Emeritus Professor
Division of Biological Sciences
Cell & Molecular Biology, Genetics & Plant Breeding, Genomics & Proteomics,
Research
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.