ANALYSIS OF THE TOXICITY OF PUROTHIONINS AND HORDOTHIONINS FOR PLANT-PATHOGENIC BACTERIA

Purothionins (PTHs) and hordothionins (HTHs) were purified by cation-e xchange chromatography from petroleum-ether extracts of wheat and barl ey flour respectively. The HTHs could be separated into two fractions, HTH-1 and HTH-2. Radial diffusion assays and micro-plate broth diluti on assays with a number of plant pathogenic bacteria showed that these proteins were toxic for Clavibacter michigancnsis subsp. michiganensi s, the causal agent of bacterial canker on tomato, C. m. subsp. sepedo nicus, the causal agent of ring rot on potato, and Xanthomonas campest ris pv. vesicatoria, the causal agent of a spot disease on tomato and pepper. Only minor differences in toxicity between PTHs and HTHs, and between HTH-1 and HITH-2, were detected. Minor differences in toxicity of these thionins were also detected for different strains of these b acteria. The use of these plant proteins for engineering bacterial dis ease resistance into solanaceous crops will be discussed.