INCORPORATION DE POLYRIBONUCLEOTIDES SYNTHETIQUES DANS DES CHLOROPLASTES ISOLES DE TRITICUM AESTIVUM CV. OPAL

Abstract

The incorporation of polyribonucleotides in isolated wheat chloroplasts is studied. Different radioactive synthetic polyribonucleotides are mixed with a chloroplastenriched fraction which has been isolated rapidly to preserve the chloroplasts as much as possible. After reaction, a band of class I chloroplasts is isolated by flotation in a discontinuous sucrose gradient. Polyribonucleotide incorporation is determined by counting TCA precipitable radioactive molecules. The extent of degradation of the incorporated polyribonucleotides is estimated by polyacrylamide gel electroploresis. The results show that class I wheat chloroplasts are permeable to synthetic polyribonucleotides of different molecular weights. Incorporated polyribonucleotides are partially degraded within the chloroplasts. Incorporation is stimulated in the presence of ATP and light but it is also detected at 5 C without these factors, suggesting a passive incorporation mechanism.