Spermidine Is Critical for Growth, Development, Environmental Adaptation, and Virulence in Fusarium graminearum

FgUbiH Is Essential for Vegetative Development, Energy Metabolism, and Antioxidant Activity in Fusarium graminearum

Fusarium head blight in wheat is mainly caused by Fusarium graminearum and results in significant economic losses. Coenzyme Q (CoQ) is ubiquitously produced across organisms and functions as a hydrogen carrier in energy metabolism. While UbiH in Escherichia coli serves as a hydroxylase in CoQ biosynthesis, its role in phytopathogenic fungi is not well understood. This study explored the role of the hydroxylase FgUbiH in F. graminearum. Using a FgUbiH deletion mutant, we observed reduced hyphal growth, conidial production, germination, toxin synthesis, and pathogenicity compared to the wild-type. A transcriptome analysis indicated FgUbiH's involvement in regulating carbohydrate and amino acid metabolism. Deletion of FgUbiH impaired mitochondrial function, reducing adenosine triphosphate synthesis and increasing reactive oxygen species. Additionally, genes related to terpene skeleton synthesis and aldehyde dehydrogenase were downregulated. Our results underscore the importance of FgUbiH in F. graminearum's growth, toxin production, and energy metabolism, aiding in the development of strategies for disease management.

Polyamines in Plant-Pathogen Interactions: Roles in Defense Mechanisms and Pathogenicity with Applications in Fungicide Development

Polyamines (PAs), which are aliphatic polycationic compounds with a low molecular weight, are found in all living organisms and play essential roles in plant-pathogen interactions. Putrescine, spermidine, and spermine, the most common PAs in nature, respond to and function differently in plants and pathogens during their interactions. While plants use certain PAs to enhance their immunity, pathogens exploit PAs to facilitate successful invasion. In this review, we compile recent studies on the roles of PAs in plant-pathogen interactions, providing a comprehensive overview of their roles in both plant defense and pathogen pathogenicity. A thorough understanding of the functions of PAs and conjugated PAs highlights their potential applications in fungicide development. The creation of new fungicides and compounds derived from PAs demonstrates their promising potential for further research and innovation in this field.

Advances in Understanding Fusarium graminearum: Genes Involved in the Regulation of Sexual Development, Pathogenesis, and Deoxynivalenol Biosynthesis

The wheat head blight disease caused by Fusarium graminearum is a major concern for food security and the health of both humans and animals. As a pathogenic microorganism, F. graminearum produces virulence factors during infection to increase pathogenicity, including various macromolecular and small molecular compounds. Among these virulence factors, secreted proteins and deoxynivalenol (DON) are important weapons for the expansion and colonization of F. graminearum. Besides the presence of virulence factors, sexual reproduction is also crucial for the infection process of F. graminearum and is indispensable for the emergence and spread of wheat head blight. Over the last ten years, there have been notable breakthroughs in researching the virulence factors and sexual reproduction of F. graminearum. This review aims to analyze the research progress of sexual reproduction, secreted proteins, and DON of F. graminearum, emphasizing the regulation of sexual reproduction and DON synthesis. We also discuss the application of new gene engineering technologies in the prevention and control of wheat head blight.

Multi-omics approaches to understand pathogenicity during potato early blight disease caused by Alternaria solani

Potato early blight (PEB), a foliar disease of potato during the growing period, caused by Alternaria sp., is common in major potato-producing areas worldwide. Effective agents to control this disease or completely resistant potato varieties are absent. Large-scale use of fungicides is limited due to possibility of increase in pathogen resistance and the requirements of ecological agriculture. In this study, we focused on the composition and infection characteristics of early blight pathogens in Yunnan Province and screened candidate pathogenesis-related pathways and genes. We isolated 85 strains of Alternaria sp. fungi from typical early blight spots in three potato-growing regions in Yunnan Province from 2018 to 2022, and identified 35 strains of Alternaria solani and 50 strains of Alternaria alternata by morphological characterization and ITS sequence comparison, which were identified as the main and conditional pathogens causing early blight in potato, respectively. Scanning electron microscope analysis confirmed only A. solani producing appressorium at 4 h after inoculation successfully infected the leaf cells. Via genome assembly and annotation, combine transcriptome and proteomic analysis, the following pathogenicity-related unit, transcription factors and metabolic pathway were identified: (1) cell wall-degrading enzymes, such as pectinase, keratinase, and cellulase; (2) genes and pathways related to conidia germination and pathogenicity, such as ubiquitination and peroxisomes; and (3) transcription factors, such as Zn-clus, C2H2, bZIP, and bHLH. These elements were responsible for PEB epidemic in Yunnan.

