Evidence for a chimeric nature of nuclear genomes: eubacterial origin of eukaryotic glyceraldehyde-3-phosphate dehydrogenase genes.

Abstract

Plastids were once free-living prokaryotes and must have possessed all genes necessary for photoautotrophic growth at the time ofendosymbiosis. Yet higher plant chloroplast DNA encodes at least an order of magnitude fewer genes than the genomes of free-living prokaryotes. The majority of higher plant genes involved in photosynthesis, a metabolic pathway surely possessed by the endosymbiont, are currently located in the nucleus. Complete sequences for three plastid genomes have revealed that no known Calvin-cycle enzyme other than the large subunit of ribulose-bisphosphate carboxylase/ oxygenase is encoded by chloroplast DNA (for review see ref. 1). Under the gene-transfer corollary to the endosymbiotic theory, plant nuclear genes for those proteins essential to photoautotrophism in cyanobacteria (2) were ultimately de-rived from the endosymbiont's genome (3). They were transferred to the nucleus and their products were then reimported into the organelle of their origin with the help of a transit peptide (4, 5).In higher plants, glycolytic and Calvin-cycle pathways possess a number of enzymatic reactions in common which are catalyzed by distinct enzymes unique to each (6). In our previous studies of plant nuclear genes encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) enzymes of the Calvin cycle (GAPA and GAPB; EC 1.2

Exon shuffling and the origin of the mitochondrial targeting function in plant cytochrome c1 precursor.

“…If some GapC were to occur in the mitochondrion, the "presequence" in the donor gene would have served as an organelle targeter. However, the existence of GapC proteins in an organelle has not been reported to date although GapC genes are probably of mitochondrial origin (25,30), and the general belief is that all GapC is cytoplasmic. Thus we suggest that the donor shuffled sequence is important but not sufficient for organelle targeting activity.…”

Algal genomes reveal evolutionary mosaicism and the fate of nucleomorphs

“…Endosymbiotic gene transfer (EGT)-the movement of DNA from endosymbiont to host before, during and after the evolution of an organelle-has had a notable role in the evolution of algae and their nuclear genomes 28,29 . The genomes of eukaryotes that are known or proposed to have undergone secondary endosymbioses involving red or green algal endosymbionts are now regularly queried for the presence or absence of so-called 'red' genes or 'green' genes (for example, see refs 30, 31).…”

Horizontal gene transfer in evolution: facts and challenges

“…In addition, it has been shown that the acquisition of foreign genes from bacteria and other eukaryotes is also important in fungi (Richards et al 2006) and plant evolution (Martin et al 1993;Huang & Gogarten 2008), and has contributed to the evolution of bdelloid rotifers (Gladyshev et al 2008). On the other hand, horizontal gene transfer in eukaryotic evolution would be even more important if we consider animal and plant hybridization a massive horizontal gene transfer event, as well as the proposed role of hybridization in evolution (Seehausen 2004).…”