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Fumigation and contact activities of 18 plant essential oils on Villosiclava virens, the pathogenic fungus of rice false smut.

ABSTRACT: Rice false smut (RFS), caused by Villosiclava virens, is an emerging devastating disease of rice panicles worldwide and produces yield loss and mycotoxin residues in rice. In this study, 18 plant essential oils (PEOs) were selected to evaluate antifungal activity via fumigation and contact methods against the mycelial growth and conidial germination of V. virens. The primary compositions of PEOs with stronger fungistatic activity were analyzed using gas chromatography (GC)-mass spectrometry (MS), and the changes in the mycelial morphology were observed using scanning electron microscopy (SEM). Antifungal tests showed that cinnamon bark oil and cinnamon oil had stronger fumigation and contact effects on V. virens than the other oils tested. The primary active composition in both cinnamon bark oil and cinnamon oil was trans-cinnamaldehyde, which exhibited contact activities with EC₅₀ values of 2.13 and 35.9??g/mL against mycelial growth and conidial germination, respectively. The hyphae surface morphological alterations caused by cinnamon bark oil, cinnamon oil and trans-cinnamaldehyde included shriveling, vacuolation and exfoliation. In conclusion, cinnamon bark oil and cinnamon oil have the potential to prevent and control RFS, and trans-cinnamaldehyde is a promising natural lead compound for new fungicide discoveries to control RFS contamination and mycotoxin residues in rice.

SUBMITTER: Zheng J

PROVIDER: S-EPMC6517416 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Fumigation and contact activities of 18 plant essential oils on Villosiclava virens, the pathogenic fungus of rice false smut.

Zheng Jingge J Liu Tingting T Guo Zhixin Z Zhang Lan L Mao Liangang L Zhang Yanning Y Jiang Hongyun H

Scientific reports 20190514 1

Rice false smut (RFS), caused by Villosiclava virens, is an emerging devastating disease of rice panicles worldwide and produces yield loss and mycotoxin residues in rice. In this study, 18 plant essential oils (PEOs) were selected to evaluate antifungal activity via fumigation and contact methods against the mycelial growth and conidial germination of V. virens. The primary compositions of PEOs with stronger fungistatic activity were analyzed using gas chromatography (GC)-mass spectrometry (MS) ...[more]

PMID: 31089151

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Project description:BACKGROUND: Rice false smut caused by Villosiclava virens is a devastating fungal disease that spreads in major rice-growing regions throughout the world. However, the genomic information for this fungal pathogen is limited and the pathogenic mechanism of this disease is still not clear. To facilitate genetic, molecular and genomic studies of this fungal pathogen, we constructed the first BAC-based physical map and performed the first genome survey for this species. RESULTS: High molecular weight genomic DNA was isolated from young mycelia of the Villosiclava virens strain UV-8b and a high-quality, large-insert and deep-coverage Bacterial Artificial Chromosome (BAC) library was constructed with the restriction enzyme HindIII. The BAC library consisted of 5,760 clones, which covers 22.7-fold of the UV-8b genome, with an average insert size of 140 kb and an empty clone rate of lower than 1%. BAC fingerprinting generated successful fingerprints for 2,290 BAC clones. Using the fingerprints, a whole genome-wide BAC physical map was constructed that contained 194 contigs (2,035 clones) spanning 51.2 Mb in physical length. Bidirectional-end sequencing of 4,512 BAC clones generated 6,560 high quality BAC end sequences (BESs), with a total length of 3,030,658 bp, representing 8.54% of the genome sequence. Analysis of the BESs revealed general genome information, including 51.52% GC content, 22.51% repetitive sequences, 376.12/Mb simple sequence repeat (SSR) density and approximately 36.01% coding regions. Sequence comparisons to other available fungal genome sequences through BESs showed high similarities to Metarhizium anisopliae, Trichoderma reesei, Nectria haematococca and Cordyceps militaris, which were generally in agreement with the 18S rRNA gene analysis results. CONCLUSION: This study provides the first BAC-based physical map and genome information for the important rice fungal pathogen Villosiclava virens. The BAC clones, physical map and genome information will serve as fundamental resources to accelerate the genetic, molecular and genomic studies of this pathogen, including positional cloning, comparative genomic analysis and whole genome sequencing. The BAC library and physical map have been opened to researchers as public genomic resources (http://gresource.hzau.edu.cn/resource/resource.html).

