Proteomic Analysis of a Leaf Spot Pathogen, Xanthomonas euvesicatoria pv. euvesicatoria 173 upon Sublethal Dose of Cinnamon Essential Oil

Cinnamon essential oil (CEO) exhibits antimicrobial activity in a dose-dependent manner, offering potential for controlling plant bacterial diseases. This study investigated the effects of CEO on Xanthomonas euvesicatoria pv. euvesicatoria 173, the causal agent of pepper bacterial spot disease. Treatment with an EC50 dose of CEO significantly altered bacterial culturability and protein expression profiles. Proteomic analyses revealed that, relative to untreated control, a TonB-dependent receptor and a Clp protease were upregulated, and ATP-binding cassette transporter proteins were downregulated in the CEO-exposed X. euvesicatoria. Quantitative real-time PCR confirmed that TonB and Clp proteases abundance positively correlated with transcriptional upregulation of their corresponding genes. Our findings suggest that CEO disrupts cellular homeostasis by targeting key membrane functions. Further investigation is required to elucidate how key changes in transport and proteolytic systems contribute to the control by CEO of the plant pathogen, X. euvesicatoria.