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Linoleic acid isomerase gene FgLAI12 affects sensitivity to salicylic acid, mycelial growth and virulence of Fusarium graminearum

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ABSTRACT

Fusarium graminearum is the major causal agent of fusarium head blight in wheat, a serious disease worldwide. Linoleic acid isomerase (LAI) catalyses the transformation of linoleic acid (LA) to conjugated linoleic acid (CLA), which is beneficial for human health. We characterised a cis-12 LAI gene of F. graminearum (FGSG_02668; FgLAI12), which was downregulated by salicylic acid (SA), a plant defence hormone. Disruption of FgLAI12 in F. graminearum resulted in decreased accumulation of cis-9,trans-11 CLA, enhanced sensitivity to SA, and increased accumulation of LA and SA in wheat spikes during infection. In addition, mycelial growth, accumulation of deoxynivalenol, and pathogenicity in wheat spikes were reduced. Re-introduction of a functional FgLAI12 gene into ΔFgLAI12 recovered the wild-type phenotype. Fluorescent microscopic analysis showed that FgLAI12 protein was usually expressed in the septa zone of conidia and the vacuole of hyphae, but was expressed in the cell membrane of hyphae in response to exogenous LA, which may be an element of LA metabolism during infection by F. graminearum. The cis-12 LAI enzyme encoded by FgLAI12 is critical for fungal response to SA, mycelial growth and virulence in wheat. The gene FgLAI12 is potentially valuable for biotechnological synthesis of cis-9,trans-11 CLA.

No MeSH data available.


FgLAI12 encodes a cis-12 LA isomerase.(A) GC-MS analysis of chemicals derived from LA. (B) The peaks for LA, stearic acid and cis-9,trans-11 CLA when using standard chemicals. (C) Quantitative analysis of LA added to liquid medium containing growing mycelia. (D) Quantitative analysis of LA added to enzyme extract from mycelia. The same amount of mycelia was used. Different letters above each column indicate a significant difference (P < 0.05; n = 3). “a1, b1” and “a2, b2” are used to show the significance within WT and C-FgLAI12 treatments, respectively, since there are more than one treatments in the same chart.
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f3: FgLAI12 encodes a cis-12 LA isomerase.(A) GC-MS analysis of chemicals derived from LA. (B) The peaks for LA, stearic acid and cis-9,trans-11 CLA when using standard chemicals. (C) Quantitative analysis of LA added to liquid medium containing growing mycelia. (D) Quantitative analysis of LA added to enzyme extract from mycelia. The same amount of mycelia was used. Different letters above each column indicate a significant difference (P < 0.05; n = 3). “a1, b1” and “a2, b2” are used to show the significance within WT and C-FgLAI12 treatments, respectively, since there are more than one treatments in the same chart.

Mentions: Three peaks were detected in gas chromatography–mass spectrometry (GC-MS) analysis of compounds derived from LA (Fig. 3A), namely LA (the first peak), stearic acid (the second peak) and cis-9,trans-11 CLA (the third peak), by matching with GC-MS spectrometry gallery. The peaks for LA, stearic acid and cis-9,trans-11 CLA in GC-MS were confirmed by using of corresponding standard chemicals (Fig. 3B). In the presence of exogenous LA, enzyme extracts from mycelia of WT and C-FgLAI12 produced stearic acid and cis-9,trans-11 CLA, compared with no cis-9,trans-11 CLA and a small quantity of stearic acid for the extract from ΔFgLAI12. After addition of cis-9,trans-11 CLA, the enzyme extract from ΔFgLAI12 produced stearic acid as for the WT. FgLAI12 contains no known conserved domain of transcription factors, further suggesting that FgLAI12 is directly responsible for conversion of LA to cis-9,trans-11 CLA. These results showed that FgLAI12 encoded a LAI enzyme that catalysed the transformation of LA to cis-9,trans-11 CLA (Fig. 1), and that FgLAI12 played a major role in the isomerism of LA in F. graminearum under the experimental conditions.


