Biogenesis of chloroplast membranes: XII. The influence of chloramphenicol on chlorophyll fluorescence yield and chlorophyll organisation in greening cells of a mutant of Chlamydomonas reinhardi y-1

Abstract

The initially high fluorescence yield of the dark-grown Chlamydomonas reinhardi y-1 cells decreases rapidly during the greening process. The decrease in fluorescence is markedly reduced if the greening is carried out in the presence of chloramphenicol (CAP). In the present work an attempt was made to find out whether the effect of CAP is due to an inhibition of electron transfer or formation of photosystem II quencher (Q), or to a change in the organisation of chlorophyll in the developing membranes. To this end the effect of DCMU and dithionite on the fluorescence yield and the absorption spectra of membranes from normal and CAP-treated cells were measured. The fluorescence of membranes formed in the fresence of CAP was enhanced by DCMU and dithionite even more than that of normal membranes suggesting that the effect is not due to a block in electron transfer or lack of Q. During greening the absorption spectrum is shifted from 672 nm to 680 nm due to accumulation of chlorophyll absorbing at 685 nm. This red shift is partially inhibited by CAP. Since a good correlation in time was found between the appearance of the red shift and the decrease in fluorescence it appears that CAP affects the organisation of chlorophyll in the membranes probably due to a block in the synthesis of chloroplast-made proteins.