A novel cysteine-rich antifungal peptide ToAMP4 from Taraxacum officinale Wigg. flowers

A novel peptide named ToAMP4 was isolated from Taraxacum officinale Wigg. flowers by a combination of acetic acid extraction and different types of chromatography: affinity, size-exclusion, and RP-HPLC. The amino acid sequence of ToAMP4 was determined by automated Edman degradation. The peptide is basic, consists of 41 amino acids, and incorporates three disulphide bonds. Due to the unusual cysteine spacing pattern, ToAMP4 does not belong to any known plant AMP family, but classifies together with two other antimicrobial peptides ToAMP1 and ToAMP2 previously isolated from the dandelion flowers. To study the biological activity of ToAMP4, it was successfully produced in a prokaryotic expression system as a fusion protein with thioredoxin. The recombinant peptide was shown to be identical to the native ToAMP4 by chromatographic behavior, molecular mass, and N-terminal amino acid sequence. The peptide displays broad-spectrum antifungal activity against important phytopathogens. Two ToAMP4-mediated inhibition strategies depending on the fungus were demonstrated. The results obtained add to our knowledge on the structural and functional diversity of AMPs in plants.