Concluding remarks
Ubiquitin-mediated protein degradation
has recently emerged as a common
mechanism underlying plant hormone
signaling. This is perhaps not surprising
because at least in the case of auxin,
jasmonic acid and GA, accumulating
genetic and biochemical evidence suggests
that hormone signal transduction
pathways are negatively regulated
by repressors whose inactivation is
triggered by the cognate hormone.
One effective way to inactivate repressors
involves their ubiquitylation and
subsequent destruction via the
26S proteasomes (Fig. 2).