Professor MAP UMR5240 INSA LYON Villeurbanne, Rhone-Alpes, France
Dickeya is a genus of plant-pathogenic enterobacteria that cause soft rot diseases in many economically important crops. The infection progresses from an asymptomatic to a symptomatic phase, during which enzymes are secreted to macerate plant tissues. Throughout this process, D. dadantii must tightly regulate its virulence factors in response to changing environmental conditions. Our research uncovers a novel layer of regulation involving RNAs. We discovered that the transcript of pecS, a transcriptional repressor of virulence genes, overlaps with the mRNA of the neighboring argG gene. Given that argG is expressed in the absence of arginine, and PecS suppresses virulence, we hypothesized that arginine levels could influence bacterial pathogenicity. Our findings reveal that PecS levels significantly increase in the presence of arginine and upon argG overexpression. When the genomic arrangement is disrupted, argG overexpression no longer impacts PecS levels suggesting that gene organization plays a crucial role in this regulatory mechanism. Moreover, virulence factor expression increases significantly in arginine-deprived conditions highlighting a direct link between bacterial metabolism and virulence. We propose that pecS and argG may regulate each other via direct mRNA-mRNA interactions connecting bacterial metabolic activity and pathogenicity. In planta experiments are ongoing to assess the effect of apoplastic arginine on the infection process of D. dadantii.
