The ubiquitin/proteasome system in plant-pathogen interaction

Abstract

Ubiquitin (Ub) is a small protein used to label proteins by eukaryotic organisms; in most cases labeled proteins will be degraded afterwards. Ubiquitination occurs in three sequential steps through reactions requiring the action of the ubiquitin-activating enzyme, the ubiquitin-conjugating enzyme and the ubiquitin ligase. After this, the target protein will follow a different fate according to ubiquitination topology. Most ubiquitinated proteins will be degraded in the 2.5 M protein complex termed the 26S proteasome. Plants employ this mechanism of regulated protein degradation to modulate developmental and growing processes as well as to respond to detrimental situations, like water deficit or pathogen attack. During the evolution plants have developed different strategies to cope against pathogen infection, however these organisms have acquired tools that allow them to counteract plant defense mechanisms. Among different ways to undermine plant resistance pathways, pathogens have now the ability to manipulate the Ub/proteasome system to efficiently infect them.