Evolution of organelle genetic systems in green algae.

Our laboratory studies evolution in unicellular green algae using molecular biological and computational methods. Three specific areas of our current research are summarized below.

 

 Structural diversity in mitochondrial DNA conformation.

The ancestral mitochondrial genome of green algae appears to have been a circular unit-genome-size molecule as seen in most of the green algal lineages examined to date. However, the Reinhardtii clade (sensu Proschold et al. 2005) of the class Chlorophyceae appears to contain unit-genome-size linear and fragmented-linear forms. We are interested in the events which led to the linearization and fragmentation of the mitochondrial genome evident in the Reinhardtii clade.

Mitochondrial genome architecture and coding capacity.

A central question in molecular evolution is to identify the role of mutation rate and the power of random genetic drift in shaping mitochondrial genome architecture and coding capacity across lineages. Because the mitochondrial genome in different green algal lineages contains non-coding DNA (intergenic spacers and introns) that varies from less than 10% to more than 50% and a gene number that varies by a factor of five, they seem to represent an excellent group in which to investigate the evolutionary basis for this diversity.

 

Plastid functions in lineages which have lost the capacity for photosynthesis.

Chloroplasts perform many functions in addition to those involved in photosynthesis. Colorless, green algal lineages exist that have permanently lost the capacity for photosynthesis but still retain a plastid. We have been examining the nature of the functions occurring in these colorless plastids using EST sequences of nuclear genes that target their products to the mitochondria. We are examining relationships between the lifestyle of the lineage (e.g., free living or obligate parasitic) and the breadth functions performed in the plastid.