Project description:Flavonoids are a group of hydroxylated polyphenolic compounds widely distributed in the plant kingdom. Biosynthesis of these compounds involves type III PKSs, whose presence has been recently predicted in some fungal species through genome sequencing efforts. In this study, for the first time it was found that Fusaria produce flavonoids on solid YES medium. Naringenin, as the central precursor of all flavonoids, was produced at highest quantities, followed by quercetin, kaempferol, apigenin and luteolin. In plants, flavonoids are involved in the protection of cereals to a wide range of stresses, including host defense against Fusaria. Under in vitro conditions, strains of Fusarium culmorum and F. graminearum sensu stricto were incubated at levels of flavonoids close to amounts produced by cereals in response to fungal infection. The amounts of exogenous naringenin, apigenin, luteolin, kaempferol and quercetin were reduced and converted by fungi to the other flavonoid derivatives. Treatment of fungi with naringenin derivatives led to the inhibition of naringenin production. Correspondingly, the production of fungal-derived phenolic acids decreased in flavonoid treated samples, although this effect appeared to be dependent on the strain, flavonoid molecule and its concentration. Fusaria showed high variability in trichothecene production in response to flavonoids. With emphasis on quercetin, mycotoxin accumulation in the media was significantly decreased by luteolin, kaempferol, naringenin and apigenin. However, in some cases, apigenin led to the increase of mycotoxin content in the media. Gene expression experiments of Tri genes responsible for trichothecene biosynthesis (Tri4, Tri5 and Tri10) proved that the inhibition of mycotoxin production by flavonoids occurred at the transcriptional level. However, the changes in Tri transcript levels were not significant in most apigenin and all kaempferol-treated cultures. In this study, a link was established between antioxidant and antiradical properties of flavonoids and their effects on fungi.

Project description:Fusarium verticillioides is a detrimental fungus that can contaminate maize grains with mycotoxins that are harmful to human and animal health. Breeding and growing resistant genotypes is one alternative to reduce contamination and subsequent production of mycotoxins by this fungus. However, little is known about the resistant mechanism relevant to breeding in this pathosystem. Therefore, our aim was to identify genes and metabolites that may be related to Fusarium ear rot resistance using resistant and susceptible maize inbreds. Kernels of the resistant inbred showed significantly reduced disease severity, and reduced levels of total fumonisin and ergosterol content compared with the susceptible one. Gene expression data were obtained from microarray hybridizations using F. verticillioides inoculated and non inoculated maize kernels. Differentially expressed sequences were identified and classified into 36 functional categories. Most of the differentially expressed genes were assigned to the categories “protein, RNA, DNA, stress, transport, signaling and cell metabolism”. These genes encode for PR proteins, detoxification and primary metabolism enzymes. Fungal inoculation did not produce considerable changes in gene expression and metabolites in the resistant L4637 inbred, probably due to a preformed or constitutive resistance mechanism. Defense-related genes were induced or repressed in kernels of the susceptible inbred L4674, responding specifically to the pathogen infection. The qRT-PCR in infected silks showed that glucanase, lipid transfer, xylanase inhibitor, PR1 and 26S proteosome transcripts had higher expression ratios in the susceptible line compared to the resistant one in response to fungal infection. Through this study, a global view of differential genes expressed and metabolites concentration during resistance and susceptibility to F. verticillioides inoculation has been obtained, giving additional information about the mechanisms and pathways conferring resistance to this important disease in maize.

Project description:Fusarium verticillioides is a detrimental fungus that can contaminate maize grains with mycotoxins that are harmful to human and animal health. Breeding and growing resistant genotypes is one alternative to reduce contamination and subsequent production of mycotoxins by this fungus. However, little is known about the resistant mechanism relevant to breeding in this pathosystem. Therefore, our aim was to identify genes and metabolites that may be related to Fusarium ear rot resistance using resistant and susceptible maize inbreds. Kernels of the resistant inbred showed significantly reduced disease severity, and reduced levels of total fumonisin and ergosterol content compared with the susceptible one. Gene expression data were obtained from microarray hybridizations using F. verticillioides inoculated and non inoculated maize kernels. Differentially expressed sequences were identified and classified into 36 functional categories. Most of the differentially expressed genes were assigned to the categories “protein, RNA, DNA, stress, transport, signaling and cell metabolism”. These genes encode for PR proteins, detoxification and primary metabolism enzymes. Fungal inoculation did not produce considerable changes in gene expression and metabolites in the resistant L4637 inbred, probably due to a preformed or constitutive resistance mechanism. Defense-related genes were induced or repressed in kernels of the susceptible inbred L4674, responding specifically to the pathogen infection. The qRT-PCR in infected silks showed that glucanase, lipid transfer, xylanase inhibitor, PR1 and 26S proteosome transcripts had higher expression ratios in the susceptible line compared to the resistant one in response to fungal infection. Through this study, a global view of differential genes expressed and metabolites concentration during resistance and susceptibility to F. verticillioides inoculation has been obtained, giving additional information about the mechanisms and pathways conferring resistance to this important disease in maize. Global view of differential genes expressed during resistance and susceptibility to F. verticillioides inoculation. Two maize inbred lines : one resistant (L4637) and one susceptible (L4674) to F. verticillioides infection. Two-condition experiment, Inoculated (I) vs. non-inoculated (NI) lines. Biological replicates: 3 . One replicate per array.

Dataset Information

Incidence and multiplex PCR based detection of trichothecene chemotypes of Fusarium culmorum isolates collected from freshly harvested Maize kernels in Southern India.

Publications

Incidence and multiplex PCR based detection of trichothecene chemotypes of Fusarium culmorum isolates collected from freshly harvested Maize kernels in Southern India.

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