Bacterial rhamnolipids and their 3-hydroxyalkanoate precursors activate Arabidopsis innate immunity through two independent mechanisms

Significance Activation of plant innate immunity relies on the perception of microorganisms through elicitors. Rhamnolipids and their precursor HAAs are exoproducts produced by bacteria. They are involved in bacterial surface dissemination and biofilm development. As these compounds are released in the extracellular milieu, they have the potential to be perceived by the plant immune system. Our work shows that both compounds independently activate plant immunity. We demonstrate that HAAs are perceived by the receptor protein kinase LORE. By contrast, rhamnolipids are not sensed by LORE but activate a noncanonical immune response influenced by the sphingolipid composition of the plant plasma membrane. Thus, plants can sense bacterial molecules as well as their direct precursors to trigger distinct immune responses.