Our research aims to clarify interactions among the plant cell's three genomes: nuclear, mitochondrial and chloroplast. Current projects include analyses of mitochondrial mutations and functional interactions between mitochondria and chloroplasts. We are also studying nuclear-mitochondrial interactions affecting mitochondrial gene expression and plant growth.

One of our long-term objectives is to understand the effects of individual mitochondrial genes on organelle biogenesis and overall cellular function in plants. By studying maternally inherited nonchromosomal stripe (NCS) mutations in maize, we have correlated specific mitochondrial DNA alterations with defective plant phenotypes. Each mutation is a deletion resulting from recombination between very small repeats within the mitochondrial genome. All the mutations cause cell death at some point during the plant life cycle. Thus, the mutations have been studied in heteroplasmic plants carrying normal mitochondria as well as defective organelles.

Sorting out during development leads to mutant sectors, which allows us to identify the phenotype associated with a specific mitochondrial lesion. Mutant kernels that normally abort can be rescued to generate homoplasmic callus cultures. These cultures do not regenerate plantlets. Tissue culture strains produced from deletion mutants are being used to develop mitochondrial transformation procedures for higher plants.

We expect that most of the components that regulate the expression of plant mitochondrial genes are coded for by the nucleus. To reveal some of the nuclear-mitochondrial interactions that must occur for normal plant growth, we are using a genetic approach that takes advantage of evolutionary divergence. Plants that have mitochondria from related wild species (teosintes) introduced into maize lines by standard genetic hybridizations can show altered mitochondrial properties, depending on which alleles of certain nuclear genes are present. Our laboratory is using this system to identify nuclear genes that affect mitochondrial gene expression.

Matera JT, Monroe J, Smelser W, Gabay-Laughnan S, and Newton KJ. Unique changes in mitochondrial genomes associated with reversions of S-type cytoplasmic male sterility in Maizemar . PLoS ONE 2011;6(8), art. no. e23405

Roark LM, Hui AY, Donnelly L, Birchler JA and Newton KJ. Recent and frequent insertions of chloroplast DNA into maize nuclear chromosomes. Cytogenetic and Genome Research 2010;129(1-3):17-23.

Gabay-Laughnan S, Kuzmin EV, Monroe J, Roark L and Newton KJ. Characterization of a novel thermosensitive restorer of fertility for cytoplasmic male sterility in maize. Genetics 2009;182(1):91-103.

Lough AN, Roark LM, Kato A, Ream TS, Lamb JC, Birchler JA and Newton KJ. Mitochondrial DNA transfer to the nucleus generates extensive insertion site variation in maize. Genetics 2008;178(1):47-55.

Kubo T and Newton KJ. Angiosperm mitochondrial genomes and mutations. Mitochondrion 2008;8(1):5-14.

Kuzmin EV, Duvick DN and Newton KJ. A mitochondrial mutator system in maize. Plant Physiology 2005;137(2):779-789.

Jiao S, Thornsberry JM, Elthon TE and Newton KJ. Biochemical and molecular characterization of photosystem I deficiency in the NCS6 mitochondrial mutant of maize. Plant Molecular Biology 2005;57(2):303-313.

Gabay-Laughnan S and Newton KJ. Mitochondrial mutations in maize. Maydica 2005;50(3-4):349-359.

Kuzmin EV, Karpova OV, Elthon TE and Newton KJ. Mitochondrial respiratory deficiencies signal up-regulation of genes for heat shock proteins. Journal of Biological Chemistry 2004;279(20):20672-20677.

Clifton SW, Minx P, Fauron CMR, Gibson M, Allen JO, Sun H, Thompson M, Barbazuk WB, Kanuganti S, Tayloe C, Meyer L, Wilson RK and Newton KJ. Sequence and comparative analysis of the maize NB mitochondrial genome. Plant Physiology 2004;136(3):3486-3503.

Birchler JA and Newton KJ. Discovering the seeds of diversity in plant genomes. Genome Biology 2004;5(5):

Karpova OV, Kuzmin EV, Elthon TE and Newton KJ. Differential expression of alternative oxidase genes in maize mitochondrial mutants. Plant Cell 2002;14(12):3271-3284.

Auger DL, Newton KJ and Birchler JA. Nuclear gene dosage effects upon the expression of maize mitochondrial genes. Genetics 2001;157(4):1711-1721.

• NSF boosts funding for plant genome research (Nov 2001)