Poster: Proteomics

Abs # 969: Identification of DNA Replication Proteins Associated with the Chloroplast Nucleoid

Presenter:	Lassen, Matthew G., mattnerika@yahoo.com
Authors	Lassen, Matthew G. (A)   Nielsen, Brent L. (A)
Affiliations:	(A): Brigham Young University

During the early stages of plant development, chloroplasts maintain an extremely high copy number of up to 10,000-12,000 genome copies per cell. High levels of ctDNA replication are observed with proteins that co-purify with the chloroplast nucleoid (ct-nucleoid). The size, number, and structure of these nucleoids appear to change depending on the stage of chloroplast development, and therefore may play a role in regulating ctDNA replication and copy number. To date only four proteins associated with ct-nucleoids have been identified and characterized, all of which appear to have regulatory functions in transcription and/or replication. We reasoned that additional proteins involved in ctDNA replication may associate with the ct-nucleoid. The goal of this project is to identify nucleoid-associated proteins by mass spectrometry. To identify these replication proteins, isolated ct-nucleoid proteins from young soybean or Arabidopsis thaliana plants were separated on a SDS-polyacrylamide gel. MALDI mass spectrometry will be used to obtain a peptide profile unique for each protein analyzed, which can then be matched to the predicted protein profile of the soybean or Arabidopsis sequence. Identified proteins that show homology to replication proteins from other organisms will be chosen for gene expression analysis in various tissues during different stages of plant development. This study may provide important information in the elucidation of the unique chloroplast replication process. This work is supported in part by USDA/NRICGP.