| Several aspects of the isolation, structure, organization and evolution of genomes from non-green algae have been addressed in this dissertation. The chloroplast chromosomes (genomes) of two rhodophytes, Porphyra yezoensis and Griffithsia pacifica, encode several genes not found in higher plant chloroplasts, and show little resemblance in gene arrangement compared to angiosperm chloroplast genomes. Although the two red algae appear to have the same gene complement, their chloroplast genomes differ, to some extent, in structure and organization. The genomes are distinguished from each other by the presence of a ribosomal DNA encoding inverted repeat in Porphyra and a major inversion of approximately 40 kb. These differences are likely to be of phylogenetic utility in evolutionary studies of the red algae. Both red algae contain the phycobiliprotein, Rubisco small subunit and elongation factor tufA genes in their chloroplasts.;Comparative analysis of chloroplast chromosomes from two chromophytes, Olisthodiscus luteus and Ochromonas danica, shows little similarity in their overall gene organization, with one exception. Both algae contain several photosystem II protein genes (psbA, psbC, psbD) encoded on their inverted repeat structures.;It is argued that despite differences in details of chloroplast genome organization between rhodophytes, chromophytes and chlorophytes, their genomes are remarkably similar in an overall sense and most likely had a monophyletic origin.;The conchocelis of Porphyra yezoensis contains several plasmid-like DNAs. Two of these plasmids are linear molecules, with one of them bearing sequence homology to a section of the chloroplast genome. Possible origins and utility of these plasmids are discussed.;A method for the isolation of high molecular weight DNA from various red, brown and green macroalgae is presented. The method is rapid, economical and yields DNA of sufficient purity for cloning, restriction enzyme analysis and southern blotting. |
