Genome-wide transcriptome analysis of toxigenic Fusarium verticillioides in response to variation of temperature and water activity on maize kernels.

Fusarium verticillioides is one of the important mycotoxigenic pathogens of maize since it causes severe yield losses and produces fumonisins (FBs) to threaten human and animal health. Previous studies showed that temperature and water activity (aw) are two pivotal environmental factors affecting F. verticillioides growth and FBs production during maize storage. However, the genome-wide transcriptome analysis of differentially expressed genes (DEGs) in F. verticillioides under the stress combinations of temperature and aw has not been studied in detail. In this study, DEGs of F. verticillioides and their related regulatory pathways were analyzed in response to the stress of temperature and aw combinations using RNA-Seq. The results showed that the optimal growth conditions for F. verticillioides were 0.98 aw and 25 °C, whereas the highest per-unit yield of the fumonisin B1 (FB1) was observed at 0.98 aw and 15 °C. The RNA-seq analysis showed that 9648 DEGs were affected by temperature regardless of aw levels, whereas only 218 DEGs were affected by aw regardless of temperature variations. Gene Ontology (GO) analysis revealed that a decrease in temperature at both aw levels led to a significant upregulation of genes associated with 24 biological processes, while three biological processes were downregulated. Furthermore, when aw was decreased at both temperatures, seven biological processes were significantly upregulated and four were downregulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the genes, whose expression was upregulated when the temperature decreased, were predominantly associated with the proteasome pathway, whereas the genes, whose expression was downregulated when the aw decreased, were mainly linked to amino acid metabolism. For the FB1, except for the FUM15 gene, the other 15 biosynthetic-related genes were highly expressed at 0.98 aw and 15 °C. In addition, the expression pattern analysis of other biosynthetic genes involved in secondary metabolite production and regulation of fumonisins production was conducted to explore how this fungus responds to the stress combinations of temperature and aw. Overall, this study primarily examines the impact of temperature and aw on the growth of F. verticillioides and its production of FB1 using transcriptome data. The findings presented here have the potential to contribute to the development of novel strategies for managing fungal diseases and offer valuable insights for preventing fumonisin contamination in food and feed storage.

Development and evaluation of a novel visual and rapid detection assay for toxigenic Fusarium graminearum in maize based on recombinase polymerase amplification and lateral flow analysis.

Maize ear rot caused by Fusarium graminearum is one of the most severe maize diseases in global maize-growing regions. It reduces maize yield in the field and is also responsible for mycotoxin contamination of grains during the postharvest period. F. graminearum is one of the major deoxynivalenol (DON), nivalenol (NIV), and zearalenone (ZEN) producers. The ingestion of these mycotoxins represents a risk for human and animal health. Hence, early detection and identification of F. graminearum are crucial to controlling these mycotoxins along the food or feed supply chains. In this study, the recombinase polymerase amplification with lateral flow dipstick (RPA-LFD) assay targeting the gaoA gene that codes for galactose oxidase was developed. The reaction conditions were optimized to make the method rapid, sensitive, and cost-effective. The developed RPA-LFD assay could detect the presence of 20 fg of the target genomic DNA per reaction within 25 min at 40 °C. Moreover, 52 field samples were tested using the developed RPA-LFD assay and compared with conventional PCR-based methods. The positive rate between RPA-LFD and the conventional PCR-based method was 100%. In conclusion, the developed method provides a novel alternative for the rapid, sensitive, and specific detection and identification of F. graminearum. It is not only workable for bulk maize samples without using sophisticated lab equipment but is also potentially useful for other agriculturally important toxigenic fungi.

Genome Sequence Resource of Fusarium brachygibbosum Padwick Strain HN-1, a Causal Agent of Maize Stalk Rot Disease.

Fusarium brachygibbosum Padwick, the causal agent of stalk rot disease, is a threat to the maize crop in China. However, genomic information of the pathogen is not available yet. The current study presented the genomic information of F. brachygibbosum, isolated from maize. The genome size is 40.36 Mb and consists of 12,510 genes. The GC content is 47.95%, and there are 913 predicted secretory proteins. The presented genomic data highlighted the virulence features, plant-microbe interaction ability, genes associated with the pathogen's metabolic processes, and host-binding ability. Presented results would extend our knowledge of the pathogen and help us develop suitable disease management strategies.