Functional divergence of the repressors of photomorphogenesis SPA2 and SPA3 during Arabidopsis seedling deetiolation.

SPA2’s N-terminal kinase domain drives light-grown instability and stronger repression than SPA3, linking phytochrome A binding to selective SPA2 degradation in Arabidopsis seedlings.

• Why it matters: COP1/SPA controls photomorphogenesis, but how SPA2 versus SPA3 achieve distinct light responses is unclear, limiting understanding of how seedlings switch programs when light appears.
• What they did: Using domain-swap transgenic Arabidopsis seedlings, the study tested how SPA2 and SPA3 domain composition affects protein stability and repression, including binding of phytochrome A and activity of coiled-coiled and WD-repeat regions.
• The result: SPA2 instability correlates with phytochrome A binding and promotes CUL4DET1/COP1-dependent degradation of SPA2 but not SPA3, while SPA2’s coiled-coiled/WD-repeat domains repress photomorphogenesis more strongly, enabling light-triggered reduction of COP1/SPA activity.

AI summary of the abstract · may contain errors · not medical advice · read the paper.