Résumé
Ralstonia solanacearum is a soil-born plant pathogen responsible of the lethal bacterial wiltdisease on more than 250 plant species. This bacterium is characterized by a strong adaptivecapacity, no effective control method is available today and new strains able to colonize newhosts are continuously emerging. Many works investigated in a better understanding of theadaptive processes in R. solanacearum and demonstrated the importance of genomicpolymorphisms. However, the contribution of epigenetic modifications in R. solanacearumadaptation has still not been studied. Here, we used SMRT sequencing to investigatemodifications in adenine methylation (6mA) profile in experimentally evolved clones. Theseclones derived from the GMI1000 strain after experimental evolution during 300 generationsin a fixed plant line. Most of the evolved clones showed a better fitness in their experimentalhost than the ancestral clone and contained between 0 and 9 genomic polymorphisms.Methylome analysis of 35 clones evolved in 5 different plant species detected 58 differentialmethylation regions (DMRs) including 54 differential hemimethylations and 4 (2x2)differential methylations. These last 4 DMRs concerned two motifs in the upstream region ofa gene (named gene R) and were validated by MSRE-qPCR (Methylation Sensitive RestrictionEnzyme – quantitative PCR). Using site-directed mutagenesis of the two methylated motifsand competition experiments in plants between the mutant and the evolved clone, wedemonstrated that methylation of the two motifs in the upstream region of gene R gives anadaptive advantage to R. solanacearum during growth in planta.