Title: Effects of puromycin aminonucleoside on growth and chloroplast development of Euglena gracilis
Abstract: Dark-adapted or light-grown cells of Euglena gracilis show a marked inhibition in growth rate when grown in the light in the presence of the aminonucleoside of puromycin (AN) at concentrations of 50 μg/ml or more. Inhibition of cell division is not immediate, but occurs after several cell doublings. Chlorophyll accumulation in dark-adapted cells placed in the light under growing or non-growing conditions is not markedly affected by AN at doses sufficient to strongly inhibit growth rate (100 μg/ml). Electron micrographs of cells treated at this level indicate that normal chloroplast structures are formed. Abnormal chloroplast structures were seen only in cells treated with 500 μg/ml AN, a dose level at which normal chlorophyll/cell amounts accumulate. Several hypotheses are presented to explain the relative insensitivity of the chloroplast or proplastid to AN in the intact Euglena cell.