A rapidly light-induced chloroplast protein with a high turnover coded for by pea nuclear DNA.

Among the translation products obtained in vitro with mRNAs isolated from etiolated grown pea, or after different times of illumination following the etiolation, a 24000-Mr protein has been observed in the very early phase of greening; its occurrence culminates at 2-4 h after the start of illumination. From these data it is concluded that the corresponding mRNA appears in and disappears from the poly(A)-containing RNA population within hours. The protein product has been characterized as the precursor for a 17000-Mr chloroplast protein; by means of post-translational transport in vitro, the processed product becomes bound to chloroplast membranes. A product of the same size can also be labeled in vivo with a maximum of incorporation of label at 6-8 h after illumination. This product decays with a half-life of about 5 h. These findings imply a regulatory function of the 17000-Mr protein during the process of greening, possibly by synchronization of nuclear and chloroplast genomes. Other possibilities are considered.