive oligopeptide (CROP) domain of TcsH/TcdA alone also failed to explain their strong hemorrhagic activity in mice. Lastly, we showed that disrupting the first two short repeats of CROPs in TcsH and TcdA impaired hemorrhagic toxicity without causing overt changes in cytotoxicity and lethality. These findings lead to a deeper understanding of toxin-induced hemorrhage and the pathogenesis of LCTs and could be insightful in developing therapeutic avenues against clostridial infections. IMPORTANCE: Paeniclostridium sordellii and Clostridioides difficile infections often cause hemorrhage in the affected tissues and organs, which is mainly attributed to their hemorrhagic toxins, TcsH and TcdA. In this study, we demonstrate that TcsH and TcdA, but not other related toxins. including Clostridioides difficile toxin B and TcsL, induce severe hepatic hemorrhage in mice. We further determine that a small region in TcsH and TcdA is critical for the hemorrhagic toxicity but not cytotoxicity or lethality of these toxins. Based on these results, we propose that the hemorrhagic toxicity of TcsH and TcdA is due to an uncharacterized mechanism, such as the presence of an unknown receptor, and future studies to identify the interactive host factors are warranted.

Paeniclostridium sordellii hemorrhagic toxin targets TMPRSS2 to induce colonic epithelial lesions.

Hemorrhagic toxin (TcsH) is an important exotoxin produced by Paeniclostridium sordellii, but the exact role of TcsH in the pathogenesis remains unclear, partly due to the lack of knowledge of host receptor(s). Here, we carried out two genome-wide CRISPR/Cas9 screens parallelly with TcsH and identified cell surface fucosylation and TMPRSS2 as host factors contributing to the binding and entry of TcsH. Genetic deletion of either fucosylation biosynthesis enzymes or TMPRSS2 in the cells confers resistance to TcsH intoxication. Interestingly, TMPRSS2 and fucosylated glycans can mediate the binding/entry of TcsH independently, thus serving as redundant receptors. Both TMPRSS2 and fucosylation recognize TcsH through its CROPs domain. By using Tmprss2‒/‒ mice, we show that Tmprss2 is important for TcsH-induced systematic toxicity and colonic epithelial lesions. These findings reveal the importance of TMPRSS2 and surface fucosylation in TcsH actions and further provide insights into host recognition mechanisms for large clostridial toxins.