Abscisic acid‐induced cytoplasmic translocation of constitutive photomorphogenic 1 enhances reactive oxygen species 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 reactive oxygen species (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 ABAmediated inhibition of seed germination. These findings enhance the role of COP1 in the ABA signal transduction pathway.

Rice protein phosphatase 1 regulatory subunits OsINH2 and OsINH3 participate actively in growth and adaptive responses under abscisic acid

“…Recently Chen et al (2022) reported that ABA induces ROS which represses seed germination and induces osmotic stress. Thus, we observed ROS accumulation in all genotypes under normal conditions and ABA.…”

“…Recently, Chen et al (2022) have reported that ROS generation by ABA causes inhibition of seed germination, which recommended that mutation in OsINH2 and OsINH3 may inhibit seed germination through ROS, thus we investigated ROS accumulation. ROS is a secondary messenger which mediates different responses in the cell being disrupted by various stressors.…”

COP1‐ERF1‐SCE1 regulatory module fine‐tunes stress response under light‐dark cycle in Arabidopsis

“…Recently, many studies also showed that COP1 participated in stress responses through its translocation ability. ABA treatment induced the cytoplasmic translocation of COP1 and enhanced reactive oxygen species accumulation during seed germination (Chen et al, 2022). However, under prolonged treatment in seedlings, ABA-induced the nuclear translocation of COP1 and promoted salt stress tolerance by destabilising golden2-like1 protein to supress chloroplast development (Lee et al, 2021).…”

Integration of ABA, GA, and light signaling in seed germination through the regulation of ABI5

“…ABA induces nuclear accumulation of COP1 in the dark, thus activating COP1-mediated ABD1 degradation and ABI5 protein accumulation ( Peng et al, 2022 ). In contrast, COP1 negatively regulates ABA-mediated seed germination inhibition, as the cop1 mutant shows hypersensitivity to ABA under both light and dark conditions ( Chen et al, 2022 ; Peng et al, 2022 ). Under light conditions, ABA promotes COP1 enrichment in the cytoplasm, leading to the accumulation of HY5 and ABI5 proteins in the nucleus and increased ROS levels in seeds ( Chen et al, 2022 ).…”

“…In contrast, COP1 negatively regulates ABA-mediated seed germination inhibition, as the cop1 mutant shows hypersensitivity to ABA under both light and dark conditions ( Chen et al, 2022 ; Peng et al, 2022 ). Under light conditions, ABA promotes COP1 enrichment in the cytoplasm, leading to the accumulation of HY5 and ABI5 proteins in the nucleus and increased ROS levels in seeds ( Chen et al, 2022 ). But how COP1 regulates ABI5 during seed germination under dark is still unclear.…”