Binding of Barley and Wheat α-Thionins to Polysaccharides

Oita, Shigeru; Ohnishi‐Kameyama, Mayumi; Nagata, Takayuki

doi:10.1271/bbb.64.958

Cited by 23 publications

(10 citation statements)

References 23 publications

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“…AFP1, an antifungal protein from Streptomyces tendae, was found to bind to chitin, which caused severe alterations in cell morphogenesis (1). Additionally, binding of alpha-thionins from barley and wheat to polysaccharides containing beta-1,3-glucan, which are present in fungal cell walls, has been reported (21). Using the SYTOX Green assay, we were able to show that AFP causes the membranes of AFPsensitive fungi to become permeable.…”

Section: Discussionmentioning

confidence: 85%

The Antifungal Protein from Aspergillus giganteus Causes Membrane Permeabilization

Theis

Wedde

Meyer

et al. 2003

Antimicrob Agents Chemother

104

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We investigated the inhibitory effects of the antifungal protein (AFP) from Aspergillus giganteus on the growth of several filamentous fungi. For this purpose, the MICs of AFP were determined and ranged from 0.1 g/ml for Fusarium oxysporum to 200 g/ml for Aspergillus nidulans. The antifungal activity of AFP was diminished in the presence of cations. We were able to show that incubation of AFP-sensitive fungi with the protein resulted in membrane permeabilization using an assay based on the uptake of the fluorescent dye SYTOX Green. No permeabilization by AFP could be detected at concentrations below the species-specific MIC. Furthermore, AFP-induced permeabilization could readily be detected after 5 min of incubation. Localization experiments with fluorescein isothiocyanate-labeled AFP and immunofluorescence staining with an AFP-specific antibody supported the observation that the protein interacts with membranes. After treatment of AFP-sensitive fungi with AFP, the protein was localized at the plasma membrane, whereas it was mainly detected inside the cells of AFP-resistant fungi. We conclude from these data that the growth-inhibitory effect of AFP is caused by permeabilization of the fungal membranes.The imperfect filamentous fungus Aspergillus giganteus was found to secrete two small basic proteins, namely, the antifungal protein (AFP) and ␣-sarcin (22). ␣-Sarcin is a cytotoxic protein belonging to the ribotoxins, a family of ribosome-inactivating proteins (2,6,7,13,17,24,30). AFP is a highly basic polypeptide of 51 amino acids with a high content of cysteine, tyrosine, and lysine residues. The isoelectric point was estimated to be 8.8; thus, the protein is positively charged under neutral conditions. AFP is folded into five highly twisted antiparallel strands, defining a small and compact structure with four stabilizing disulfide bridges (3,20,29).Only three small, basic antifungal proteins have been isolated from filamentous fungi to date: AFP from A. giganteus (22), PAF from Penicillium chrysogenum (18), and Anafp from Aspergillus niger (14). Recently, the naf gene was isolated from Penicillium nalgiovense and is identical to the paf gene from P. chrysogenum and encodes a protein with transient antifungal activity (8). All these antifungal proteins are secreted and inhibit the growth of numerous filamentous fungi without affecting bacteria and yeast. Most notably, they are significantly similar in regard to their structures, sizes, and basic characters. The PAF protein exhibits 42.6% sequence similarity with the AFP sequence (18).Not much is known about the modes of action of the antifungal proteins secreted by fungi. It has, however, been shown that defensins, a class of antimicrobial proteins which are quite similar to antifungal proteins in terms of their structures, sizes, and disulfide bridges, interact with anionic phospholipids of bacterial membranes (15). In addition, it has been found that some plant defensins have a receptor-mediated interaction with the fungal plasma membrane (27). However, noth...

