Exposure of dark grown resting EugIena to light induced the synthesis of chloroplast valyl-tRNA synthetase. Ethanol, a specific inhibitor of Euglena chloroplast development had little effect on chloroplast valyl-tRNA synthetase induction during the first 12h of light exposure. Ethanol, however, completely inhibited enzyme synthesis between 12-72h of Iight exposure. Malate, an alternative carbon source, had little effect on the photoinduction of valyl-tRNA synthetase. When dark grown resting cells were exposed to 2 h of light and returned to the dark, chloroplast valyl-tRNA synthetase continued to accumulate for 8-12h at a rate which was less than the rate in cells maintained continuously in the light. The mutant strain W3BUL lacks detectable chloroplast DNA and phototransformable protochlorophyllide, but retains a plastid remnant. Exposure of strain W3BUL to light induced the synthesis of chloroplast valyl-tRNA synthetase and enzyme induction was not inhibited by ethanol. After 72h of light exposure in the presence or absence of ethanol, enzyme levels in strain W3BUL were comparable to the levels found in the wildtype strain after 8-14h of light exposure. These results suggest that the nonchloroplast photoreceptor regulates the initial phase of enzyme synthesis. Mutant strain W10BSmL differs from strain W3BUL in that the plastid remnant if present, is greatly reduced. Chloroplast valyl-tRNA synthetase was undetectable in the strain WaoBSmL suggesting that the levels of active, cytoplasmically synthesized, chloroplast localized enzymes may be related to the developmental status of the chloroplast through the extent to which the enzyme precursor can be accumulated and or posttranslationally processed into an active enzyme within the chloroplast or chloroplast remnant.