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PMID:19234086

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Citation

Lee, HK, Cho, SK, Son, O, Xu, Z, Hwang, I and Kim, WT (2009) Drought stress-induced Rma1H1, a RING membrane-anchor E3 ubiquitin ligase homolog, regulates aquaporin levels via ubiquitination in transgenic Arabidopsis plants. Plant Cell 21:622-41

Abstract

Ubiquitination is involved in a variety of biological processes, but the exact role of ubiquitination in abiotic responses is not clearly understood in higher plants. Here, we investigated Rma1H1, a hot pepper (Capsicum annuum) homolog of a human RING membrane-anchor 1 E3 ubiquitin (Ub) ligase. Bacterially expressed Rma1H1 displayed E3 Ub ligase activity in vitro. Rma1H1 was rapidly induced by various abiotic stresses, including dehydration, and its overexpression in transgenic Arabidopsis thaliana plants conferred strongly enhanced tolerance to drought stress. Colocalization experiments with marker proteins revealed that Rma1H1 resides in the endoplasmic reticulum (ER) membrane. Overexpression of Rma1H1 in Arabidopsis inhibited trafficking of an aquaporin isoform PIP2;1 from the ER to the plasma membrane and reduced PIP2;1 levels in protoplasts and transgenic plants. This Rma1H1-induced reduction of PIP2;1 was inhibited by MG132, an inhibitor of the 26S proteasome. Furthermore, Rma1H1 interacted with PIP2;1 in vitro and ubiquitinated it in vivo. Similar to Rma1H1, Rma1, an Arabidopsis homolog of Rma1H1, localized to the ER, and its overexpression reduced the PIP2;1 protein level and inhibited trafficking of PIP2;1 from the ER to the plasma membrane in protoplasts. In addition, reduced expression of Rma homologs resulted in the increased level of PIP2;1 in protoplasts. We propose that Rma1H1 and Rma1 play a critical role in the downregulation of plasma membrane aquaporin levels by inhibiting aquaporin trafficking to the plasma membrane and subsequent proteasomal degradation as a response to dehydration in transgenic Arabidopsis plants.

Links

PubMed PMC2660634 Online version:10.1105/tpc.108.061994

Keywords

Amino Acid Sequence; Aquaporins/metabolism; Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins/metabolism; Capsicum/genetics; Cell Membrane/metabolism; Droughts; Endoplasmic Reticulum/metabolism; Green Fluorescent Proteins/analysis; Intracellular Membranes/metabolism; Molecular Sequence Data; Plant Proteins/chemistry; Plant Proteins/genetics; Plant Proteins/physiology; Plants, Genetically Modified/metabolism; Proteasome Endopeptidase Complex/metabolism; Protein Transport/physiology; Recombinant Fusion Proteins/analysis; Sequence Alignment; Stress, Physiological; Ubiquitin-Protein Ligases/chemistry; Ubiquitin-Protein Ligases/genetics; Ubiquitin-Protein Ligases/physiology; Ubiquitination

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:RMA1

located_in

GO:0005783: endoplasmic reticulum

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

ARATH:RMA1

acts_upstream_of_or_within

GO:0032527: protein exit from endoplasmic reticulum

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:PIP21

enables

GO:0031625: ubiquitin protein ligase binding

ECO:0000353: physical interaction evidence used in manual assertion

UniProtKB:Q6R567

F

Seeded From UniProt

complete

CAPAN:RMA1

enables

GO:0005515: protein binding

ECO:0000353: physical interaction evidence used in manual assertion

UniProtKB:P43286

F

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0016567: protein ubiquitination

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0006970: response to osmotic stress

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0009723: response to ethylene

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0009611: response to wounding

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0009414: response to water deprivation

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0009409: response to cold

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

CAPAN:RMA1

located_in

GO:0005789: endoplasmic reticulum membrane

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

CAPAN:RMA1

enables

GO:0004842: ubiquitin-protein transferase activity

ECO:0000315: mutant phenotype evidence used in manual assertion

F

Seeded From UniProt

complete

CAPAN:RMA1

involved_in

GO:0043161: proteasome-mediated ubiquitin-dependent protein catabolic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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