Fabrication of Isopropanolamine-Decorated Coumarin Derivatives as Novel Quorum Sensing Inhibitors to Suppress Plant Bacterial Disease

Abstract

Emerging pesticide-resistant phytopathogenic bacteria have become a stumbling block in the development and use of pesticides. Quorum sensing (QS) blockers, which interfere with bacterial virulence gene expression, are a compelling way to manage plant bacterial disease without resistance. Herein, a series of isopropanolamine-decorated coumarin derivatives were designed and synthesized, and their potency in interfering with QS was investigated. Notably, compound <b>A</b>_<b>5</b> exhibited a better bioactivity with median effective concentration (EC₅₀) values of 6.75 mg L^-1 against <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> (<i>Xoo</i>) than bismerthiazol (EC₅₀ = 21.9 mg L^-1). Further biochemical studies revealed that compound <b>A</b>_<b>5</b> disturbed biofilm formation and suppressed bacterial virulence factors and so forth. Moreover, compound <b>A</b>_<b>5</b> decreased the expression of QS-related genes. Interestingly, compound <b>A</b>_<b>5</b> had the acceptable control effect (53.2%) toward <i>Xoo</i> <i>in vivo</i>. Overall, this study identifies a novel lead compound for the development of bactericide candidates to control plant bacterial diseases by interfering with QS.