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LDS1-produced oxylipins are negative regulators of growth, conidiation and fumonisin synthesis in the fungal maize pathogen Fusarium verticillioides.

Scala V, Giorni P, Cirlini M, Ludovici M, Visentin I, Cardinale F, Fabbri AA, Fanelli C, Reverberi M, Battilani P, Galaverna G, Dall'Asta C - Front Microbiol (2014)

Bottom Line: Among the many enzymes responsible for oxylipin generation, Linoleate Diol Synthase 1 (LDS1) produces mainly 8-hydroperoxyoctadecenoic acid and subsequently different di-hydroxyoctadecenoic acids.In this study, we inactivated a copy of the putative LDS1 ortholog (acc.We hypothesize that oxylipins may act as regulators of gene expression in the toxigenic plant pathogen F. verticillioides, in turn causing notable changes in its phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Biology, University of Rome "Sapienza" Rome, Italy.

ABSTRACT
Oxylipins are fatty acid-derived signaling compounds produced by all eukaryotes so far investigated; in mycotoxigenic fungi, they modulate toxin production and interactions with the host plants. Among the many enzymes responsible for oxylipin generation, Linoleate Diol Synthase 1 (LDS1) produces mainly 8-hydroperoxyoctadecenoic acid and subsequently different di-hydroxyoctadecenoic acids. In this study, we inactivated a copy of the putative LDS1 ortholog (acc. N. FVEG_09294.3) of Fusarium verticillioides, with the aim to investigate its influence on the oxylipin profile of the fungus, on its development, secondary metabolism and virulence. LC-MS/MS oxylipin profiling carried out on the selected mutant strain revealed significant quali-quantitative differences for several oxylipins when compared to the WT strain. The Fvlds1-deleted mutant grew better, produced more conidia, synthesized more fumonisins and infected maize cobs faster than the WT strain. We hypothesize that oxylipins may act as regulators of gene expression in the toxigenic plant pathogen F. verticillioides, in turn causing notable changes in its phenotype. These changes could relate to the ability of oxylipins to re-shape the transcriptional profile of F. verticillioides by inducing chromatin modifications and exerting a direct control on the transcription of secondary metabolism in fungi.

No MeSH data available.


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(A–F) mRNA levels of fungal and plant genes in infected cobs. F. verticillioides LDS1(A), LDS2(B), LDS3(C), and LOX(D), Zea mays LOX3(E), and PR4(F) were quantified at 2–15 DAI in maize cobs non-inoculated (mock), or inoculated with the WT or mutant strain (ΔFvlds1D). Relative mRNA expression is calculated by using the 2−ΔΔCt method, i.e., by normalizing gene of interest expression onto housekeeping gene expression and to their value at the time of inoculation (time zero). Results are the mean (± SE) of six replications deriving from two independent experiments.
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Figure 5: (A–F) mRNA levels of fungal and plant genes in infected cobs. F. verticillioides LDS1(A), LDS2(B), LDS3(C), and LOX(D), Zea mays LOX3(E), and PR4(F) were quantified at 2–15 DAI in maize cobs non-inoculated (mock), or inoculated with the WT or mutant strain (ΔFvlds1D). Relative mRNA expression is calculated by using the 2−ΔΔCt method, i.e., by normalizing gene of interest expression onto housekeeping gene expression and to their value at the time of inoculation (time zero). Results are the mean (± SE) of six replications deriving from two independent experiments.

Mentions: Fungal pathogens as well as host plants produce oxylipins during the interaction. The shared chemical structure is at the basis of their mutual ability to affect defense onset (in the host) and virulence (in the fungus) (Christensen and Kolomiets, 2011). We analyzed the expression of some fungal oxylipin-related genes and one of the most studied maize genes (ZmLOX3) coding for LOX enzymes and known to be important in the interaction of maize with other mycotoxin-producing fungi (Gao et al., 2009). In particular, we monitored the expression of fungal LDS1-3 and LOX as well as of maize ZmLOX3 (Figures 5A–E) in maize cobs artificially inoculated. As reported in Figure 5A, total FvLDS1 transcript (LDS1a plus b) is conspicuously less abundant, but not completely absent, in the ΔFvlds1D strain as compared to the WT. Since we deleted only one out of the two LDS1 copies present in the genome of our parental strain, the results suggest that the non-deleted copy LDS1a may be expressed in vivo (Figure 5A) while it is not in vitro (see Figure 2A for comparison). The transcript abundance of other oxylipin-related genes was similar (LDS2, Figure 5B) or higher (LDS3, LOX, Figures 5C,D) in the ΔFvlds1D strain when compared to the WT. It is noteworthy that while LDS2 and LDS3 were down-regulated under in vitro conditions at all time-points (p < 0.01), both are up-regulated in vivo, likely upon the influence of the host tissues. Conversely, FvLOX expression was consistently up-regulated in the ΔFvlds1D strain as compared to the WT (p < 0.001), even more conspicuously than under in vitro conditions (see Figure 2D for comparison).


