Abstract
The bacterial pathogen Acidovorax citrulli causes the destructive fruit blotch (BFB) on cucurbit plants. Pseudomonas chlororaphis YL-1 is a bacterial strain isolated from Mississippi soil and its genome harbors some antimicrobial-related gene clusters, such as phenazine, pyrrolnitrin, and pyoverdine. Here, we evaluated the antimicrobial activity of strain YL-1 as compared with its deficient mutants of antimicrobial-related genes, which were obtained using a sacB-based site-specific mutagenesis strategy. We found that only phenazine-deficient mutants ΔphzE and ΔphzF almost lost the inhibitory effects against A. citrulli in LB plates compared with the wild-type strain YL-1, and that the main antibacterial compound produced by strain YL-1 in LB medium was phenazine-1-carboxylic acid (PCA) based on the liquid chromatography-mass spectrometry (LC-MS) analysis. Gene expression analyses revealed that PCA enhanced the accumulation of reactive oxygen species (ROS) and increased the activity of catalase (CAT) in A. citrulli. The inhibition effect of PCA against A. citrulli was lowered by adding exogenous CAT. PCA significantly upregulated the transcript level of katB from 6 to 10 h, which encodes CAT that helps to protect the bacteria against oxidative stress. Collectively, the findings of this research suggest PCA is one of the key antimicrobial metabolites of bacterial strain YL-1, a promising biocontrol agent for disease management of BFB of cucurbit plants.
Highlights
Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, is a destructive disease that infects cucurbit plants [1]
Indicates the production of hydrogen cyanide (Figure S3). These results showed that the sacB-mediated genetic manipulation system used for P. chlororaphis YL-1 was stable and efficient
The enzyme involved in phenazine biosynthesis is a typeisIIa3-deoxy-D-arabinoheptulosonate-7first enzyme involved in phenazine biosynthesis type II 3-deoxy-D-arabinoheptuphosphate (DAHP)
Summary
Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, is a destructive disease that infects cucurbit plants [1]. The disease was first found in Florida in the USA in 1989 [2]. The disease has been involuntarily spread to many parts of the world by contaminated commercial seeds [1]. It was reported that seeds even with a low level of A. citrulli containment can result in severe BFB epidemics under a favorable environment [3]. A. citrulli causes leaf blight, seedling blight, and/or blossom rot of cucurbitaceous plants. Annual yield loss of watermelon caused by BFB in the USA reached
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
