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. 2022 Feb 28;34(6):2286–2308. doi: 10.1093/plcell/koac073

Figure 9.

Figure 9

A working model depicting the role of COP1 in mediating ABA signaling during Arabidopsis seedling growth in darkness. During Arabidopsis seedling growth in darkness, COP1 promotes ABI5 stability by targeting ABD1 for 26S proteasome pathway-mediated degradation. In addition, COP1 also promotes the stability of PIF proteins in the dark. As PIFs and ABI5 itself can activate ABI5 transcription by directly binding to the G-box motifs in the ABI5 promoter (Xu et al., 2014; Qi et al., 2020), COP1 also mediates ABA-induced ABI5 transcription in the dark. Thus, COP1 mediates ABA-induced ABI5 accumulation through transcriptional and post-translational regulatory mechanisms, thereby playing a positive role in mediating ABA signaling during Arabidopsis seedling growth in darkness. ABA signaling induces the nuclear accumulation of COP1 in darkness, thus enhancing its activity in propagating the ABA signal.