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Section: Discussionmentioning

confidence: 85%

The Antifungal Protein from Aspergillus giganteus Causes Membrane Permeabilization

Theis

Wedde

Meyer

et al. 2003

Antimicrob Agents Chemother

104

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“…Our results clearly indicate Thi2.4 acts as an antifungal peptide. α-thionin is known to bind to polysaccharides containing chitin and β-1,3-glucan [37], which are both present in the cell walls of most fungi. Oita et al suggested that α-thionin might bind to chitin and β-1,3-glucan in the cell wall and then be transported to the membrane [37].…”

Section: Discussionmentioning

confidence: 99%

The Secreted Antifungal Protein Thionin 2.4 in Arabidopsis thaliana Suppresses the Toxicity of a Fungal Fruit Body Lectin from Fusarium graminearum

et al. 2013

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Plants possess active defense systems and can protect themselves from pathogenic invasion by secretion of a variety of small antimicrobial or antifungal proteins such as thionins. The antibacterial and antifungal properties of thionins are derived from their ability to induce open pore formation on cell membranes of phytopathogens, resulting in release of potassium and calcium ions from the cell. Wheat thionin also accumulates in the cell walls of Fusarium-inoculated plants, suggesting that it may have a role in blocking pathogen infection at the plant cell walls. Here we developed an anti-thionin 2.4 (Thi2.4) antibody and used it to show that Thi2.4 is localized in the cell walls of Arabidopsis and cell membranes of F. graminearum, when flowers are inoculated with F. graminearum. The Thi2.4 protein had an antifungal effect on F. graminearum. Next, we purified the Thi2.4 protein, conjugated it with glutathione-S-transferase (GST) and coupled the proteins to an NHS-activated column. Total protein from F. graminearum was applied to GST-Thi2.4 or Thi2.4-binding columns, and the fungal fruit body lectin (FFBL) of F. graminearum was identified as a Thi2.4-interacting protein. This interaction was confirmed by a yeast two-hybrid analysis. To investigate the biological function of FFBL, we infiltrated the lectin into Arabidopsis leaves and observed that it induced cell death in the leaves. Application of FFBL at the same time as inoculation with F. graminearum significantly enhanced the virulence of the pathogen. By contrast, FFBL-induced host cell death was effectively suppressed in transgenic plants that overexpressed Thi2.4. We found that a 15 kD Thi2.4 protein was specifically expressed in flowers and flower buds and suggest that it acts not only as an antifungal peptide, but also as a suppressor of the FFBL toxicity. Secreted thionin proteins are involved in this dual defense mechanism against pathogen invasion at the plant-pathogen interface.

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“…Barley and wheat α-thionins are antimicrobial peptides that bind to polysaccharides containing chitin and β-1,3-glucan which compose fungal cell walls (Oita et al 2000). Three 6-kDa antifungalγ-thionins from yellow mustard (Sinapsis alba L.) seeds serve as substrates for plant calcium-dependent protein kinase (Neumann et al 1996).…”

Section: Thioninsmentioning

confidence: 99%

Plant antifungal proteins and their applications in agriculture

Yan

Yuan

Jiang

et al. 2015

Appl Microbiol Biotechnol

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Fungi are far more complex organisms than viruses or bacteria and can develop numerous diseases in plants that cause loss of a substantial portion of the crop every year. Plants have developed various mechanisms to defend themselves against these fungi which include the production of low-molecular-weight secondary metabolites and proteins and peptides with antifungal activity. In this review, families of plant antifungal proteins (AFPs) including defensins, lectins, and several others will be summarized. Moreover, the application of AFPs in agriculture will also be analyzed.

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Binding of Barley and Wheat α-Thionins to Polysaccharides

Cited by 23 publications

References 23 publications

The Antifungal Protein from Aspergillus giganteus Causes Membrane Permeabilization

The Antifungal Protein from Aspergillus giganteus Causes Membrane Permeabilization

The Secreted Antifungal Protein Thionin 2.4 in Arabidopsis thaliana Suppresses the Toxicity of a Fungal Fruit Body Lectin from Fusarium graminearum

Plant antifungal proteins and their applications in agriculture

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