ABA-induced cytoplasmic translocation of COP1 enhances ROS accumulation
through the HY5-ABI5 pathway to modulate seed germination
Abstract
Seed germination is a physiological process regulated by multiple
factors. Abscisic acid (ABA) can inhibit seed germination to improve
seedling survival under conditions of abiotic stress, and this process
is often regulated by light signals. Constitutive Photomorphogenic 1
(COP1) is an upstream core repressor of light signals, and is involved
in several ABA responses. Here, we demonstrate that COP1 is a negative
regulator of the ABA-mediated inhibition of seed germination. Disruption
of COP1 enhanced Arabidopsis seed sensitivity to ABA and
increased ROS levels. In seeds, ABA induced the translocation of COP1 to
the cytoplasm, resulting in enhanced ABA-induced ROS levels. Genetic
evidence indicated that HY5 and ABI5 act downstream of COP1 in the
ABA-mediated inhibition of seed germination. ABA-induced COP1
cytoplasmic localization increased HY5 and ABI5 protein levels in the
nucleus, leading to increased expression of ABI5 target genes and ROS
levels in seeds. Together, our results reveal that ABA-induced
cytoplasmic translocation of COP1 activates the HY5-ABI5 pathway to
promote the expression of ABA-responsive genes and the accumulation of
ROS during ABA-mediated inhibition of seed germination. These findings
enhance the role of COP1 in the ABA signal transduction pathway.