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Interaction transcriptomic profiling- enabled insights into the DSF-mediated quorum sensing regulation during Xanthomonas citri infection on citrus

Jinyun Li: University of Florida

<div>The <em>Xanthomonas</em> genus contains a large group of plant pathogens, which cause severe diseases on many crops worldwide. The diffusible signal factor (DSF) - mediated quorum sensing (QS) regulatory system coordinates expression of virulence factors in these pathogens. However, the regulatory effects of this system during the <em>Xanthomonas-</em> plant interactions remain unclear from both the pathogen and host aspects. Here, we investigated the <em>in planta</em> DSF- mediated QS regulon of <em>X. citri</em> subsp<em>. citri</em> (Xac), the causal agent of citrus canker, and the transcriptional responses of citrus to DSF-mediated Xac infection using the dual RNA-seq approach. Comparative transcript profiles of Xac strain 306 and its DSF-deficient (∆rpfF) mutant revealed that DSF- mediated QS specifically modulates bacterial adaptation, nutrition uptake and metabolisms, stress tolerance, virulence, and signal transduction to favor host infection. The transcriptional responses of citrus to DSF-mediated Xac infection are characterized by downregulation of photosynthesis genes and plant defense related genes. Alterations of plant hormone signaling pathways were also triggered by DSF-mediated Xac infection to benefit the pathogen. These findings suggest that the DSF/Rpf QS system modulates the citrus phenotypes to favor Xac infection. Collectively, our results provide new insight into the DSF- mediated QS regulation during plant-pathogen interactions and advance the understanding of traits used by <em>Xanthomonas</em> to adapt to the <em>in planta</em> environments.</div>