Plants utilize the ubiquitin proteasome system (UPS) to orchestrate numerous essential cellular processes, including the rapid responses required to cope with abiotic and biotic stresses. The 26S proteasome serves as the central catalytic component of the UPS that allows for the proteolytic degradation of ubiquitin-conjugated proteins in a highly specific manner. Despite the increasing number of studies employing cell-free degradation assays to dissect the pathways and target substrates of the UPS, the precise extraction methods of highly potent tissues remain unexplored. Here, we utilize a fluorogenic reporting assay using two extraction methods to survey proteasomal activity in different Arabidopsis thaliana tissues. This study provides new insights into the enrichment of activity and varied presence of proteasomes in specific plant tissues.
Trichome development is a fascinating model to elaborate the plant cell differentiation and growth processes. A wealth of information has pointed to the contributions of the components associated with cell cycle control and ubiquitin/26S proteasome system (UPS) to trichome morphogenesis, but how these two pathways are connected remains obscure. Here, we report that HECT‐type ubiquitin ligase KAKTUS (KAK) targets the cyclin‐dependent kinase (CDK) inhibitor KRP2 (for kip‐related protein 2) for proteasome‐dependent degradation during trichome branching in Arabidopsis. We show that over‐expression of
- Award ID(s):
- 2425989
- PAR ID:
- 10442170
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 116
- Issue:
- 3
- ISSN:
- 0960-7412
- Format(s):
- Medium: X Size: p. 871-886
- Size(s):
- p. 871-886
- Sponsoring Org:
- National Science Foundation
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SUMMARY Cell differentiation and morphogenesis are crucial for the establishment of diverse cell types and organs in multicellular organisms. Trichome cells offer an excellent paradigm for dissecting the regulatory mechanisms of plant cell differentiation and morphogenesis due to their unique growth characteristics. Here, we report the isolation of an Arabidopsis mutant,
a berrantlyb ranchedt richome 3–1abt3‐1 ), with a reduced trichome branching phenotype. Positional cloning and molecular complementation experiments confirmed thatabt3‐1 is a new mutant allele ofAuxin resistant 1 (AXR1 ), which encodes the N‐terminal half of ubiquitin‐activating enzyme E1 and functions in auxin signaling pathway. Meanwhile, we found that transgenic plants expressing constitutively active version ofROP2 (CA‐ROP2 ) caused a reduction of trichome branches, resembling that ofabt3‐1 . ROP2 is a member of Rho GTPase of plants (ROP) family, serving as versatile signaling switches involved in a range of cellular and developmental processes. Our genetic and biochemical analyses showedAXR1 genetically interacted withROP2 and mediated ROP2 protein stability. The loss ofAXR1 aggravated the trichome defects ofCA‐ROP2 and induced the accumulation of steady‐state ROP2. Consistently, elevatedAXR1 expression levels suppressedROP2 expression and partially rescued trichome branching defects inCA‐ROP2 plants. Together, our results presented a new mutant allele ofAXR1 , uncovered the effects ofAXR1 andROP2 during trichome development, and revealed a pathway ofROP2 ‐mediated regulation of plant cell morphogenesis in Arabidopsis. -
null (Ed.)Glycosyltransferase OGT catalyzes the conjugation of O-linked β-D-N-acetylglucosamine (O-GlcNAc) to Ser and Thr residues of the cellular proteins and regulates many key processes in the cell. Here, we report the identification of OGT as a ubiquitination target of HECT-type E3 ubiquitin (UB) ligase E6AP, whose overexpression in HEK293 cells would induce the degradation of OGT. We also found that the expression of E6AP in HeLa cells with the endogenous expression of the E6 protein of the human papillomavirus (HPV) would accelerate OGT degradation by the proteasome and suppress O-GlcNAc modification of OGT substrates in the cell. Overall, our study establishes a new mechanism of OGT regulation by the ubiquitin–proteasome system (UPS) that mediates the crosstalk between protein ubiquitination and O-GlcNAcylation pathways underlying diverse cellular processes.more » « less
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