Originally published as Genetics Published Articles Ahead of Print on July 18, 2006.

Genetics, Vol. 174, 707-718, October 2006, Copyright © 2006
doi:10.1534/genetics.106.060657

Arabidopsis SHORT INTEGUMENTS 2 Is a Mitochondrial DAR GTPase

Theresa A. Hill1, Jean Broadhvest2, Robert K. Kuzoff3 and Charles S. Gasser4

Section of Molecular and Cellular Biology, University of California, Davis, California 95616

4 Corresponding author: Section of Molecular and Cellular Biology, University of California, 1 Shields Ave., Davis, CA 95616.
E-mail: csgasser{at}ucdavis.edu

The Arabidopsis short integuments 2-1 (sin2-1) mutant produces ovules with short integuments due to early cessation of cell division in these structures. SIN2 was isolated and encodes a putative GTPase sharing features found in the novel DAR GTPase family. DAR proteins share a signature DAR motif and a unique arrangement of the four conserved GTPase G motifs. We found that DAR GTPases are present in all examined prokaryotes and eukaryotes and that they have diversified into four paralogous lineages in higher eukaryotes. Eukaryotic members of the SIN2 clade of DAR GTPases have been found to localize to mitochondria and are related to eubacterial proteins that facilitate essential steps in biogenesis of the large ribosomal subunit. We propose a similar role for SIN2 in mitochondria. A sin2 insertional allele has ovule effects similar to sin2-1, but more pronounced pleiotropic effects on vegetative and floral development. The diverse developmental effects of the mitochondrial SIN2 GTPase support a mitochondrial role in the regulation of multiple developmental pathways.