In Arabidopsis and many other plant species, anthocyanin pigments accumulate only after light exposure and not in darkness. Excess light of very high fluence rates leads to a further, very strong increase in anthocyanin levels. How excess light is sensed is not well understood. Here, we show that mutations in the key repressor of light signaling, the COP1/SPA complex, cause a strong hyperaccumulation of anthocyanins not only under normal light but also under excess, high light conditions. Hence, normal light signaling via COP1/SPA is required to prevent hyperaccumulation of anthocyanins under these high light conditions. However, since cop1 and spa mutants show a similar high-light responsiveness of anthocyanin accumulation as the wild type it remains to be resolved whether COP1/SPA is directly involved in the high-light response itself.
Keywords: COP1, constitutive photomorphogenic 1; COP1/SPA; CRY1, cryptochrome 1; HY5, elongated hypocotyl 5; PAP, production of anthocyanin pigment; SPA, supressor of phytochrome A-105; anthocyanin; high light; light; photomorphogenesis; signaling; stress.