The Molecular Evolution Research Of Gene EPSPS In Brassicaceae Plant

Different genes are used to the research of phylesis because of their different evolutionary rate. To date, two main genes that apply to the research of family and the classes above family are rbcL and 18S rDNA. Comparatively, the evolutionary rate of proteins coded by the nuclear genes is four or five times as fast as the rate of the two formers. The rate of Ndh F is fast and suit to the phylesis research in family. The evolutionary rate of ribosome DNA is more fast and only suit to the phylesis between genus and species. The EPSP synthase is a necessary enzyme of the shikimate pathway and it is very conservative. The amino acid sequences of EPSP synthase between high plants have very high identity, but the identity of transport peptide of EPSP is as low as 23% between plants. At present, nobody have reported the phylesis research through DNA sequence of EPSP. An oligo-nucleotide primer was designed according to a conservative fragment of this gene of plants in GENEBANK. Two 3'-end coding sequences of this gene (including complete sequences of exon 8,7,6,5,4 and partial sequences of exon 3 ), one, 1097bp, and the other 1109bp, were successfully isolated from brassicaeae napus and brassicaeae campestris. The DNA sequence analysis shows that the two fragments are more than 90% identical to Orychophragmus violaceus, Arabidopsis thaliana and Brassicaceae napus. The analysis of these two sequences and reported sequences (three families, 15 sequences in total) by NJ method and the simplestprinciple shows, the evolutionary trees established by these two methods are consistent and the sequences of the same family constitute one group. The sequences of thaliana and the sequences of Brassicaceae each makes up a sub-group in it. The sequences of violaceus distribute in Brassicaceae sub-group and this phenomena shows that the relationship is very near. The result accords to the classical analysis and the 3'-end coding sequence is a good model of molecular evolution and is suit to be used to establish the evolution relation map between family and genus in plants. The NJ map and simplest principle map based on 3'end coding sequences are identical to the two maps based on the complete coding sequences. This shows that 3' end coding sequences of EPSP can replace the complete coding sequences to analyze the molecular evolution. Analysis of the variation of bases of EPSPs of Brassicaceae, solanaceae and poaceae indicate that the evolutionary rates of EPSPs are different between Brassicaceae and solanaceae and the rate in solanaceae is higher than the rate in Brassicaceae according to the total substitution rate of bases.