Poster: Organelle biogenesis

Abs # 639: Developmental regulation of the bifunctional enzyme DCP68/SiR in Arabidopsis thaliana

Presenter:	Adamson, Steven W, steven.adamson@usm.edu
Authors	Adamson, Steven W (A)   Heinhorst, Sabine  (A)   Gordon, Cannon C (A)
Affiliations:	(A): University of Southern Mississippi

Plastids are a group of organelles whose function depends upon the cell type in which they reside. During plastid development, dynamic morphological changes in nucleoids have been observed, which are thought to arise from modifications in protein composition, protein/DNA interaction, and degree of compaction. An abundant member of plastid nucleoids is DCP68/SiR, a bifunctional DNA-binding protein that also participates in reductive sulfur assimilation. To explore whether developmental cues regulate the abundance of DCP68/SiR, transcript and protein levels were examined in young and mature leaf and root tissue and during culture of soybean SB-M cells. Differences in the transcript and protein abundance suggest that DCP68/SiR is regulated differently in root and leaf tissues. DCP68/SiR is a phosphoprotein, whose affinity for DNA is strongly enhanced upon in vitro dephosphorylation. Since posttranslational modification of nucleoid proteins may be a regulatory strategy used by the plant to modulate structure and function of plastid nucleoids, the isoelectric point of DCP68/SiR is being examined to assess potential changes in the phosphorylation state of DCP68/SiR during development.