Frequent DNA Transfer Among Mitochondrial, Plastid and Nuclear Genomes of Rice During Evolution

Abstract

Mitochondria and plastids are semiautonomous organelles that contain their own DNA. During evolution, it is thought that most of the genes of ancestral mitochondria and plastids, which appear to have originated from endosymbionts such as a proteobacterium and a cyanobacterium, respectively, have been transferred to the nuclear genome (as reviewed by Timmis et al. 2004). In addition to the transfer of functional genes from mitochondria and plastids to the nucleus, non-functional organelle-derived DNA segments are also found in the nuclear genome. Although most of the genes that function in mitochondria and plastids in higher plants have been transferred to the nuclear genome, the mitochondrial genome still contains 50–60 genes (Sugiyama et al. 2005) and the plastid genome still contains 100–150 genes (Sugiura and Takeda 2000).