Lipid transfer proteins (nsLTPs) from barley and maize leaves are potent inhibitors of bacterial and fungal plant pathogens

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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 × 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 × 10−7 M) and the fungus Furium solani (EC50s = 3–20 × 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.