Effect of Chloramphenicol on Amino Acid Incorporation by Chloroplasts and Comparison with the Effect of Chloramphenicol on Chloroplast Development in Vivo

Abstract

Amino acid incorporation into protein by chloroplasts and chloroplast ribosomes is more sensitive to inhibition by chloramphenicol than amino acid incorporation into protein by cytoplasmic ribosomes (3,4). Chloramphenicol also inhibits the formation of some chloroplast enzymes without affecting cell division in Euglena (11) or leaf development in bean (8,9). Chloramphenicol also selectively increases the proportion of 70 S ribosomes present as polysomes (6). Chloramphenicol is bound to chloroplast 70 S ribosomes but not to 80 S cytoplasm ribosomes of Euglena (1). These observations have led to the conclusion that chloramphenicol inhibits protein synthesis by chloroplasts, but not protein synthesis by the cytoplasm, as was suggested by Stutz and Noll (13 lated bean leaves (8). The inhibition by chloramphenicol of lightdependent development of photosynthetic activity varies in approximately the same way as the inhibition by chloramphenicol of amino acid incorporation into protein by chloroplasts (Fig. 1, upper). Likewise, inhibition by chloramphenicol of chlorophyll accumulation during illumination of etiolated leaves varies in the same way as inhibition by chloramphenicol of amino acid incorporation into protein by plastids (Fig. 1, lower). These correlations are meaningful only if the concentration of chloramphenicol in leaves during greening is approximately the same as the concentration of chloramphenicol applied to the leaves. Therefore, the absorption of chloramphenicol by leaves was measured. Leaves were treated with chloramphenicol solutions according to the procedure which was used previously to determine the effect of antibiotic on the formation of photosynthetic activity and chlorophyll (8). The chloramphenicol content of leaves was determined as follows. The leaves were picked, rinsed thoroughly, blotted dry, weighed, and stored frozen. The frozen leaves were ground with water in a Tenbroeck homogenizer. Insoluble material was removed by centrifugation and was washed once. Extract and washing were combined and heated 5 min at 100 C. Coagulated protein was removed by centrifugation and the supernatant liquids were stored frozen. Extracts were assayed for chloramphenicol by measuring inhibition of growth of Escherichia coli ATCC 10536 turbidimetrically (2,14).3 Extracts of leaves had no effect on the growth of E. coli unless the leaves had been treated with antibiotic. Heating standard solutions of chloramphenicol for 5 min at 100 C had no effect on the inhibition of growth of E. coli by chloramphenicol.Five hours after leaves were placed in 100 Ag/ml chloramphenicol, the concentration of antibiotic in the leaves was about 50 Ag/g fresh weight of leaves (Table I). This result shows that the concentration of chloramphenicol in leaves reaches half the concentration applied, early in the greening process. Thus, chlorophyll accumulation and formation of photosynthetic ac3The following modifications were made in the assay procedure.

Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

“…We found a decreased rate of the chlorophyll formation of the treated leaves and a decrease of the chlorophyll ajb ratio, similar to the results of Margulies and Brubaker (1970), Nikolaeva et al (1970) and Karimov et al (1974). The measured chlorophyll alb ratio of the treated leaves suggests a shifting of their pigment composition towards that of photosystem II.…”

Incorporation of 14C-Leucine into Apple Leaf Protein and Its Inhibition by Protein Synthesis Inhibitors during Growth and Senescence

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Cytokinin-induced changes of nitrogen remobilization and chloroplast ultrastructure in wheat (Triticum aestivum)

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