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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.

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Schematic illustration of LA isomers.FgLAI12 is marked by a black box. PAI, Propionibacterium acnes cytosolic LA isomerase1011.
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f1: Schematic illustration of LA isomers.FgLAI12 is marked by a black box. PAI, Propionibacterium acnes cytosolic LA isomerase1011.

Mentions: Linoleic acid (LA; cis-9,cis-12 C18:2) plays an important role in wheat resistance to F. graminearum infection. Accumulation of LA is greater in FHB-resistant wheat lines than in susceptible lines6, suggesting that LA may contribute to FHB resistance. Enhanced accumulation of LA and other free fatty acids can reinforce the cuticle, which acts as a barrier to pathogen entry7. LA is metabolised by linoleate diol synthase (LDS)89 and linoleic acid isomerase (LAI) in fungi (Fig. 1). LDS has been well studied in fungi, and is involved in fungal development, reproduction, synthesis of trichothecenes and cytochrome metabolism891213. However, limited knowledge on LAI in fungi is available.


Linoleic acid isomerase gene FgLAI12 affects sensitivity to salicylic acid, mycelial growth and virulence of Fusarium graminearum
Schematic illustration of LA isomers.FgLAI12 is marked by a black box. PAI, Propionibacterium acnes cytosolic LA isomerase1011.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384231&req=5

f1: Schematic illustration of LA isomers.FgLAI12 is marked by a black box. PAI, Propionibacterium acnes cytosolic LA isomerase1011.
Mentions: Linoleic acid (LA; cis-9,cis-12 C18:2) plays an important role in wheat resistance to F. graminearum infection. Accumulation of LA is greater in FHB-resistant wheat lines than in susceptible lines6, suggesting that LA may contribute to FHB resistance. Enhanced accumulation of LA and other free fatty acids can reinforce the cuticle, which acts as a barrier to pathogen entry7. LA is metabolised by linoleate diol synthase (LDS)89 and linoleic acid isomerase (LAI) in fungi (Fig. 1). LDS has been well studied in fungi, and is involved in fungal development, reproduction, synthesis of trichothecenes and cytochrome metabolism891213. However, limited knowledge on LAI in fungi is available.

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 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.


Related in: MedlinePlus