THE ACTIVITY OF LIPID-A AND CORE COMPONENTS OF BACTERIAL LIPOPOLYSACCHARIDES IN THE PREVENTION OF THE HYPERSENSITIVE RESPONSE IN PEPPER

Pre-treatment of leaves of pepper (Capsicum annuum) with lipopolysacch aride (LPS) preparations from enteric bacteria and Xanthomonas campest ris could prevent the hypersensitive response caused by an avirulent X . campestris strain, By use of a range of deep-rough mutants, the mini mal structure in Salmonella LPS responsible for the elicitation of thi s effect was determined to be lipid A attached to a disaccharide of 2- keto-3-deoxyoctulosonate; lipid A alone and the free core oligosacchar ide from a Salmonella Ra mutant were not effective, For Xanthomonas, t he core oligosaccharide alone had activity although lipid A was not ef fective, The results suggest that pepper cells can recognize different structures within bacterial LPS to trigger alterations in plant respo nse to avirulent pathogens.