Department of Plant Pathology and Microbiology, National Taiwan University, Taipei 10617, Taiwan, R.O.C.
LsGRP1 is a defense-related gene differentially expressed in lily leaves in response to pathogen attack. The difficulty in the expression of LsGRP1 in Escherichia coli suggested the presence of antimicrobial activity in LsGRP1. To evaluate the antimicrobial trait of LsGRP1, three LsGRP1-derived peptides were chemically synthesized; namely LsGRP1N (N-terminal region without the signal peptide), LsGRP1G (glycine-rich region), and LsGRP1C (C-terminal cysteine-rich region). LsGRP1C was proposed to be a potential antimicrobial agent according to its broad-spectrum and effective antimicrobial activity. LsGRP1C displayed inhibition effects on bacterial and fungal growth, possibly by altering the integrity of the cell membrane, as indicated by scanning electron microscopy and SYTOX Green staining assays. Additionally, LsGRP1C induced programmed cell death-like phenomenon in the tested fungal species as indicated by 2′,7′-dichlorodihydrofluorescein diacetate and 4′,6′-diamidino-2-phenylindole assays. Further immunofluorescence staining showed that LsGRP1C was located at the fungal cell surface. According to these observations, we concluded that LsGRP1C originated from the plant defense-related protein LsGRP1 would play a role as an antimicrobial peptide and have a potential for practical use.