The diverse roles of ubiquitin and the 26s proteasome in the life of plants

KEY POINTS * The tagging of proteins with ubiquitin and their subsequent degradation by the 26S proteasome provides a highly regulated proteolysis system that is necessary in all eukaryotes.

* The ubiquitylation of a target protein involves the sequential action of E1, E2 and E3 enzymes; E3 ubiquitin ligase provides target specificity. * Plants use ubiquitin and the 26S

proteasome to control a wide variety of developmental processes through the degradation of key cellular regulators. * Approximately 5% of the _Arabidopsis thaliana_ genome encodes components

of the ubiquitin/26S proteasome system. * We discuss the roles of ubiquitin in the regulation of floral development, responses to plant hormones and to pathogens, and in the regulation of

photomorphogenesis. * The COP9 signalosome (CSN) is intimately connected to the ubiquitin/26S proteasome system and might regulate the activity of SCF-type (and possibly other) E3 ligases. *

Recent advances, particularly in the fields of hormone signalling and responses to pathogens, have shown just how frequently plants use ubiquitin to regulate cellular processes and indicate

that ubiquitin and the 26S proteasome act as regulators in many more, as yet unidentified, plant developmental processes. ABSTRACT A tightly regulated and highly specific system for the

degradation of individual proteins is essential for the survival of all organisms. In eukaryotes, this is achieved by the tagging of proteins with ubiquitin and their subsequent recognition

and degradation by the 26S proteasome. In plants, genetic analysis has identified many genes that regulate developmental pathways. Subsequent analysis of these genes has implicated ubiquitin

and the 26S proteasome in the control of diverse developmental processes, and indicates that proteolysis is a crucial regulatory step throughout the life cycle of plants. Access through

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CONTENT BEING VIEWED BY OTHERS THE RPN12A PROTEASOME SUBUNIT IS ESSENTIAL FOR THE MULTIPLE HORMONAL HOMEOSTASIS CONTROLLING THE PROGRESSION OF LEAF SENESCENCE Article Open access 30

September 2022 CUL3 E3 LIGASES IN PLANT DEVELOPMENT AND ENVIRONMENTAL RESPONSE Article 15 January 2021 MECHANISMS CONTROLLING PLANT PROTEASES AND THEIR SUBSTRATES Article 08 February 2023

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interaction of SCF ubiquitin E3 ligase subunits from _Arabidopsis_. _Plant J._ 34, 753–767 (2003). CAS  PubMed  Google Scholar  Download references ACKNOWLEDGEMENTS J.A.S. is supported by a

Human Frontiers Science Program long-term fellowship. Research in K.S.'s laboratory is supported in part by grants from the Gatsby Charitable Foundation and the Biotechnology and

Biological Sciences Research Council. Related research in X.W.D.'s laboratory is supported by grants from the National Institutes of Health and the National Science Foundation. AUTHOR

INFORMATION AUTHORS AND AFFILIATIONS * Deptartment of Molecular, Cellular and Developmental Biology, Yale University, PO Box 208104, 165 Prospect Street, New Haven, 06520-8104, Connecticut,

USA James A. Sullivan & Xing Wang Deng * The Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich, NR4 7UH, UK Ken Shirasu Authors * James A. Sullivan View author publications

You can also search for this author inPubMed Google Scholar * Ken Shirasu View author publications You can also search for this author inPubMed Google Scholar * Xing Wang Deng View author

publications You can also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to Xing Wang Deng. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare

that they have no competing financial interests. RELATED LINKS RELATED LINKS DATABASES TAIR _APETALA3_ _Axr1_ _CIO1_ _COP_ _COP10_ _DET_ _FUS_ _LEAFY_ _NIM1_ _PISTILLATA_ _RAR1_ _RGA_

_SGT1α_ _SGT1b_ _SKP1_ _SLEEPY1_ ubiquitin _UNUSUAL FLORAL ORGANS_ _UPL3_ UK CROPNET _Mla6_ _Mla12_ FURTHER INFORMATION Xing Wang Deng's laboratory GLOSSARY * PROTO-ONCOGENE A gene that

has the potential to change into an active cancer-causing oncogene. * ENDOCYTOSIS The uptake of extracellular materials within membrane-bound vesicles by cells. * ISOPEPTIDE BOND The

covalent linkage that joins amino-acid residues through an amide bond. * THIOESTER LINKAGE A non-covalent chemical bond between two proteins formed through thiolester. * CONJUGATION The

addition of ubiquitin moieties to a growing polyubiquitin chain. * SENESCENCE Regulated death of an organ or a cell after its normal physiological function. * CHELATION The process by which

an organic chemical bonds with metal ions and thereby removes them from solutions. * WHORLS A specific layer of flower organs that is generated through floral meristem activity. * SEPALS The

protective outer layer of flower. * STAMENS The third layer of flower that bears the male gametophyte that produces pollen. * CARPELS The fourth whorl of flower that bears the female

gametophyte. * TRANSFORMATION The change from one developmental pattern to another. * APICAL DOMINANCE Concentration of growth at the tip of a plant shoot, where a terminal bud exerts

partial inhibition of auxiliary bud growth. * ALEURONE CELLS A cell type in cereal kernals that undergoes highly regulated cell death to release stores of minerals and nutrients to the

developing embryo. * PHENOCOPY The production of a phenotype, which closely resembles a phenotype that normally results from specific gene expression or from gene mutation. * POWDERY MILDEW

A group of plant diseases that are caused by the growth of fungal mycelium and the production of spores on the surface of plant tissues. * DENEDDYLATION The removal of the ubiquitin-like

modifier NEDD8 (also called RUB) from a protein. * HISTONE DEACETYLASE The enzyme that removes acetyl groups from lysine residues in the DNA-binding histone group of proteins. *

SKOTOMORPHOGENIC Developmental pattern followed by seedlings in the absence of light. * HYPOCOTYLS The stem of a seedling. * COTYLEDONS The leaves of a seedling formed during embryonic

development. * PHOTOMORPHOGENIC Developmental pattern followed by seedlings in the presence of light. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE

Sullivan, J., Shirasu, K. & Deng, X. The diverse roles of ubiquitin and the 26S proteasome in the life of plants. _Nat Rev Genet_ 4, 948–958 (2003). https://doi.org/10.1038/nrg1228

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