Molecular Markers And Phylogenetic Analysis Of Fatty Acid Synthesis Genes On Brassica

Brassica is the most important and one of the largest genera, consisting of more than 300 families, of Cruciferae plants. Many of them are vegetables, oil crops and feed crops commonly consumed and used in the world. Among these, heading and nonheading Chinese cabbages are especially cultivated in Chian and other Asian countries.Fatty acid biosynthesis is one of the primary metabolism pathways and therefore, very important in plant growth and development It is involved in many cellular processes, such as singnal transduction and resistance to biotic and abiotic stresses. Its products have been used in agriculture, chemical and food industry.This work stresses and tries to answer the question about the origin and phylogenetic relationship of Brassica six species based on the comparative analyses of important metabolic pathways at the gene and protein levels. Which complishment of the whole genome sequencing of Arabidopsis thalianan, which is very close to Brassica phylogenetically, many important genes have been characterized functionally. Most of these genes show high homology with those of Brassica speicies, and therefore paving the way for us to analyse their structural and functional relatioship among Brassica species.In this work, 9 pairs of PCR primers were designed and synthesized based on the conserved sequences of the genes in Arabidopsis, and used to amplify the genes for 9 different enzymes involved in faty acid biosynthesis from Brassica six species. After electrophoresis, distinct gene-specific band patterns were obtained. The data were then transformed into "0" and "1" matrix and the dendrogram was constructed using NTSYS software using neighbor-joining method. The gene fragments coding for fatty acid elongase (FAEI) and fatty acid desarurase (FAD2) were cloned into plasmids and sequenced.Based on our preliminary analysis of fatty acid biosynthetic pathway in Brassica, some conclusions have been reached:1, For the first time, the genes of fatty acid biosynthesis pathway were studied in Chinese cabbage.2, Every of the nine genes of fatty acid biosynthesis pathway has more than one copies and the copy number varies among different species and even some cultivars of the same speices.3, From the dendrogram, it could be seen mat, in species with the AA genome, heading Chinese cabbage and nonheading Chinese cabbage show higher similarity than any of them and turnip do. The species with the BB genome have relatively more distant relationship with other Brassica species. Among the three hybrid species, the AACC and BBCC genomes are the closest Genetically, the AABB genome has a longer distance from the BB genome man from the AA genome. Similarly, the BBCC genome is more distant from the BB genome than from the CC genome.4, All the gene sequences cloned in this work are highly conserved among Brassica six species, and these genes diflerenated before the speciation as shown in the phgylogenetic trees.5, Some genes, such as those coding for 3-oxoacyl-[acyl-carrier-protein] synthase and beta ketoacyl CoA synthase also show high similarity with FAE1, suggesting that these genes may have a common ancestor hi the evolution.