Abstract
Endoreduplication is one of the special cell cycle which is defined as successive chromosomal DNA replication without cell division and is correlated with cell size. To examin its, segregation distortion 3 (sd3) was isolated from RIKEN Ds insertional mutants collection. sd3 showed short hypocotyls and decreased polyploidy under the dark. Corresponding gene of SD3 encodes a protein with high similarity to yeast Translocase on the Inner Mitochondrial membrane 21 (TIM21), which is a component of the TIM23 complex. Indeed, SD3 protein fused to GFP was localized in mitochondria. SD3 over-expression plants (SD3-ox) showed increased polyploidy and hypocotyl size. Additionaly, expression levels of some subunits of the respiratory-chain complexes and ATP synthase were up-regulated in SD3-ox. Furthermore, SD3-ox showed high ATP levels whereas sd3 showed low ATP levels. Moreover, treatment of seedling with mitochondrial electron transport inhibitor antimycin A resulted in short hypocotyls, decrease in polyploidy levels and ATP levels. Here we speculate that mitochondrial protein regulates endocycle through cellular ATP levels in dark-grown seedlings.
