Reversible posttranslational modification of proteins by the action of small ubiquitin-like modifier (SUMO) peptide (sumoylation) has been known to participate in various biological processes in eukaryotes. However, much less is known about the role of sumoylation in plants. In our recent paper to which we write this Addendum, we show that loss of SIZ1, a SUMO E3 ligase, results in a highly increased SA-mediated defense signaling through a PAD4-dependent pathway. This signaling leads to constitutively expressed pathogen related (PR) genes and to increased disease resistance to a virulent bacterial pathogen. These findings significantly increase our understanding of the role of sumoylation in the plant defense system.
Keywords: plant innate immunity; plant-pathogen interactions; salicylic acid (SA); small ubiquitin-like modifer (SUMO).