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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.


Effect of FgLAI12 on fungal biology.Mycelial growth of the WT, ΔFgLAI12 and C-FgLAI12 on mSNA-1 (A) and PDA plates (B) under treatment with LA and SA on the 4th, 6th and 8th days after inoculation. (C) Microscopic observation of mycelia growth within mSNA-1 plates supplemented with LA and SA. The depth of hyphae is marked with green lines. Agar plugs (0.5 cm2) cut from the edge of growing mycelia (Fig. 4A) were photographed with an Olympus SZ51 (Japan). (D) Comparison of conidial length, width and the number of septa of the WT, ΔFgLAI12 and C-FgLAI12. Different letters above each column indicate a significant difference (P < 0.05; n = 1000). The same rule as mentioned in the legend of Fig. 3 is used for indicating the significance within treatment, when there are more than one treatments in the same chart.
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f4: Effect of FgLAI12 on fungal biology.Mycelial growth of the WT, ΔFgLAI12 and C-FgLAI12 on mSNA-1 (A) and PDA plates (B) under treatment with LA and SA on the 4th, 6th and 8th days after inoculation. (C) Microscopic observation of mycelia growth within mSNA-1 plates supplemented with LA and SA. The depth of hyphae is marked with green lines. Agar plugs (0.5 cm2) cut from the edge of growing mycelia (Fig. 4A) were photographed with an Olympus SZ51 (Japan). (D) Comparison of conidial length, width and the number of septa of the WT, ΔFgLAI12 and C-FgLAI12. Different letters above each column indicate a significant difference (P < 0.05; n = 1000). The same rule as mentioned in the legend of Fig. 3 is used for indicating the significance within treatment, when there are more than one treatments in the same chart.

Mentions: To observe the changes in the growth phenotype caused by disruption of FgLAI12 in F. graminearum, the WT, ΔFgLAI12 and C-FgLAI12 strains were inoculated on modified Synthetischer Nährstoffarmer Agar-1 (mSNA-1) (Fig. 4A) and potato dextrose agar (PDA) plates (Fig. 4B). On mSNA-1 plates, ΔFgLAI12 formed much less aerial mycelium compared with WT and C-FgLAI12. On the 6th day after inoculation, aerial mycelium of ΔFgLAI12 was clearly observed (control in Fig. 4A). Similarly, ΔFgLAI12 mycelia grew more slowly than those of WT and C-FgLAI12 on PDA plates, as indicated on the 4th day after inoculation (control in Fig. 4B). Compared with the control, the spread of mycelia was inhibited by LA (LA treatment in Fig. 4A,B). Consistent with the role of FgLAI12 in LA metabolism, the spread and density of ΔFgLAI12 mycelia were more strongly inhibited by LA. Mycelial growth of ΔFgLAI12 was more sensitive to SA compared with that of WT and C-FgLAI12 (SA treatment in Fig. 4A,B). These results indicated that FgLAI12 plays important roles in mycelial growth and fungal response to SA.


Linoleic acid isomerase gene FgLAI12 affects sensitivity to salicylic acid, mycelial growth and virulence of Fusarium graminearum
Effect of FgLAI12 on fungal biology.Mycelial growth of the WT, ΔFgLAI12 and C-FgLAI12 on mSNA-1 (A) and PDA plates (B) under treatment with LA and SA on the 4th, 6th and 8th days after inoculation. (C) Microscopic observation of mycelia growth within mSNA-1 plates supplemented with LA and SA. The depth of hyphae is marked with green lines. Agar plugs (0.5 cm2) cut from the edge of growing mycelia (Fig. 4A) were photographed with an Olympus SZ51 (Japan). (D) Comparison of conidial length, width and the number of septa of the WT, ΔFgLAI12 and C-FgLAI12. Different letters above each column indicate a significant difference (P < 0.05; n = 1000). The same rule as mentioned in the legend of Fig. 3 is used for indicating the significance within treatment, when there are more than one treatments in the same chart.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Effect of FgLAI12 on fungal biology.Mycelial growth of the WT, ΔFgLAI12 and C-FgLAI12 on mSNA-1 (A) and PDA plates (B) under treatment with LA and SA on the 4th, 6th and 8th days after inoculation. (C) Microscopic observation of mycelia growth within mSNA-1 plates supplemented with LA and SA. The depth of hyphae is marked with green lines. Agar plugs (0.5 cm2) cut from the edge of growing mycelia (Fig. 4A) were photographed with an Olympus SZ51 (Japan). (D) Comparison of conidial length, width and the number of septa of the WT, ΔFgLAI12 and C-FgLAI12. Different letters above each column indicate a significant difference (P < 0.05; n = 1000). The same rule as mentioned in the legend of Fig. 3 is used for indicating the significance within treatment, when there are more than one treatments in the same chart.
Mentions: To observe the changes in the growth phenotype caused by disruption of FgLAI12 in F. graminearum, the WT, ΔFgLAI12 and C-FgLAI12 strains were inoculated on modified Synthetischer Nährstoffarmer Agar-1 (mSNA-1) (Fig. 4A) and potato dextrose agar (PDA) plates (Fig. 4B). On mSNA-1 plates, ΔFgLAI12 formed much less aerial mycelium compared with WT and C-FgLAI12. On the 6th day after inoculation, aerial mycelium of ΔFgLAI12 was clearly observed (control in Fig. 4A). Similarly, ΔFgLAI12 mycelia grew more slowly than those of WT and C-FgLAI12 on PDA plates, as indicated on the 4th day after inoculation (control in Fig. 4B). Compared with the control, the spread of mycelia was inhibited by LA (LA treatment in Fig. 4A,B). Consistent with the role of FgLAI12 in LA metabolism, the spread and density of ΔFgLAI12 mycelia were more strongly inhibited by LA. Mycelial growth of ΔFgLAI12 was more sensitive to SA compared with that of WT and C-FgLAI12 (SA treatment in Fig. 4A,B). These results indicated that FgLAI12 plays important roles in mycelial growth and fungal response to SA.

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.