TRMS: An Integrative Study of Plant Mitochondrial Biology

PI: Sally Mackenzie (University of Nebraska) CoPIs: Alan Christensen (University of Nebraska), Tom Elthon (University of Nebraska), Dong Wang (University of Nebraska) Collaborator: Andrew Benson (University of Nebraska)

Plant mitochondrial genomes have undergone a number of changes in their structure and maintenance properties that distinguish them from their mammalian counterparts. Most plant genomes characterized to date are a complex collection of linear and circular interconverting molecules that display evidence of recombination, foreign DNA integration and changes in relative copy number. These genomic activities are controlled by nuclear genes that can be manipulated in their expression to cause mitochondrial genome instability. Using this approach in tomato, tobacco, millet, sorghum, soybean and Arabidopsis allows for cross-species comparison of mitochondrial genome disruption. This project exploits this system to identify cellular and developmental pathways that are directly influenced by mitochondrial genome status, conserved across plant species, and evidenced by changes in plant phenotypes. The central hypothesis of the project states that mitochondrial status in plants is integrated into discrete pathways for plastid development, pollen development, cell cycle control and particular plant stress responses. The project provides unique entry to these pathway integration points by combining Arabidopsis mutant analysis and cross-species comparisons with mitochondrial and gene expression analysis. While it has long been known that plant mitochondria play distinct roles in metabolism, growth and development, direct mitochondrial manipulations prior to this study were largely restricted to inhibitor studies with limited opportunity for extrapolation to whole plant phenotype.

Broader impacts of the study.

Plant mitochondrial genome rearrangement can lead to altered plant phenotypes of agricultural importance. For example, these studies have already produced evidence of cytoplasmic male sterility, a trait useful in hybrid seed production and transgene containment, and of enhanced crop thermotolerance. Both valuable traits are difficult to attain using conventional crop breeding approaches. With regard to training opportunities, the Center for Plant Science Innovation (PSI) at University of Nebraska sponsors an undergraduate summer internship program that integrates to the proposed project; through this program, four minority students have already been recruited into graduate programs in the past two years. The PSI also directs the Nebraska Molecular Plant Breeding Graduate Program; this project sponsors at least two plant breeding students on the proposed project. Currently, the US faces a critical shortage of plant breeders with cross-cutting expertise in field management of transgenic crops, DNA marker-based selection, statistics, and comparative genomics. This project provides fertile ground for such training, in cooperation with plant breeders on campus and in industry.

Project data will be accessible via http://psiweb.unl.edu/mackenzie/ and gene expression data released to ArrayExpress (http://www.ebi.ac.uk/microarray-as/ae/).