Transcriptome alteration in Phytophthora infestans in response to phenazine-1-carboxylic acid production by Pseudomonas fluorescens LBUM223
Martin Filion: Université de Moncton
<div><em>Phytophthora infestans</em> is responsible for late blight, one of the most devastating potato diseases. Phenazine-1-carboxylic acid (PCA)-producing <em>Pseudomonas fluorescens</em> LBUM223 shows biocontrol potential against various plant pathogens, including <em>P. infestans</em>. We wished to further characterize the effect of PCA-producing LBUM223 on the transcriptome of <em>P. infestans </em>using an <em>in vitro</em> time-course confrontational study with <em>P. infestans</em> inoculated alone (control) or with wild-type LBUM223, its isogenic mutant (no PCA production), or synthetic PCA. Destructive sampling was performed at 6, 9 and 12 days, the transcriptome was analysed using RNA-Seq and the expression of a subset of differentially expressed genes was validated by RT-qPCR. Both LBUM223 and synthetic PCA significantly repressed <em>P. infestans’</em> growth at all times. Compared to the control treatment, transcriptomic analyses showed that the percentage of genes significantly altered by LBUM223 and synthetic PCA increased as time progressed, up to 61% and 46%, respectively. When all time points were combined, PCA, either synthetic or produced by LBUM223, led to 214 differentially expressed genes. These key genes are involved in major cell functions, like oxidoreduction activity and phosphorylation mechanisms. Interestingly, even though no host plant tissue was present in the <em>in vitro</em> system, PCA also led to the overexpression of several genes encoding effectors, suggesting an implication in biocontrol.</div>
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