Ralstonins A and B, Lipopeptides with Chlamydospore-Inducing and Phytotoxic Activities from the Plant Pathogen Ralstonia solanacearum

Ralstonia solanacearum has an orphan hybrid polyketide synthase-nonribosomal peptide synthetase gene cluster. We herein isolate its products (named ralstonins A and B) from R. solanacearum and elucidate their structures and biological activities. Ralstonins are unusual lipodepsipeptides composed of 11 amino acids (containing unique amino acids such as β-hydroxytyrosine and dehydroalanine) and a 3-amino-2-hydroxyoctadecanoic acid, and their production is controlled by quorum sensing, a mechanism of bacterial cell-cell communication. Ralstonins exhibited chlamydospore-inducing activity and phytotoxicity.