The bacterium Xanthomonas campestris pv. campestris (Xcc) causes black rot disease in Brassica crops. Glucosinolates are known to be part of the defence system of Brassica crops against Xcc infection. They are activated upon pathogen attack by myrosinase enzymes. Their hydrolytic products (GHPs) inhibit the growth of Xcc in vitro. However, the mechanisms underlying this inhibition and the way Xcc can overcome it are not well understood. We studied the transcriptomic reprogramming of Xcc after being supplemented with two chemically different GHPs, one aliphatic isothiocyanate (allyl-ITC) and one indole (indol-3-carbinol), by RNA-seq. Based on our results, the arrest in Xcc growth is related to the need to stop cell division to repair damaged DNA and cell envelope components. Otherwise, GHPs modify energy metabolism by inhibiting aerobic respiration and increasing the synthesis of glycogen. Xcc induces detoxification mechanisms such as the antioxidant defence system and the multidrug efflux system to cope with the toxic effects driven by GHPs. This is the first time that the transcriptomic reprogramming of a plant pathogenic bacterium treated with GHPs has been studied. This information will allow a better understanding of the interaction of a plant pathogen mediated by GSLs.
Keywords: Brassicaceae; black rot; isothiocyanate; plant secondary metabolites; plant–pathogen interaction.