Abstract
Endoreduplication is one of the special cell cycle which is defined as successive chromosomal DNA replication without cell division. In plants, endoreduplication is proposed to correlate with cell size. To reveal molecular mechanisms of endoreduplication, segregation distortion 3 (sd3) was isolated from Ds insertional mutants collection. sd3 showed short hypocotyl and decreased polyploidy under the dark. Corresponding gene of SD3 has high similarity to yeast Translocase on the Inner Mitochondrial membrane (TIM21), which is a component of the TIM23 complex. Consistent with this, localization of fusion protein SD3:GFP was observed in mitochondria. sd3 showed low ATP levels, suggesting that decrease in ATP levels was caused by declining in activity of mitochondria. Conversely, SD3 over-expression plants showed increased polyploidy and organ size. Interestingly, expression levels of some subunits of the respiratory-chain complexes III and IV were up-regulated in SD3 over-expression plants, suggesting also that endoreduplication was controlled by ATP levels. Here we speculate that mitochondrial protein regulates endocycle through cellular ATP levels.
