Effect of Chloramphenicol on Etiochloroplasts of Wild and Chlorophyll b-Less Barley Genotypes

Greening of etiolated seedlings of wild and Chl b-less barley(Hordeum vulgare L.) genotypes in the presence of D-threochloramphenicol(CAP) led to macrogranal arrangements accompanying the inhibitionof Chl synthesis and an enhancement of the total protein contentin differentiated etiochloroplasts. In treated mutant plastids,protein/Chl ratio reached up to 100. No light-dependent O₂ evolution was detected in CAP-treatedplastids which had deficiency in polypeptides belonging to thephotosystem II (PSII) centres. On the other hand, plastids displayeda high photosystem I (PSI) activity despite the absence of the92 kDa polypeptide linked to the PSI centre. The accumulationof polypeptides ranging from 16 to 20 kDa suggest that theycould originate from primary complexes consisting of few Chlmolecules, but they were sufficient to allow the activity ofthe reaction centres. No accumulation of the 25–27 kDapolypeptides linked to the PSII antenna was detected. The increase in the proportion of trans-₃hexadecenoic acid (16:1tr) in phosphatidylglycerol (PG) of etiochloroplasts from bothtypes after CAP treatment could indicate an alteration of theregulation process of 16:1 tr biosynthesis occurring in plastids.The formation of macrograna could optimize the energy transferin altered thylakoid membranes. The accumulation of PG-16:1tr molecules could be related to the formation of active primarycomplexes in thylakoid when Chl synthesis is altered. (Received March 30, 1988; Accepted June 1, 1988)