Abstract: The ubiquitin/26S proteosome pathway mainly consists of ubiquitin activating enzyme (E1),ubiquitin conjugating enzyme (E2), ubiquitin protein ligase (E3), and 26S proteasome. In the initial reaction, E1 activates the Ub by coupling ATP hydrolysis, the activated Ub is then transferred to an E2. The E2 either transfers ubiquitin directly to the E3 in the case of HECT E3s or binds the E3 and transfers the ubiquitin to the substrate. Polyubiquinated proteins are eventually degraded by the 26S proteasome. In plants, regulated protein degradation by the ubiquitin/26S proteosome contributes significantly to development by affecting a wide range of processes, including hormone signaling, photomorphogenesis, and flower development.