Repeated gain and loss of a single gene modulates the evolution of vascular plant pathogen lifestyles (Science Advances)

Within the bacterial genus Xanthomonas there are many plant pathogens, some of which colonize living cells within leaves, and others of which are vascular pathogens that colonize and spread through vascular tissues. Gluck-Thaler et al. looked at genomes from sets of closely related bacteria that are either vascular or nonvascular plant pathogens. They identified a gene, cbsA, encoding a cell wall–degrading cellobiohydrolase that is found in almost all vascular pathovars and absent from the nonvascular ones. Remarkably, heterologous expression of cbsA bestows vascular pathogenesis to a nonvascular pathogen. Further analysis indicates that the presence of cbsA is ancestral, that it has been repeatedly lost in nonvascular pathovars, and also that it has been regained in some pathovars through horizontal gene transfer. In other words, “the repeated gain and loss of a single gene can act as a phenotypic switch.” (Summary by Mary Williams @PlantTeaching) Science Advances 10.1126/sciadv.abc4516