Direct phosphorylation of HY5 by SPA kinases to regulate photomorphogenesis in Arabidopsis

What is it about?

ELONGATED HYPOCOTYL5 (HY5) is a key transcription factor which promotes photomorphogenesis by regulating downstream growth programs. Here we show that SPA1 can directly phosphorylate HY5 in vitro and in vivo. Unphosphorylated HY5 is a preferred substrate for degradation by COP1-SPA complex, binds strongly to the target promoters, and is a physiologically active form. Collectively, our study revealed that SPA1 acts both negatively and positively to fine-tune the stability and activity of HY5 to regulate photomorphogenesis.

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