Alan C. Christensen
Alan Christensen
Professor

Ph.D. University of Washington, 1982
Contact Information
E205 Beadle Center
402.472.0681

Research Interests


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. Plant mitochondrial genomes only encode slightly more genes than animal mitochondria do (54 genes in Arabidopsis vs. 37 in humans). Most of the extra DNA is of unknown function. The genes of known function are among the slowest evolving (fewest mutations per generation) 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 recently proposed a model to explain the simultaneous findings of low mutation rates in genes and high rearrangement and mutation rates outside of genes.

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, and the American Society of Plant Biologists

University of Nebraska – Lincoln, College of Arts and Sciences Distinguished Teaching Award, 2008

Publications


  • 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., "Bacteriophage Lambda-based Expression Vectors", invited review, Molecular Biotechnology, 17: 219-224, 2001.
  • Christensen, A.C., "Cats as an aid to teaching genetics", Genetics, 155: 999-1004, 2000.
  • Barry, M. K., Triplett, A.A., and Christensen, A.C., "A Peritrophin-like protein expressed in the embryonic tracheae of Drosophila melanogaster", Insect Biochemistry and Molecular Biology, 29: 319-327, 1999.