Loss of ribosomes in Nicotiana glutinosa L. infected with lettuce necrotic yellows virus

Abstract

Changes that occur in the amounts of ribosomes and ribosomal RNA in leaves of Nicotiana glutinosa L. following systemic infection with lettuce necrotic yellows virus (LNYV) have been studied in relation to the development of infection and the onset of symptoms. In plants grown under continuous light, 70 S chloroplast ribosomes commenced to decline in concentration within 1 day of the appearance of symptoms, and were not detected 1–3 days later. Chloroplast ribosomal 16 S and 23 S RNA's were isolated in trace amounts only 1 day after symptoms appeared and incorporated negligible quantities of 32P; they then became undetectable. Growth of infected leaves almost completely ceased at this stage, virus content commenced to decline, and chloroplasts became smaller. Lower concentrations of cytoplasmic 80 S ribosomes were extracted from infected leaves after the 70 S ribosomes had declined, but this was not accompanied by a loss of cytoplasmic ribosomal 18 S and 25 S RNA or a failure to incorporate 32P. These changes were also observed in plants grown in the glasshouse and in plants infected with either a mild or a severe isolate of LNYV.