9408193 Floyd The green algae (known formally as the Chlorophyceae) are a diverse group of organisms, placed together by biologists because of the nature of their photosynthetic pigments and storage products. It has become clear that they include several ancient evolutionary lines. The particular algal species chosen for this study represent major groups within the green algae whose origins and affinities are questionable. The analysis emphasizes molecular characters as markers of evolution. The DNA sequences of genes which code for the nuclear small subunit ribosomal RNA will be determined. These genes are referred to as the 18S rRNA genes. Traditional approaches using morphological and microscopic (ultrastructural) characters which can help to understand the evolutionary pattern in these algae are either unavailable, uninformative, or conflicting. Several interrelated topics are to be investigated. These include: (1) the taxonomic relationships between members of the algal order Tetrasporales, especially whether forms with four flagella on their zoopores (called quadriflagellate) or two flagella (biflagellate) are closely related, and whether the species of the Tetrasporales are closely related to other algal groups; (2) the origin and affinities of two groups of filamentous algae, the Chaetophorales and the Oedogoniales, including if they have a common origin, or are derived from other types of algae; and, (3) the relationship between these filamentous algae and a selected set of algae that do not produce motile cells at any time in their life history, for which appropriate cell ultrastructure information is unavailable. The 18S rRNA genes of approximately 40 species will be studied by using the polymerase chain reaction (PCR) to amplify copies of the gene, then sequencing the DNA products. The results of the current project can be compared with sequences of the 18S rRNA genes of the other algae already studied and with published data on algal 18S rRNA gene sequences. The relationships identified from the molecular analysis will be compared with those based on traditional morphological characters, and on ultrastructural studies.
