Circadian rhythm and phytochrome control of LHC-I gene transcription

A small amount of translatable mRNA for a nuclear-coded precursor apoprotein of the LHC-I (light-harvesting complex of photosystem I) with a molecular mass of 26 kDa is present in etiolated bean leaves. The expression of this protein is phytochrome-controlled and follows circadian oscillations, for the appearance of which a red-light pulse is sufficient. The rhythmical oscillations persist for many hours in the dark following the red-light pulse or in continuous white light. The similarity of this rhythm in the light-induced accumulation of LHC-I mRNA with that of LHC-II mRNA [(1989) Plant Physiol. 90, 665] suggests that the same oscillator may govern the expression of all chloroplast protein genes regulated by light.