Food security is a global concern. Fusarium are among the most economically important fungal pathogens because they are ubiquitous, disease management remains a challenge, they produce mycotoxins that affect food and feed safety, and trichothecene mycotoxin production can increase the pathogenicity of some Fusarium species depending on the host species. Although trichothecenes may differ in structure by their patterns of hydroxylation or acetylation, these small changes have a significant impact on toxicity and the biological activity of these compounds. Therefore, detecting and identifying which chemotype is present in a given population are important to predicting the specific toxins that may be produced and, therefore, to evaluating the risk of exposure. Due to the challenges of inducing trichothecene production by Fusarium isolates in vitro for subsequent chemical analysis, PCR assays using gene-specific primers, either singly or in combination, designed against specific genes of the trichothecene gene cluster of multiple species of Fusarium have been developed. The establishment of TRI genotypes that potentially correspond to a specific chemotype requires examination of an information and knowledge pipeline whose critical aspects in sequential order are: (i) understanding the TRI gene cluster organization which differs according to Fusarium species under study; (ii) knowledge of the re-arrangements to the core TRI gene cluster over evolutionary time, which also differs according to Fusarium species; (iii) the functions of the TRI genes in the biosynthesis of trichothecene analogs; and (iv) based on (i)–(iii), selection of appropriate target TRI gene(s) for primer design in PCR amplification for the Fusarium species under study. This review, therefore, explains this pipeline and its connection to utilizing TRI genotypes as a possible proxy to chemotype designation.
Fusarium is among the top 10 most economically important plant pathogens in the world. Trichothecenes are the principal mycotoxins produced as secondary metabolites by select species of Fusarium and cause acute and chronic toxicity in animals and humans upon exposure either through consumption and/or contact. There are over 100 trichothecene metabolites and they can occur in a wide range of commodities that form food and feed products. This review discusses strategies to mitigate the risk of mycotoxin production and exposure by examining the Fusarium-trichothecene model. Fundamental to mitigation of risk is knowing the identity of the pathogen. As such, a comparison of current, recommended molecular approaches for sequence-based identification of Fusaria is presented, followed by an analysis of the rationale and methods of trichothecene (TRI) genotyping and chemotyping. This type of information confirms the source and nature of risk. While both are powerful tools for informing regulatory decisions, an assessment of the causes of incongruence between TRI genotyping and chemotyping data must be made. Reconciliation of this discordance will map the way forward in terms of optimization of molecular approaches, which includes data validation and sharing in the form of accessible repositories of genomic data and browsers for querying such data.
Trichothecene mycotoxins are a class of secondary metabolites produced by multiple genera of fungi, including certain plant pathogenic Fusarium species. Functional variation in the TRI1 gene produces a novel Type A trichothecene called NX-2 in strains of F. graminearum. Using a bioinformatics approach, a systematic analysis of 52 translated TRI1 sequences of Fusarium species, including five F. graminearum NX-2 producers and four F. graminearum non-NX-2 producers, was conducted to explain the functional difference of TRI1p of FGNX-2. An assessment of several signature motifs of fungal P450s revealed amino acid substitutions in addition to the post-translational N-X-S/T sequons motif, which is indicative of N-linked glycosylation of this TRI1-encoded protein characteristic of NX-2 producers. There was evidence of selection bias, where TRI1 gene sequences were found to be under positive selection and, therefore, under functional constraints. The cumulative amino acid changes in the TRI1p sequences were reflected in the phylogenetic analyses which revealed species-specific clustering with a distinct separation of FGNX-2 from FG-non-NX-2 producers with high bootstrap support. Together, our findings provide insight into the amino acid sequence features responsible for the functional diversification of this TRI1p.
The Fusarium incarnatum-equiseti species complex (FIESC) consists of 33 phylogenetic species according to multi-locus sequence typing (MLST) and Genealogical Concordance Phylogenetic Species Recognition (GCPSR). A multi-locus dataset consisting of nucleotide sequences of the translation elongation factor (EF-1α), calmodulin (CAM), partial RNA polymerase largest subunit (RPB1), and partial RNA polymerase second largest subunit (RPB2), was generated to distinguish among phylogenetic species within the FIESC isolates infecting bell pepper in Trinidad. Three phylogenetic species belonged to the Incarnatum clade , and one species belonged to the Equiseti clade . Specific MLST types were sensitive to 10 µg/mL of tebuconazole fungicide as a discriminatory dose. The EC50 values were significantly different among the four MLST groups, which were separated into two homogeneous groups: FIESC-26a and FIESC-14a, demonstrating the "sensitive" azole phenotype and FIESC-15a and FIESC-16a as the "less sensitive" azole phenotype. CYP51C sequences of the Trinidad isolates, although under positive selection, were without any signatures of recombination, were highly conserved, and were not correlated with these azole phenotypes. CYP51C sequences were unable to resolve the FIESC isolates as phylogenetic inference indicated polytomic branching for these sequences. This data is important to different research communities, including those studying Fusarium phytopathology, mycotoxins, and public health impacts.
Colletotrichum species complexes are among the top 10 economically important fungal plant pathogens worldwide because they can infect climacteric and nonclimacteric fruit at the pre and/or postharvest stages. C. truncatum is the major pathogen responsible for anthracnose of green and red bell pepper fruit worldwide. C. brevisporum was recently reported to be a minor pathogen of red bell pepper fruit in Trinidad, but has recently been reported as pathogenic to other host species in other countries. The ability of these phytopathogens to produce and secrete cutinase is required for dismantling the cuticle of the host plant and, therefore, crucial to the necrotrophic phase of their infection strategy. In vitro bioassays using different lipid substrates confirmed the ability of C. truncatum and C. brevisporum isolates from green and red bell peppers to secrete cutinase. The diversity, structure and organization and synteny of the cutinase gene were determined among different Colletotrichum species. Cluster analysis indicated a low level of nucleotide variation among C. truncatum sequences. Nucleotide sequences of C. brevisporum were more related to C. truncatum cutinase nucleotide sequences than to C. gloeosporioides. Cluster patterns coincided with haplotype and there was evidence of significant positive selection with no recombination signatures. The structure of the cutinase gene included two exons with one intervening intron and, therefore, one splice variant. Although amino acid sequences were highly conserved among C. truncatum isolates, diversity “hot spots” were revealed when the 66‐amino acid coding region of 200 fungal species was compared. Twenty cutinase orthologues were detected among different fungal species, whose common ancestor is Pezizomycotina and it is purported that these orthologues arose through a single gene duplication event prior to speciation. The cutinase domain was retained both in structure and arrangement among 34 different Colletotrichum species. The order of aligned genomic blocks between species and the arrangement of flanking protein domains were also conserved and shared for those domains immediately located at the N‐ and C‐terminus of the cutinase domain. Among these were an RNA recognition motif, translation elongation factor, signal peptide, pentatricopeptide repeat, and Hsp70 family of chaperone proteins, all of which support the expression of the cutinase gene. The findings of this study are important to understanding the evolution of the cutinase gene in C. truncatum as a key component of the biotrophic–necrotrophic switch which may be useful in developing gene‐targeting strategies to decrease the pathogenic potential of Colletotrichum species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.