The Nielsen Laboratory

We have two major research projects: 1. plant organelle DNA maintenance; 2. gene expression and proteomics analysis in halophytes.

Mitochondria are the powerhouses of eukaryotic cells and produce ATP for cellular processes. Chloroplasts are the site of photosynthesis. Both of these organelles contain DNA (mtDNA and ctDNA) that encodes only a few essential genes, while most proteins for mitochondrial and chloroplast function are encoded in the nucleus and must be imported into the organelles. We are interested in the mechanisms by which organelle DNA is replicated and maintained.

Our laboratory has been working for many years to study plant genes encoding mtDNA and ctDNA replication and recombination proteins and to determine their role in the maintenance of the organelle genomes during plant development.  We are analyzing T-DNA insertion mutants


for each of these genes to determine the effect of disruption of
expression of each on plant development. Our findings indicate that the two dual-targeted DNA polymerases have different but partially overlapping functions in mitochondria and chloroplasts. In addition, there is growing evidence that both mitochondrial and chloroplast genomes in plants replicate by a recombination-dependent mechanism.

Halophytes are plants that grow optimally in salty soils and have potential for development as agricultural crops. However, little is known about the mechanisms and proteins expressed in these plants that allow them to be salt tolerant. We have completed the de novo transcriptome analysis for one halophyte, Suaeda fruticosa, and have identified genes that show differential expression at optimal salt conditions. We are now using MudPIT mass spectrometry to identify proteins expressed in plants grown under different salt conditions. This work will lead to a better understanding of how different plant species have developed the ability to grow at high salt levels. Some of these plants may be useful as crops for farmers in the U.S. and in developing countries that have high salinity soils.