Ubiquitin-mediated proteolysis plays a
key role in the control of many different
cell functions, such as cell-cycle
progression, endocytosis, protein sorting,
regulation of transcription factors and
receptor desensitization [1]. Target
proteins are first modified through the
concerted actions of E1, E2 and
E3 enzymes and the polyubiquitylated
proteins are then degraded by
26S proteasomes. Compared with
S. cerevisiae, C. elegans and
Drosophila, Arabidopsis contains an
over-representation of genes encoding
ubiquitin conjugases and ubiquitin
protein ligases [2], suggesting the
importance of regulated proteolysis
in plant developmental processes.
Plant responses to endogenous signals
and environmental cues are mediated by
several hormones which are implicated in
almost every aspect of plant growth,
from seed germination to flowering.
Ubiquitin-mediated proteolysis has been
shown to regulate different steps of plant
hormone signal transduction. Here, we
focus on recent advances on the role of
proteasome-mediated degradation in
hormone signaling.