Genome DNA Methylation of Natural and Artificial Polyploids in Citrus grandis

摘要

DNA methylation plays an important role in gene expression regulation during growth and development of plant. Study on the genome DNA methylation pattern of twelve natural and artificial tetraploid strains, one natural triploid strain and their diploid maternal parent in Citrus grandis was carried out by methylation sensitive amplified polymorphism (MSAP) technique. The results showed that: (1) In fourteen strains 9 688 bands including 2 368 methylation bands and 1 369 full methylation bands were amplified in total, and the polymorphic proportion was 24.4%. (2)The total methylation ratios in tetraploids were 21. 6% -25. 8% , with an average of 23. 8% ; the full methylation ratios were 11.4% - 14.8%, average on 13.9%. Compared with the methylation ratios (26.0%) and full methylation ratios (16. 9%)of maternal parent, both were lower in the tetraploids, while the natural and artificial tetraploids showed little difference on methylation level. The methylation ratio of the natural triploid was 26. 0% and the full methylation ratio was 15.1% , compared with the maternal parent, the methylation ratio was uniform and the full methylaiton ratio decreased about 1. 8%. (3) Compared with the maternal parent, there were 14 types of methylaiton patterns existed of these ployploids. They were classified as four categories; pattern A, monomorphism, there were 1 284 loci in all tetraploids and the occurrence frequency was 35.7%, which in natural triploid were 119 and 40.8%; pattern B, demethylation, which existed on 889 loci in all tetraploids and occurrence frequency was 24.7% , in triploid were 76 and 26. 0% ; pattern C, hypermethylation, there were 990 loci in all tetraploids and occurrence frequency was 27.5%, in triploid were 59% and 20.2%; pattern D, hypomethylation, which loci were 437 in all tetraploids and occurrence frequency was 12. 1% , in triploid were 38 and 13.0%. In conclusion, the tendency of methylation level change was not obvious in the process of polyploidization, but methylation patterns changed and readjusted that demethylation and hypermethylation were the most due to the polyploidization in Citrus grandis.