Poster: Organelle Biogenesis

Abs # 1129: An Arabidopsis dynamin-like protein, ADL2Ap, controls not only peroxisomal but also mitochondrial divisions

Presenter:	Mano, Shoji , mano@nibb.ac.jp
Authors	Mano, Shoji  (A) (B)  Nakamori, Chihiro  (A)   Kondo, Maki  (A)   Nishimura, Mikio  (A) (B)
Affiliations:	(A): Dept. Cell Biol, Natl. Inst. Basic Biol. (B): Dept. Mol. Biomechanics, Graduate Univ. Advanced Studies

Peroxisomes are single membrane-bound organelles that are found ubiquitously in eukaryotic cells and have a variety of functions, such as fatty acid b-oxidation, photorespiration and the scavenging hydrogen peroxide. Experiments with transgenic Arabidopsis in which peroxisomes are labeled with green fluorescent protein have revealed that peroxisomes undergo dramatic changes in size, shape, number and position within the cell. Although peroxisomes are thought to proliferate by the division of pre-existing peroxisomes, the components for peroxisomal division have not been completely characterized.

To better understand the division process of peroxisomes, we screened a number of Arabidopsis mutants with aberrant peroxisome morphology (apm mutants). In one of these mutants, apm1, the peroxisomes are long and reduced in number, apparently as a result of inhibition of division. We show that this morphology is due to a mutation in a single gene, APM1, and that the gene product, Apm1p is a member of the dynamin-like protein family and have been annotated as ADL2Ap (Arabidopsis dynamin-like protein 2a). Mutations in Apm1p/ADL2Ap also caused aberrant morphology of mitochondria, double membrane organelles. This results show that the same dynamin molecule controls peroxisomal and mitochondria divisions in higher plants. We also report that fatty acid b-oxidation and photorespiration, which are cooperative functions of peroxisomes and mitochondria in higher plants, are markedly repressed in apm1, and that aberrant peroxisomes are more abundant in root cells, whereas aberrant mitochondria are more abundant in leaf cells, which indicates that the divisions of these organelles are organ-dependently regulated.