Purification And Characterization Of Antimicrobial Peptides From The Seeds Of Capsella Bursapastoris L.Medic And Cheiranthus Cheiri L.

Antimicrobial peptidesare low-molecular-weight peptides produced by a diversity of organisms,which can inhibit or kill pathogenic microorganisms.They have many advantages such as possession of a low molecular weight,complex structure,temperature stability and pH stability,wide antimicrobial spectrum and low antimicrobial resistance.These advantages make antimicrobial peptides promising candidates for application in the fields of peptide antibiotics and plant gene engineering.In this study,seeds of Capsella bursapastoris L.Medic and Cheiranthus cheiri L.were selected as experimental materials from 45 kinds of plant seeds.SP-Sepharose,Mono STM 5/50GL and SuperdexTM 75 10/300GL are used successively to purify antimicrobial peptides.The purified peptides are named ASU2 and BSU3,respectively.The results of Tricine-SDS-PAGE show that the molecular weights of ASU2 and BSU3 are about 10 kDa and about 8 kDa,respectively.The analysis of peptide by AB SCIEX 4700 TOF/TOF shows that ASU2 has high homology with hypothetical protein from Eutrema salsugineum and BSU3 has high homology with serum albumin from Bubalus bubalis.Assay of antimicrobial activity shows that the antifungal activity of ASU2 and BSU3 havepronounced thermal and pH stability and are highly resistant to cations,organic solvents and surfactant.The inhibition ratio against phytopathogen have been determined.The result disclose that IC50values of of ASU2 and BSU3 are 4.32?g/mLtoward Fusarium solanif.sp.glycinesand 1.93 ?g/mLtoward Fusarium oxysporum,respectively.The fluorescent dye experiment showed ASU2 and BSU3 can induce chitin deposits at hyphal tips.They can also permeabilize the hyphal membrane.Hence the mechanism of antifungal action of ASU2 and BSU3 entail hyphalmembranepermeabilization and chitin deposits at hyphal tips.Other mechanisms,if any,await elucidation.