ABA and the ubiquitin E3 ligase KEEP ON GOING affect proteolysis of the Arabidopsis thaliana transcription factors ABF1 and ABF3. (19th July 2013)

• Record Type: Journal Article
• Authors: Chen, Yi‐Tze; Liu, Hongxia; Stone, Sophia; Callis, Judy
• Is Part Of: Plant journal. Volume 75:Number 6(2013:Sep.)
• Page Start: 965
• Page End: 976
• Publication Date: 2013-07-19
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12259
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12259-abs-0001"> <title>Summary</title> <p>The ABA Binding Factor/ABA‐Responsive Element Binding Proteins (ABF/AREB) subfamily of bZIP‐type transcription factors are positive effectors of ABA responses. Here, we examine the proteolytic regulation of two members: <italic>Arabidopsis thaliana </italic>ABF1 and ABF3. Both transcription factors are unstable in seedlings, and their degradation is sensitive to proteasome inhibition. ABA treatment of seedlings leads to their rapid accumulation, the result of slowed proteolysis. Deletion of the conserved C–terminal region required for 14–3–3 interaction destabilizes the proteins. The degradation of ABF1 and ABF3 are slower <italic>in vivo</italic> in seedlings lacking the ubiquitin E3 ligase KEEP ON GOING (KEG), and <italic>in vitro</italic> in extracts from <italic>keg</italic> seedlings, implicating KEG in their degradation. ABF1 and ABF3 are ubiquitylation substrates of KEG <italic>in vitro</italic>, and <italic>in vitro</italic> pull‐down assays document their direct interaction. In contrast to ABI5, another KEG substrate, the degradation of ABFs and proteolytic regulation of ABFs by ABA still occurs in <italic>keg</italic> seedlings, suggesting that additional E3s participate in ABF1 and ABF3 proteolysis. Loss of ABF1 or ABF3 in the <italic>keg</italic> background has a phenotypic effect similar to the loss of ABI5, and there is no additional rescue of the <italic>keg</italic> phenotype in <italic>abf1 abf3 abi5 keg</italic> seedlings. This result suggests that the abundance of other substrates is altered in <italic>keg</italic> seedlings, affecting growth. In conclusion, ABF1 and ABF3 abundance is affected by ABA and KEG, and the conserved C4 region serves as a stabilizing element.</p> </abstract>