Evolutionary history of the calvin cycle genes
Schnarrenberger, C.1 and Martin, W.2
1Freie Universität Berlin, Institute for Plant Physiology and Microbiology,
Königin-Luise-Str. 12-16a, D-14195 Berlin
2Institut für Genetik, Universität Braunschweig, Spielmannstr. 7,
D-38023 Braunschweig, Germany
In higher plants the Calvin cycle is encoded by 12 genes, all of them (with the exeption of Rubisco LS) being encoded by nuclear genes. The genes of the Calvin cycle are usually considered to have originated through an endosymbiontic event with a cyanobacterial progenitor organism, precedants of todays chloroplasts. Testing this hypothesis by gene tree analysis, we succeeded in cloning the remainder 4 enzyme genes (TPI, RPI, RuPE and transketolase), thus completing sequencing of all Calvin cycle enzymes from one plant (spinach). The following conclusions were to be drawn: (i) All genes of Calvin cycle originated from eubacteria. (ii) A large gene cluster present in alpha-proteobacteria is totally resolved in Synechocystis and higher plants. (iii) The gene duplications leading to chloroplast and cytosolic isoenzymes in plants occurred either in bacterial (GAPDH), early eukaryote (aldolase) or early plant evolution (3PGK, TPI and FBPase). (iv) In two cases (TPI and FBPase), the closest sequence homology of Calvin cycle genes was encountered with alpha-proteobacterial sequences, implying a gene transfer from bacteria to plants through an endosymbiosis along mitochondrial evolution. (v) From the original genes introduced from cyanobacteria to chloroplasts (and today present in the nucleus), only a some persisted in todays plants, others were substituted by nuclear genes encoding cytosolic enzymes. (vi) The presence of plastid and cytosolic aldolases of class I type in higher plants and of class II type in Cyanophora paradoxa (with no sequence homology whatsoever) indicates that such isoenzymes could have evolved twice independently in evolution. The results suggest that the physiological entity of the Calvin cycle in higher plants relies on genes with a very different phylogenetic history.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Monday, April 6 |
08:30 am |