The Ubiquitination System in Plants

Most of the plant growth and development are regulated by the ubiquitin-proteasome pathway.The ubiquitin-proteasome pathway(UPP) consists of two major components: the ubiquitination system attaching a ubiquitin or a polyubiquitin chain to a substrate,and the 26S proteasome responsible for the degradation of protein substrates tagged by the polyubiquitin chain.Ubiquitin attachment is a multistep reaction involving three enzymes referred to as E1(ubiquitin-activating enzyme),E2(ubiquitin-conjugating enzyme),and E3(ubiquitin-protein ligase).Their known biological functions include photomorphogenesis,gametogenesis,floral development,seed development,hormone signaling,responses to biotic and abiotic challenges.