Chloroplast DNA is remarkably conservative in an evolutionary sense, with its genes governed by a slower "molecular clock" than are nuclear genes. This observation implies that the enzymes of chloroplast DNA replication and repair maintain a high level of fidelity in the maintenance of the chloroplast genome. Towards understanding the rules that govern this organelle genome, research projects in the Sears lab have investigated the controls of chloroplast DNA replication, the inheritance of chloroplasts, nuclear genes that affect the fidelity of chloroplast and mitochondrial DNA maintenance, and organelle mutation events, particularly replication slippage.

petri dishesTo study the mutation process, we have used the unicellular green alga Chlamydomonas reinhardtii because its small size allows billions of cells to be analyzed in a single experiment. In studying spontaneous mutations in the chloroplast DNA, we have observed a predominance of mutations resembling those that would be caused by oxidative damage. We hypothesize that under the high light growth conditions experienced by our Chlamydomonas cell lines, the chloroplast DNA repair systems may not have been able to handle all of the damage caused by the oxygen generated by the water-splitting activity of photosynthesis. We are currently testing the susceptibility of chloroplast DNA to photo-oxidative stress under various conditions, and we are seeking to determine if the high copy number of chloroplast DNA serves as a buffer to mutational damage.

An on-going collaboration with the laboratory of Christoph Benning has sought to understand the genetic basis and regulatory controls of lipid synthesis in microalgae. Chlamydomonas reinhardtii has been used as a model system because of the many genetic and molecular tools and strain resources that are available. Recent efforts have expanded to Nannochloropsis oceanica, which has promise as an alternative microalga for oil production.


In my terminal academic year prior to retirement, I am no longer responsible for ZOL/PBL 341 - Fundamental Genetics. My duties still include GEN 840 - Genetics Writing Skills, which is directed towards second and third year graduate students in the Genetics Program. I am the Director of an Exchange Program between MSU and the University of Duesseldorf, through which both undergraduate and graduate students are able to have extended stays at the sister university and undertake molecular biology research under the supervision of cooperating faculty.

The last decade has allowed me to enjoy the enthusiasm and excitement of a number of talented undergraduates who pursued research in my laboratory, including Ngoc Nguyen, Matt Enell, Ethan Dawson-Baglien, Allison Blaine and Ryan Mayle, Ashita Nagori, Kevin Raehtz, and Dan Readett. My last undergraduate researcher, Sarah Jaslow, finished her project in the summer of 2012, and is now pursuing a doctoral degree at Duke University.