Cell wall DAMPs (damage-associated molecular patterns) and their oxidation in the Arabidopsis seed coat development and grafting

Plants immunity can be triggered by endogenous elicitors, the DAMPs. DAMPs like oligogalacturonides (OGs) from homogalacturonan and cellodextrins (CDs) from cellulose. OGs and CDs are inactivated by oxidases, OGOX1-4 and CELLOX1. My thesis consists of two parts. The first deals with the identification of a new member of the BBE-like family in Arabidopsis thaliana, At5g44360/BBE23 (CELLOX2). I determined its biochemical characteristics. The activity of CELLOX2 is similar to CELLOX1. The DAMPs mixed-linked β-1,3/1,4-glucans have been uncovered as new substrates for CELLOX1 and CELLOX2. I also investigated the physiology of these enzymes in the seed. The second part concerned the role of OGs and CDs and their oxidases during the grafting. The molecular mechanisms of grafting remain unknown. Its elucidation includes the study of the wound, tissue regeneration, vascular reconnection, and interactions with hormones. OGOX1 and CELLOX1 genes are differentially expressed at the graft junction. I found that CDs, like OGs, inhibit auxin responses. The auxin-regulated DR5::GUS expression shows a positive effect on the response to CDs in the meristems. So OGs and CDs influence grafting, at the level of the vascular tissue formation and differentiation. These results may lead to an optimization of grafting and vascular development.