LDS1-produced oxylipins are negative regulators of growth, conidiation and fumonisin synthesis in the fungal maize pathogen Fusarium verticillioides.

Scala V, Giorni P, Cirlini M, Ludovici M, Visentin I, Cardinale F, Fabbri AA, Fanelli C, Reverberi M, Battilani P, Galaverna G, Dall'Asta C - Front Microbiol (2014)

(A–F) mRNA levels of fungal and plant genes in infected cobs. F. verticillioides LDS1(A), LDS2(B), LDS3(C), and LOX(D), Zea mays LOX3(E), and PR4(F) were quantified at 2–15 DAI in maize cobs non-inoculated (mock), or inoculated with the WT or mutant strain (ΔFvlds1D). Relative mRNA expression is calculated by using the 2−ΔΔCt method, i.e., by normalizing gene of interest expression onto housekeeping gene expression and to their value at the time of inoculation (time zero). Results are the mean (± SE) of six replications deriving from two independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263177&req=5

Figure 5: (A–F) mRNA levels of fungal and plant genes in infected cobs. F. verticillioides LDS1(A), LDS2(B), LDS3(C), and LOX(D), Zea mays LOX3(E), and PR4(F) were quantified at 2–15 DAI in maize cobs non-inoculated (mock), or inoculated with the WT or mutant strain (ΔFvlds1D). Relative mRNA expression is calculated by using the 2−ΔΔCt method, i.e., by normalizing gene of interest expression onto housekeeping gene expression and to their value at the time of inoculation (time zero). Results are the mean (± SE) of six replications deriving from two independent experiments.
Mentions: Fungal pathogens as well as host plants produce oxylipins during the interaction. The shared chemical structure is at the basis of their mutual ability to affect defense onset (in the host) and virulence (in the fungus) (Christensen and Kolomiets, 2011). We analyzed the expression of some fungal oxylipin-related genes and one of the most studied maize genes (ZmLOX3) coding for LOX enzymes and known to be important in the interaction of maize with other mycotoxin-producing fungi (Gao et al., 2009). In particular, we monitored the expression of fungal LDS1-3 and LOX as well as of maize ZmLOX3 (Figures 5A–E) in maize cobs artificially inoculated. As reported in Figure 5A, total FvLDS1 transcript (LDS1a plus b) is conspicuously less abundant, but not completely absent, in the ΔFvlds1D strain as compared to the WT. Since we deleted only one out of the two LDS1 copies present in the genome of our parental strain, the results suggest that the non-deleted copy LDS1a may be expressed in vivo (Figure 5A) while it is not in vitro (see Figure 2A for comparison). The transcript abundance of other oxylipin-related genes was similar (LDS2, Figure 5B) or higher (LDS3, LOX, Figures 5C,D) in the ΔFvlds1D strain when compared to the WT. It is noteworthy that while LDS2 and LDS3 were down-regulated under in vitro conditions at all time-points (p < 0.01), both are up-regulated in vivo, likely upon the influence of the host tissues. Conversely, FvLOX expression was consistently up-regulated in the ΔFvlds1D strain as compared to the WT (p < 0.001), even more conspicuously than under in vitro conditions (see Figure 2D for comparison).

Bottom Line: Among the many enzymes responsible for oxylipin generation, Linoleate Diol Synthase 1 (LDS1) produces mainly 8-hydroperoxyoctadecenoic acid and subsequently different di-hydroxyoctadecenoic acids.In this study, we inactivated a copy of the putative LDS1 ortholog (acc.We hypothesize that oxylipins may act as regulators of gene expression in the toxigenic plant pathogen F. verticillioides, in turn causing notable changes in its phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Biology, University of Rome "Sapienza" Rome, Italy.

ABSTRACT
Oxylipins are fatty acid-derived signaling compounds produced by all eukaryotes so far investigated; in mycotoxigenic fungi, they modulate toxin production and interactions with the host plants. Among the many enzymes responsible for oxylipin generation, Linoleate Diol Synthase 1 (LDS1) produces mainly 8-hydroperoxyoctadecenoic acid and subsequently different di-hydroxyoctadecenoic acids. In this study, we inactivated a copy of the putative LDS1 ortholog (acc. N. FVEG_09294.3) of Fusarium verticillioides, with the aim to investigate its influence on the oxylipin profile of the fungus, on its development, secondary metabolism and virulence. LC-MS/MS oxylipin profiling carried out on the selected mutant strain revealed significant quali-quantitative differences for several oxylipins when compared to the WT strain. The Fvlds1-deleted mutant grew better, produced more conidia, synthesized more fumonisins and infected maize cobs faster than the WT strain. We hypothesize that oxylipins may act as regulators of gene expression in the toxigenic plant pathogen F. verticillioides, in turn causing notable changes in its phenotype. These changes could relate to the ability of oxylipins to re-shape the transcriptional profile of F. verticillioides by inducing chromatin modifications and exerting a direct control on the transcription of secondary metabolism in fungi.

No MeSH data available.


Related in: MedlinePlus