Project description:False smut, caused by Villosiclava virens, is becoming increasingly serious in modern rice production systems, leading to yield losses and quality declines. Successful infection requires efficient acquisition of sucrose, abundant in rice panicles, as well as other sugars. Sugar transporters (STPs) may play an important role in this process. STPs belong to a major facilitator superfamily, which consists of large multigenic families necessary to partition sugars between fungal pathogens and their hosts. This study identified and characterized the STP family of V. viren, and further analyzed their gene functions to uncover their roles in interactions with rice. Through genome-wide and systematic bioinformatics analyses, 35 STPs were identified from V.virens and named from VvSTP1 to VvSTP35. Transmembrane domains, gene structures, and conserved motifs of VvSTPs have been identified and characterized through the bioinformatic analysis. In addition, a phylogenetic analysis revealed relationship between VvSTPs and STPs from the other three reference fungi. According to a qRT-PCR and RNA-sequencing analysis, VvSTP expression responded differently to different sole carbon sources and H2O2 treatments, and changed during the pathogenic process, suggesting that these proteins are involved in interactions with rice and potentially functional in pathogenesis. In total, 12 representative VvSTPs were knocked out through genetic recombination in order to analyze their roles in pathogenicity of V. virens. The knock-out mutants of VvSTPs showed little difference in mycelia growth and conidiation, indicating a single gene in this family cannot influence vegetative growth of V. virens. It is clear, however, that these mutants result in a change in infection efficiency in a different way, indicating that VvSTPs play an important role in the pathogenicity of virens. This study is expected to contribute to a better understanding of how host-derived sugars contribute to V. virens pathogenicity.

Project description:Rice false smut, caused by the fungal pathogen Ustilaginoidea virens, is a worldwide rice fungal disease. However, the molecular mechanism of the pathogenicity of the fungus U. virens remains unclear. To understand the molecular mechanism of pathogenesis of the fungus U. virens, we performed an integrated analysis of the transcriptome and metabolome of strongly (S) and weakly (W) virulent strains both before and after the infection of panicles. A total of 7932 differential expressed genes (DEGs) were identified using transcriptome analysis. Gene ontology (GO) and metabolic pathway enrichment analysis indicated that amino acid metabolism, autophagy-yeast, MAPK signaling pathway-yeast, and starch and sucrose metabolism were closely related to the pathogenicity of U. virens. Genes related to pathogenicity were significantly upregulated in the strongly virulent strain, and were ATG, MAPK, STE, TPS, and NTH genes. However, genes involved in the negative regulation of pathogenesis were significantly downregulated and contained TOR kinase, TORC1, and autophagy-related protein genes. Metabolome analysis identified 698 differentially accumulated metabolites (DAMs), including 13 categories of organic acids and derivatives, lipids and lipid-like molecules, organoheterocyclic compounds. The significantly enriched pathways of DAMs mainly included amino acids and carbohydrates, and they accumulated after infection by the S strain. To understand the relevance of DEGs and DAMs in the pathogenicity of U. virens, transcriptomic and metabolomic data were integrated and analyzed. These results further confirmed that the pathogenesis of U. virens was regulated by DEGs and DAMs related to these four pathways, involving arginine and proline metabolism, lysine biosynthesis, alanine, aspartate and glutamate metabolism, and starch and sugar metabolism. Therefore, we speculate that the pathogenicity of U. virens is closely related to the accumulation of amino acids and carbohydrates, and to the changes in the expression of related genes.

Dataset Information

Fumigation and contact activities of 18 plant essential oils on Villosiclava virens, the pathogenic fungus of rice false smut.

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Fumigation and contact activities of 18 plant essential oils on Villosiclava virens, the pathogenic fungus of rice false smut.

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