Genome Wide Distribution Of Differently Methylated Loci And Relationship With Important Agronomy Traits In Brassica Napus L.

As a conserved epigenetic mark, DNA methylation is involved in many important biological processes, including heterochromatin formation, defense against transposon proliferation, genomic imprinting, regulation of endogenous gene expression, and silencing of transgenes. Genomic DNA methylation has been researched broadly and deeply in A. thaliana, but rarely in main crops, especially in Brassica napus. We identified many differently cytosine methylated loci between two Brassica napus cultivars, Tapidor and Ningyou 7, on the genome wide with methylation sensitive AFLP (MS-AFLP) technique and analyzed the association between methylation loci and some key agronomy traits of oilseed rape.We used the 827 MS-AFLP markers gotten from our TN DH population to density the frame linkage map consisting 599 markers. One MS-AFLP marker represents a differently methylated locus in the genome DNA. The final map contains 507 methylation specific markers and 599 other kinds of markers. In order to analysis the distribution of methylation loci easily we constructed an epigenetic linkage map with the 507 methylation specific markers without changing their linkage distance.By assaying the distribution of detected methylation loci on each linkage group we found that both the number and the density are not identical in different linkage groups. The least and the most amount are 4 and 52 corresponding in C05 and A06 linkage group. The highest density is seven times of the lowest.We cut the genome into 10cM length intervals to analysis the distribution of methylation loci in detail. It uncovers that the methylation loci do not appear stochastically in a linkage group. The highest frequency is five times of the lowest one.Through comparing the average amount and the density of methylation loci between A genome and C genome, the average amount of A genome is more than C genome by 20%, but the densities are not significantly different. On the whole genome, the amount of detected methylation loci coming from the paternal genome is equal to the maternal genome, but it does not accord with 1:1 for each linkage group. In order to identify the relationship between methylation loci and some key agronomy traits, we carried out single marker analysis. The number of methylation loci significantly related with each trait is different. Seed quality traits are more effective with DNA methylation than traits related to plant growing and developing, and the least effective traits are yield related. The most related trait is seed developing period with which there are 68 methylation loci significantly related, 1.7 times of the average value. The least related trait is seed production with only 17 loci, not more than half of the average amount.