In the last decade, SUMOylation has emerged as an essential post-translational 
modification in eukaryotes. In plants, the biological role of SUMO (small 
ubiquitin-related modifier) has been studied through genetic approaches that 
together with recent biochemical studies suggest that the plant SUMOylation 
system has a high degree of complexity. The present review summarizes our 
current knowledge on the SUMOylation system in Arabidopsis, focusing on the 
mechanistic properties of the machinery components identified.