Effect of light on ribonucleic Acid metabolism in greening maize leaves

The effect of illumination on the incorporation of labeled precursors into RNA of dark-grown maize (Zea mays) leaves was studied using either (32)P-phosphate or double labeling with (14)C- and (3)H-uridine. In the dark, label was preferentially incorporated into etioplast ribosomal RNAs. Incorporation into this fraction and into lower molecular weight fractions was strongly and preferentially stimulated by light during the first 2 hours of illumination. The effect persisted after illumination was terminated. The possibility that light-induced alterations in plastid ribosomal RNA metabolism may not be required for chlorophyll accumulation in maize is discussed.Sucrose density gradient analyses of ribosomes and of extracted RNA did not reveal light-induced incorporation of label into messenger-like RNA associated with polyribosomes during brief illumination. However, newly produced RNA which seems to be neither ribosomal RNA nor transfer RNA is detectable after illumination for 2.5 hours or longer.