Heterogeneity in endogenous amino acid pools of Chlamydomonas reinhardtii and C. eugametos

Levels of endogenous amino acid pools were measured for two species of the unicellular green alga Chlamydomonas. In C. reinhardtii, opposite mating types, designated + and −, of strain 137c were examined. The soluble pool of glutamic acid was most abundant in strain 137c−. In strain 137c+ similar levels of this amino acid were present, and high levels of cystine were observed. A soluble pool for the amino acid methionine was not detected in either strain. In opposite mating types of C. eugametos (strain Nos. 9 and 10), a soluble pool of alanine was most abundant, whereas neither cystine nor methionine were detected. When C. reinhardtii strain 137c+ was grown in the dark, cystine was not detectable, and proline markedly increased. Similarly, growth of strain 137c+ on nitrogen-deficient medium supplemented with a limited amount of arginine as a nitrogen source resulted in an apparent disappearance of pools of cystine. No apparent difference in the growth patterns of strains 137c+ and 137c− was observed. Tetrad analysis indicates that the high cystine content found in strain 137c+ is neither a characteristic of mating type nor under control of a single Mendelian gene. Key words: Chlamydomonas reinhardtii, Chlamydomonas eugametos, amino acid pool, cystine.