Linoleic acid isomerase gene FgLAI12 affects sensitivity to salicylic acid, mycelial growth and virulence of Fusarium graminearum
FgLAI12 encodes a cis-12 LA isomerase.(A) GC-MS analysis of chemicals derived from LA. (B) The peaks for LA, stearic acid and cis-9,trans-11 CLA when using standard chemicals. (C) Quantitative analysis of LA added to liquid medium containing growing mycelia. (D) Quantitative analysis of LA added to enzyme extract from mycelia. The same amount of mycelia was used. Different letters above each column indicate a significant difference (P < 0.05; n = 3). “a1, b1” and “a2, b2” are used to show the significance within WT and C-FgLAI12 treatments, respectively, since there are more than one treatments in the same chart.
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Related In: Results  -  Collection

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f3: FgLAI12 encodes a cis-12 LA isomerase.(A) GC-MS analysis of chemicals derived from LA. (B) The peaks for LA, stearic acid and cis-9,trans-11 CLA when using standard chemicals. (C) Quantitative analysis of LA added to liquid medium containing growing mycelia. (D) Quantitative analysis of LA added to enzyme extract from mycelia. The same amount of mycelia was used. Different letters above each column indicate a significant difference (P < 0.05; n = 3). “a1, b1” and “a2, b2” are used to show the significance within WT and C-FgLAI12 treatments, respectively, since there are more than one treatments in the same chart.
Mentions: Three peaks were detected in gas chromatography–mass spectrometry (GC-MS) analysis of compounds derived from LA (Fig. 3A), namely LA (the first peak), stearic acid (the second peak) and cis-9,trans-11 CLA (the third peak), by matching with GC-MS spectrometry gallery. The peaks for LA, stearic acid and cis-9,trans-11 CLA in GC-MS were confirmed by using of corresponding standard chemicals (Fig. 3B). In the presence of exogenous LA, enzyme extracts from mycelia of WT and C-FgLAI12 produced stearic acid and cis-9,trans-11 CLA, compared with no cis-9,trans-11 CLA and a small quantity of stearic acid for the extract from ΔFgLAI12. After addition of cis-9,trans-11 CLA, the enzyme extract from ΔFgLAI12 produced stearic acid as for the WT. FgLAI12 contains no known conserved domain of transcription factors, further suggesting that FgLAI12 is directly responsible for conversion of LA to cis-9,trans-11 CLA. These results showed that FgLAI12 encoded a LAI enzyme that catalysed the transformation of LA to cis-9,trans-11 CLA (Fig. 1), and that FgLAI12 played a major role in the isomerism of LA in F. graminearum under the experimental conditions.

View Article: PubMed Central - PubMed

ABSTRACT

Fusarium graminearum is the major causal agent of fusarium head blight in wheat, a serious disease worldwide. Linoleic acid isomerase (LAI) catalyses the transformation of linoleic acid (LA) to conjugated linoleic acid (CLA), which is beneficial for human health. We characterised a cis-12 LAI gene of F. graminearum (FGSG_02668; FgLAI12), which was downregulated by salicylic acid (SA), a plant defence hormone. Disruption of FgLAI12 in F. graminearum resulted in decreased accumulation of cis-9,trans-11 CLA, enhanced sensitivity to SA, and increased accumulation of LA and SA in wheat spikes during infection. In addition, mycelial growth, accumulation of deoxynivalenol, and pathogenicity in wheat spikes were reduced. Re-introduction of a functional FgLAI12 gene into &Delta;FgLAI12 recovered the wild-type phenotype. Fluorescent microscopic analysis showed that FgLAI12 protein was usually expressed in the septa zone of conidia and the vacuole of hyphae, but was expressed in the cell membrane of hyphae in response to exogenous LA, which may be an element of LA metabolism during infection by F. graminearum. The cis-12 LAI enzyme encoded by FgLAI12 is critical for fungal response to SA, mycelial growth and virulence in wheat. The gene FgLAI12 is potentially valuable for biotechnological synthesis of cis-9,trans-11 CLA.

No MeSH data available.