Lipid transfer proteins (nsLTPs) from barley and maize leaves are potent inhibitors of bacterial and fungal plant pathogens
Abstract
Four homogeneous proteins (Cw18, Cw20, Cw21, Cw22) were isolated from etiolated barley leaves by extraction of the insoluble pellet from a Tris-HCl (pH 7.5) homogenate with 1.5 M LiCl and fractionation by reverse-phase high-performance liquid chromatography. All 4 proteins inhibited growth of the pathogen Clavibacter michiganensis subsp. sepedonicus (EC50s = 1-3 x 10(-7) M) and had closely related N-terminal amino acid sequences. The complete amino acid sequences of proteins Cw18 and Cw21 were determined and found to be homologous to previously described, non-specific lipid transfer proteins from plants (32-62% identical positions). The proteins also inhibited growth of the bacterial pathogen Pseudomonas solanacearum (EC50s = 3-6 x 10(-7) M) and the fungus Fusarium solani (EC50s = 3-20 x 10(-6) M). A homologous protein from maize leaves (Cw41) was purified in a similar manner and also found to have inhibitory properties. A synergistic effect against the fungus was observed when protein Cw21 was combined with thionins. A defense role for non-specific lipid transfer proteins from plants is proposed.