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Maize EMBRYO SAC family peptides interact differentially with pollen tubes and fungal cells.

Woriedh M, Merkl R, Dresselhaus T - J. Exp. Bot. (2015)

Bottom Line: Furthermore, peptide fragments were found to bind differently to fungal cells.Mapping of peptide interaction sites identified amino acids differing in pollen tube burst and fungal response reactions.In summary, these findings indicate that residues targeting pollen tube burst in maize are specific to the ES family, while residues targeting fungal growth are conserved within defensins and defensin-like peptides.

View Article: PubMed Central - PubMed

Affiliation: Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany.

No MeSH data available.


Related in: MedlinePlus

Germination inhibition of F. graminearum and U. maydis after application of ES-c or ES-d peptides. Germination of F. graminearum conidia (A) and U. maydis spores (B) was measured spectrophotometrically at 595nm with PGM for 24h after application of peptides (see Fig. 1) at indicated concentrations. ES-c and ES-d show strong and comparable inhibition of germination. Error bars represent the standard error of nine independent experiments. (C) Application of 30 µM ES-d for 24h at conidia of F. graminearum-3xGFP resulted in growth suppression and swelling of mycelia (arrowheads) compared with (D) the control lacking peptides. (E) Application of 60 µM ES-d at spores of U. maydis-3xGFP resulted in strong suppression of germination compared with (F) the untreated control. Micrographs (C-F) show bright field at the left side and fluorescence at the right side. Scale bars are 20 µm in (C) and 50 µm in (D-F).
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Figure 4: Germination inhibition of F. graminearum and U. maydis after application of ES-c or ES-d peptides. Germination of F. graminearum conidia (A) and U. maydis spores (B) was measured spectrophotometrically at 595nm with PGM for 24h after application of peptides (see Fig. 1) at indicated concentrations. ES-c and ES-d show strong and comparable inhibition of germination. Error bars represent the standard error of nine independent experiments. (C) Application of 30 µM ES-d for 24h at conidia of F. graminearum-3xGFP resulted in growth suppression and swelling of mycelia (arrowheads) compared with (D) the control lacking peptides. (E) Application of 60 µM ES-d at spores of U. maydis-3xGFP resulted in strong suppression of germination compared with (F) the untreated control. Micrographs (C-F) show bright field at the left side and fluorescence at the right side. Scale bars are 20 µm in (C) and 50 µm in (D-F).

Mentions: Considering that maize ES1–4 are cysteine-rich peptide precursors belonging to the plant defensin/DEFL group, a fungal germination inhibitory assay was applied to study their antifungal activity and defence functions. Two maize fungal pathogens of different infection types were tested: the necrotrophic fungus F. graminearum and the biotrophic fungus U. maydis (CIMMYT, 2004; Dean et al., 2012). Thus, Fusarium conidia and Ustilago spores were inoculated in vitro with increasing concentrations of ES peptides. To quantify fungal biomass production and growth, F. graminearum-3xGFP and U. maydis-3xGFP strains that constitutively express triple versions of the gene for GFP were used. Fusarium conidia and Ustilago spores were inoculated in PGM, which was supplemented with varying concentrations of peptides. Peptide concentrations of 0.1–0.5 μM used for pollen tube burst assays did not show effects on fungal growth behaviour. However, strongly increased concentrations of 10–90 μM demonstrated a dose-dependent inhibition of germination after 24h. Remarkably, 90 μM of ES1 inhibited 66.7±1.1%, and ES4 inhibited 67.8±1.5% of the germination of Fusarium conidia, while ES-c inhibited 77.1±1.1% and ES-d inhibited 79.3±1.6% of conidia (P < 0.001). In Ustilago spores, 90 μM of ES1 inhibited 55.9±0.9% of germination and ES4 inhibited 56.4±0.9%, while ES-c inhibited 80.9±1.0% and ES-d inhibited 78.7±1.0% (P < 0.001). A significant inhibition was not observed for other small peptides and their variants (Fig. 4A, B). Conidia and spores showed a severely malformed appearance at a concentration of 90 µM of ES-c or ES-d. Approximately 80% of conidia and spores did not germinate at all, while the rest stopped growing after forming a short germination mycelium. Complete suppression of conidia and spore germination was observed at 120 μM. A peptide concentration of 10 µM resulted only in minor fungal growth differences. In contrast, at concentrations of 30–60 µM, a reduction in germination and fungal growth occurred, including severe swelling and malformed appearance (Fig. 4C-F). Moreover, Fusarium mycelium developed from germinated conidia failed to form hyphal colonies. Instead, they showed swelling and ballooning at mycelia tips, in comparison to untreated wild-type conidia, which showed development of normal long and thin filaments (Fig. 4C, D). Swelling and ballooning was not observed after peptides were applied to Ustilago spores, but germination of mycelium was strongly inhibited (Fig. 4E, F).


