Abscisic Acid Increases Arabidopsis ABI5 Transcription Factor Levels by Promoting KEG E3 Ligase Self-Ubiquitination and Proteasomal Degradation

被引:243
作者
Liu, Hongxia [1 ]
Stone, Sophia L. [1 ]
机构
[1] Dalhousie Univ, Dept Biol, Halifax, NS B3H 4R2, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
SNRK2; PROTEIN-KINASES; PLANT DEVELOPMENT; SEED-GERMINATION; GROWTH; REGULATOR; DOMAIN; REPRESSORS; STRESS; FAMILY; MDM2;
D O I
10.1105/tpc.110.076075
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The Arabidopsis thaliana RING-type E3 ligase KEEP ON GOING (KEG) is a negative regulator of abscisic acid (ABA) signaling. Seedlings homozygous for T-DNA insertions in KEG accumulate high levels of the ABA-responsive transcription factor ABSCISIC ACID-INSENSITIVE5 (ABI5). Here, we demonstrate that KEG E3 ligase activity is required for the regulation of ABI5 abundance. KEG ubiquitinates ABI5 in vitro, and a functional KEG RING domain is required to restore the levels of ABI5 in keg-1 to that of the wild type. Overexpression of KEG leads to ABA insensitivity, which correlates with KEG protein levels. In the presence of ABA, ABI5 levels increase drastically via a decrease in ubiquitin-meditated proteasomal degradation. Our results indicate that ABA promotes ABI5 accumulation by inducing the ubiquitination and proteasomal degradation of KEG. A functional RING domain is required for the ABA-induced degradation of KEG, suggesting that the loss is due to self-ubiquitination. Mutations within KEG's kinase domain or treatments with kinase inhibitors prohibit the ABA-induced ubiquitination and degradation of KEG, indicating that phosphorylation, possibly self-phosphorylation, is involved in the ABA regulation of KEG protein levels. We discuss a model for how ABA may negatively regulate KEG protein abundance, leading to accumulation of ABI5 and ABA-dependent cellular responses.
引用
收藏
页码:2630 / 2641
页数:12
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