An investigation into the proteolytic degradation of antimicrobial peptides by plant extracts and localisation of pleurocidin in transgenic saccharum hybrid species.

Abstract

Two cationic antimicrobial peptides, ESF I-GR7, and pleurocidin, were assessed for their stability in plant intercellular fluid, the targeted locale for their expression in transgenic plants. Incubation of ESFI-GR7 and pleurocidin with intercellular fluid (ICF) extracted from sugarcane, tomato and tobacco leaves reduced their biotoxicity towards various pathogens, namely Camobacterium mobile DMSO and Xanthomollas campestris. It was concluded that it may be necessary to modify the aminoacid structures of the peptides in order to ensure that endogenous proteases would not degrade the peptides once expressed in a transgenic environment. The presence of pleurocidin was detected in transgenic sugarcane transformed (in a previous study) with pleurocidin gene cloned into the pUBI 510 plasmid. ICF was extracted from four month old transgenic Saccharum hybrid species (sugarcane). Western blotting verified the presence of the transgenic protein in crude protein extracts. Immunogold labelling and transmission electron microscopy were performed to investigate the localisation of transgenic pleurocidin. The peptide was localized predominantly in the intercellular spaces and cell wall sugarcane leaves.