Ribosome-Thylakoid Association in Peas

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Abstract
Isolated pea chloroplast thylakoids ordinarily have ribosomes attached which survive sequential washes. Extensive in vivo loss of these thylakoid-bound ribosomes occurred if the pea plants were placed in the dark without O2 for 2 or more hours. This loss was indicated from measurements of both the total thylakoid-bound RNA levels, and the capacity for amino acid incorporation into proteins on the addition of soluble enzymes for protein synthesis. Stroma ribosome profiles lost any indication of polysome structure due to the same anoxic treatment in vivo. The return of ribosomes to the thylakoids when plants were placed in the light in air occurred over 8 h. This return was prevented by lincomycin, spectinomycin and chloramphenicol, indicating a requirement for protein synthesis steps in the stroma at some point in the reassociation process.