Abstract
Arabidopsis AtbZIP10 is a bZIP transcription factor which participates in various cellular environmental responses as programmed cell death, disease resistance and osmoregulation. Our preliminary experiment supposed that Arabidopsis group-C bZIP transcription factors (bZIP-C: AtbZIP9,10,25,63) is very unstable in plant cells. Here we tried to figure out the mechanism of selective degradation of AtbZIP10 via ubiquitination by focusing on 26S proteasome-mediated degradation. Time-dependent degradation of AtbZIP10-GFP transiently expressed in Arabidopsis mesophyll protoplasts was inhibited by 26S proteasome inhibitor, MG-132. Deletion analysis of AtbZIP10-GFP demonstrated that this degradation can be inhibited by lacking domain II, which is highly conserved among bZIP-C. Since domain II contains some highly conserved lysine residues, known as ubiquitination target, bZIP-C including AtbZIP10 would be regulated by selective degradation via ubiquitination. Since now ubiquitination of AtbZIP10 has been confirmed by in vitro ubiquitination assay, we'll present this result, too.