Maize EMBRYO SAC family peptides interact differentially with pollen tubes and fungal cells.

Woriedh M, Merkl R, Dresselhaus T - J. Exp. Bot. (2015)

Germination inhibition of F. graminearum and U. maydis after application of ES-c or ES-d peptides. Germination of F. graminearum conidia (A) and U. maydis spores (B) was measured spectrophotometrically at 595nm with PGM for 24h after application of peptides (see Fig. 1) at indicated concentrations. ES-c and ES-d show strong and comparable inhibition of germination. Error bars represent the standard error of nine independent experiments. (C) Application of 30 µM ES-d for 24h at conidia of F. graminearum-3xGFP resulted in growth suppression and swelling of mycelia (arrowheads) compared with (D) the control lacking peptides. (E) Application of 60 µM ES-d at spores of U. maydis-3xGFP resulted in strong suppression of germination compared with (F) the untreated control. Micrographs (C-F) show bright field at the left side and fluorescence at the right side. Scale bars are 20 µm in (C) and 50 µm in (D-F).
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Figure 4: Germination inhibition of F. graminearum and U. maydis after application of ES-c or ES-d peptides. Germination of F. graminearum conidia (A) and U. maydis spores (B) was measured spectrophotometrically at 595nm with PGM for 24h after application of peptides (see Fig. 1) at indicated concentrations. ES-c and ES-d show strong and comparable inhibition of germination. Error bars represent the standard error of nine independent experiments. (C) Application of 30 µM ES-d for 24h at conidia of F. graminearum-3xGFP resulted in growth suppression and swelling of mycelia (arrowheads) compared with (D) the control lacking peptides. (E) Application of 60 µM ES-d at spores of U. maydis-3xGFP resulted in strong suppression of germination compared with (F) the untreated control. Micrographs (C-F) show bright field at the left side and fluorescence at the right side. Scale bars are 20 µm in (C) and 50 µm in (D-F).
Mentions: Considering that maize ES1–4 are cysteine-rich peptide precursors belonging to the plant defensin/DEFL group, a fungal germination inhibitory assay was applied to study their antifungal activity and defence functions. Two maize fungal pathogens of different infection types were tested: the necrotrophic fungus F. graminearum and the biotrophic fungus U. maydis (CIMMYT, 2004; Dean et al., 2012). Thus, Fusarium conidia and Ustilago spores were inoculated in vitro with increasing concentrations of ES peptides. To quantify fungal biomass production and growth, F. graminearum-3xGFP and U. maydis-3xGFP strains that constitutively express triple versions of the gene for GFP were used. Fusarium conidia and Ustilago spores were inoculated in PGM, which was supplemented with varying concentrations of peptides. Peptide concentrations of 0.1–0.5 μM used for pollen tube burst assays did not show effects on fungal growth behaviour. However, strongly increased concentrations of 10–90 μM demonstrated a dose-dependent inhibition of germination after 24h. Remarkably, 90 μM of ES1 inhibited 66.7±1.1%, and ES4 inhibited 67.8±1.5% of the germination of Fusarium conidia, while ES-c inhibited 77.1±1.1% and ES-d inhibited 79.3±1.6% of conidia (P < 0.001). In Ustilago spores, 90 μM of ES1 inhibited 55.9±0.9% of germination and ES4 inhibited 56.4±0.9%, while ES-c inhibited 80.9±1.0% and ES-d inhibited 78.7±1.0% (P < 0.001). A significant inhibition was not observed for other small peptides and their variants (Fig. 4A, B). Conidia and spores showed a severely malformed appearance at a concentration of 90 µM of ES-c or ES-d. Approximately 80% of conidia and spores did not germinate at all, while the rest stopped growing after forming a short germination mycelium. Complete suppression of conidia and spore germination was observed at 120 μM. A peptide concentration of 10 µM resulted only in minor fungal growth differences. In contrast, at concentrations of 30–60 µM, a reduction in germination and fungal growth occurred, including severe swelling and malformed appearance (Fig. 4C-F). Moreover, Fusarium mycelium developed from germinated conidia failed to form hyphal colonies. Instead, they showed swelling and ballooning at mycelia tips, in comparison to untreated wild-type conidia, which showed development of normal long and thin filaments (Fig. 4C, D). Swelling and ballooning was not observed after peptides were applied to Ustilago spores, but germination of mycelium was strongly inhibited (Fig. 4E, F).

Bottom Line: Furthermore, peptide fragments were found to bind differently to fungal cells.Mapping of peptide interaction sites identified amino acids differing in pollen tube burst and fungal response reactions.In summary, these findings indicate that residues targeting pollen tube burst in maize are specific to the ES family, while residues targeting fungal growth are conserved within defensins and defensin-like peptides.

View Article: PubMed Central - PubMed

Affiliation: Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany.

No MeSH data available.


Related in: MedlinePlus