Intracellular polyamines regulate redox homeostasis with cAMP-PKA signalling during sexual mating/filamentation and pathogenicity of Sporisorium scitamineum

Sugarcane smut caused by Sporisorium scitamineum seriously impairs sugarcane production and quality. Sexual mating/filamentation is a critical step of S. scitamineum pathogenesis, yet the regulatory mechanisms are not fully understood. In this study, we identified the SsAGA, SsODC, and SsSAMDC genes, which are involved in polyamine biosynthesis in S. scitamineum. Deletion of SsODC led to complete loss of filamentous growth after sexual mating, and deletion of SsAGA or SsSAMDC caused reduced filamentation. Double deletion of SsODC and SsSAMDC resulted in auxotrophy for putrescine (PUT) and spermidine (SPD) when grown on minimal medium (MM), indicating that these two genes encode enzymes that are critical for PUT and SPD biosynthesis. We further showed that low PUT concentrations promoted S. scitamineum filamentation, while high PUT concentrations suppressed filamentation. Disrupted fungal polyamine biosynthesis also resulted in a loss of pathogenicity and reduced fungal biomass within infected plants at the early infection stage. SPD formed a gradient from the diseased part to nonsymptom parts of the cane stem, suggesting that SPD is probably favourable for fungal virulence. Mutants of the cAMP-PKA (SsGPA3-SsUAC1-SsADR1) signalling pathway displayed up-regulation of the SsODC gene and elevated intracellular levels of PUT. SsODC directly interacted with SsGPA3, and sporidia of the ss1uac1ΔodcΔ mutant displayed abundant pseudohyphae. Furthermore, we found that elevated PUT levels caused accumulation of intracellular reactive oxygen species (ROS), probably by suppressing transcription of ROS-scavenging enzymes, while SPD played the opposite role. Overall, our work proves that polyamines play important roles in the pathogenic development of sugarcane smut fungus, probably by collaboratively regulating intracellular redox homeostasis with the cAMP-PKA signalling pathway.

Isolation and characterization of extracellular vesicles from Fusarium oxysporum f. sp. cubense, a banana wilt pathogen

Fusarium wilt of banana is a destructive widespread disease caused by Fusarium oxysporum f. sp. cubense (Foc) that ravaged banana plantations globally, incurring huge economic losses. Current knowledge demonstrates the involvement of several transcription factors, effector proteins, and small RNAs in the Foc-banana interaction. However, the precise mode of communication at the interface remains elusive. Cutting-edge research has emphasized the significance of extracellular vesicles (EVs) in trafficking the virulent factors modulating the host physiology and defence system. EVs are ubiquitous inter- and intra-cellular communicators across kingdoms. This study focuses on the isolation and characterization of Foc EVs from methods that make use of sodium acetate, polyethylene glycol, ethyl acetate, and high-speed centrifugation. Isolated EVs were microscopically visualized using Nile red staining. Further, the EVs were characterized using transmission electron microscopy, which revealed the presence of spherical, double-membrane, vesicular structures ranging in size from 50 to 200 nm (diameter). The size was also determined using the principle based on Dynamic Light Scattering. The Foc EVs contained proteins that were separated using SDS-PAGE and ranged between 10 and 315 kDa. Mass spectrometry analysis revealed the presence of EV-specific marker proteins, toxic peptides, and effectors. The Foc EVs were found to be cytotoxic, whose toxicity increased with EVs isolated from the co-culture preparation. Taken together, a better understanding of Foc EVs and their cargo will aid in deciphering the molecular crosstalk between banana and Foc.