Chlorosis-inducing products from Pseudomonas syringae pathovars: New N-coronafacoyl compounds

Liquid cultures of Pseudomonas syringae pv. tomato strains that also produc ed the phytotoxin coronatine, were found to have a new chlorosis-inducing a ctivity, not previously described. Bioassay-guided fractionation and HPLC a nalysis revealed two new peaks that were chlorosis-inducing on leaves of be an plants. Mass spectrometry and NMR analyses of the compounds led to the d erivation of their structures as coronafacoyl-L-serine and coronafacoyl-L-t hreonine, respectively. The amino acid C-2 configurations were determined b y GC analysis following hydrolysis with 6M KCI. Both compounds have more po lar and more acidic properties than coronatine, norcoronatine, and other kn own coronafacoyl conjugates with non-polar amino acids. Investigation of Ps eudomonas syringae pv. glycinea:strains that are known to be prolific produ cers of the coronatine family of compounds revealed the production of coron afacoylserine and coronafacoylthreonine also. (C) 1998 Published by Elsevie r Science Ltd. All rights reserved.