Ubiquitination plays important roles in plant adapting itself to internal and external signals to regulate plant growth and development.The model plant Arabidopsis (Arabidopsis thaliana) genome size is about 120 Mbs and it contains near 30,000 predicted genes, in which approximately 5% of the Arabidopsis proteome is predicted to be involved in the ubiquitination/26S proteasome pathway.Recent developments in plant stress biology have demonstrated that numbers of plant E3 complexes involved in both biotic and abiotic stress signaling.