ISSN:
1615-6102
Keywords:
Bleached status removal
;
Chloroplast
;
Euglena gracilis
;
Myomycin
;
Plastid ultrastructure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary In this study, we attempted to remove the mutagenic action induced inEuglena gracilis by myomycin (MM), a new bleaching antibiotic studied in our laboratory, which inhibits plastid protein synthesis by stably interacting with 70 S ribosomes of the organelle. Since the drug is stable only in a restricted interval of pH (5.0 to 6.5) and the internal pH ofEuglena can vary considerably in function of the culture pH, the MM-bleached cells were cultured in the light in a medium having a pH unsuitable to maintain the stability of the compound (pH 8.0). In this condition, the cells effectively regained their capacity to regreen, but with kinetics which strongly differed from that of dark-grown wild-typeEuglena cells exposed to light. The process developed in 25–30 days and included two phases; the first was characterized by rudimentary plastids and photoinduced carotenogenesis at the cytoplasmic and plastidial level, the second by a progressive structural and functional evolution of the plastidial structures into chloroplasts. Consequently, from colourless the cultures first became orange, then olive-green and finally deep-green. The phenomenon, however, was not at all synchronized within or among cells, so that plastids in various stages of differentiation could exist together with fully-formed organelles. The unusual regreening kinetics is attributed to a gradual removal of the MM-block on the plastidial 70 S ribosomes so that only certain biosynthetic events may normally be achieved, while others are still blocked or delayed. Only when the MM-block is completely removed is the typical co-regulation restored and the cells again acquire their normal characteristics. The removal possibility of the MM-bleaching effect may be a useful tool both for the appropriate interpretation of the bleaching phenomenon and for the study of chloroplast biogenesis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01276970
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