Manipulation of ABA Content in Modifies Sensitivity and Oxidative Stress Response to and Influences Peroxidase Activity.

The production of reactive oxygen species (ROS) is one of the first defense reactions induced in in response to infection by the pectinolytic enterobacterium . Previous results also suggest that abscisic acid (ABA) favors multiplication and spread into its hosts. Here, we confirm this hypothesis using ABA-deficient and ABA-overproducer plants. We investigated the relationships between ABA status and ROS production in after infection and showed that ABA status modulates the capacity of the plant to produce ROS in response to infection by decreasing the production of class III peroxidases. This mechanism takes place independently of the well-described oxidative stress related to the RBOHD NADPH oxidase. In addition to this weakening of plant defense, ABA content in the plant correlates positively with the production of some bacterial virulence factors during the first stages of infection. Both processes should enhance disease progression in presence of high ABA content. Given that infection increases transcript abundance for the ABA biosynthesis genes and and triggers ABA accumulation in leaves, we propose that manipulates ABA homeostasis as part of its virulence strategy.