Ph.D. University of Washington, 1982
B.S. University of Washington, 1976-77
(Biology & Chemistry)
E205 Beadle Center
Mitochondria are widely known as the “powerhouses” of the cell. They are the site of respiration and most of the energy generation in cells. What is less widely known is the other roles they play in the lives of organisms, including regulating reproductive strategies and controlling programmed cell death. Mitochondria have their own DNA and genetic system, although they rely on the nucleus for synthesis of many of their proteins.
Plant mitochondria are considerably more complex than animal mitochondria. Their genomes are much larger – some are more than one million base pairs in contrast to the sixteen thousand base pairs found in human mitochondria. Most of the extra DNA is of unknown function – there are very few extra known genes in plant mitochondria compared to other organisms. The genes of known function are among the slowest evolving known. At the same time, the genome rearranges readily and frequently and the noncoding parts of the genome are difficult or impossible to compare between species.
I am interested in the mechanisms of DNA replication, recombination and repair that maintain the mitochondrial genomes, as well as the mechanisms that allow them to expand and add so much noncoding DNA. I have proposed a model to explain the simultaneous findings of low mutation rates in genes and high rearrangement and mutation rates outside of genes. I also proposed that the non-coding DNA in plant mitochondria is functionless junk DNA.
My current work includes developing a method for transforming Arabidopsis mitochondria, as well as studying mechanisms of DNA repair in mitochondrial genomes.
Member of the Genetics Society of America, the American Association for the Advancement of Science, the American Society of Plant Biologists, and the Society for Molecular Biology and Evolution.
University of Nebraska – Lincoln, College of Arts and Sciences Distinguished Teaching Award, 2008
- Christensen, A.C., “Genes and Junk in Plant Mitochondria—Repair Mechanisms and Selection,” Genome Biology and Evolution, 6: 1448-1453, 2014.
- Christensen, A.C., “Plant mitochondrial genome evolution can be explained by DNA repair mechanisms,” Genome Biology and Evolution, 5: 1079-1086, 2013. This article was highlighted in Venton, D., “Highlight: The Mystery of Mitochondrial Genomes,” Genome Biology and Evolution, 5: 1115-1116, 2013.
- Shah, N., Dorer, D.R., Moriyama, E.N. and Christensen, A.C., “Evolution of a large, conserved and syntenic gene family in insects,” G3:Genes, Genomes, Genetics, 2: 313-319, 2012.
- Arrieta-Montiel, M., Shedge, V., Davila, J., Christensen, A.C. and Mackenzie, S.A., “Diversity of the Arabidopsis Mitochondrial Genome Occurs Via Nuclear-controlled Recombination Activity,” Genetics, 183: 1261-1268, 2009.
- Shedge, V., Arrieta-Montiel, M., Christensen, A.C. and Mackenzie, S.A., “Plant Mitochondrial Recombination Surveillance Requires Unusual RecA and MutS Homologs,” Plant Cell, 19: 1251-1264, 2007. This article was highlighted in Eckardt, N.A., “Mitochondrial Recombination Surveillance,” Plant Cell, 19: 1139, 2007.
- Abdelnoor, R.V., Christensen, A.C., Mohammed, S., Munoz-Castillo, B., Moriyama, H. and Mackenzie, S.A., “Mitochondrial genome dynamics in plants and animals: Convergent gene fusions of a MutS homolog,” J. Mol. Evol., 63: 165-173, 2006.
- Christensen, A.C., Lyznik, A., Mohamed, S., Elowsky, C.G., Elo, A., Yule, R. and Mackenzie, S.A., “Dual-domain, dual-targeting organellar protein presequences within higher plants can utilize non-AUG start codons,” Plant Cell, 17: 2805-2816, 2005.
- Dorer, D.R. Rudnick, J.A., Moriyama, E.N. and Christensen, A.C., "A Family of Genes Clustered at the Triplo-lethal locus of Drosophila melanogaster has an Unusual Evolutionary History and Significant Synteny with Anopheles gambiae", Genetics, 165:613-621,2003.
- Smoyer, L.K., Dorer, D.R., Nickerson, K.W. and Christensen, A.C., "Phenotype of the Triplo-lethal locus of Drosophila melanogaster and Its Suppression by Hyperoxia", Genetical Research, 82:163-170,2003.
- Abdelnoor, R.V., Yule, R., Elo, A., Christensen, A.C., Meyer-Gauen, G., and Mackenzie, S.A., "Substoichiometric shifting in the plant mitochondrial genome is influenced by a gene homologous to MutS", Proc. Nat. Acad. Sci., 100:5968-5973, 2003.
- Eissenberg, J.C., Ma, J., Gerber, M.A., Christensen, A.C., Kennison, J.A., and Shilatifard, A., "dELL is an essential RNA polymerase II elongation factor with a general role in development", Proc. Nat. Acad. Sci., 99: 9894-9899, 2002.
- Christensen, A.C., "Cats as an aid to teaching genetics", Genetics, 155: 999-1004, 2000.