Study On Genomic DNA Methylation Variation Induced By Rye-wheat Chromosome Translocation

In wheat breeding,through chromosomal translocation and other means,excellent germplasm resources of various wheat relatives including rye have been introduced into wheat,and a large number of new wheat varieties(or lines)have been cultivated.Some of these materials have new traits that neither parents have.For the generation of these new traits,it seems that it is far from enough to explain the genetic effects of the foreign germplasm in the wheat genome.The researchers believe that epigenetics may provide new research ideas to explain this new trait.The resulting genetic evolution mechanism.In this paper,the wheat-rye primary translocation line and its parent material are used as the research object.Based on the analysis of the genetic stability of the wheat-rye translocation line using the AFLP molecular marker technology,the CCGG locus is re-used by MSAP The methylation status was analyzed.By comparing the methylation polymorphism between sister translocation lines,different monomer addition lines,different donor-receptor combinations,and between translocation lines and corresponding parental materials,explore the receptor genomic DNA caused by the introduction of foreign chromosomes into wheat The law of methylation level and pattern variation.At the same time,the creation process of the primary translocation line materials used in this experiment simulates the process of distant hybridization of plants and their subsequent polyploidization.Therefore,this set of materials was used to explore the DNA methylation level and the effect of model variation on plant evolution.This study mainly achieved the following results:1.AFLP electrophoretic pattern polymorphism of wheat genomic DNAUsing AFLP molecular marker technology,127 wheat-rye primary translocation lines bred with MY11 and A42912 as wheat parents,Weining rye,dwarf rye,and white grain rye as rye male parents,respectively.Genomic DNA was tested.The results showed that the consistency of the amplified bands between the sister translocation lines was extremely high,and the mutation rate of the amplified transgenic lines was very low compared with the parent amplified bands.This shows that although the introduction of foreign germplasm may cause changes in the wheat chromosome at the nucleotide sequence level,this change is small.It proves that the detected wheat-rye translocation line is relatively stable genetically at the molecular level.2.Polymorphism and overall trend of wheat genomic DNA methylation levelThe experiment used EcoR Ⅰ and Hpa Ⅱ/Msp Ⅰ double digestion modification to be suitable for the “methylation sensitive amplification polymorphism” analysis system of wheat genome,and detected 129 material methylation modification sites at the whole genome level.The results showed that the half methylation rate,total methylation rate,and overall methylation rate of the parent MY11 were 20%,12.73%,and 32.73%,respectively;3.The overall methylation rates are 3.92%-40.61%,8.48%-33.33%,17.65%-56.97%;the parent A42912’s hemimethylation rate,total methylation rate,and overall methylation rate are 20.26,respectively.%,15.03%,35.29%;the half-methylation rate,total methylation rate,and overall methylation rate of breeding translocation lines are 16.99%-38.56%,8.50%-25.49%,33.99%-56.86%,respectively..From the above results,it can be seen that the introduction of exogenous germplasm has caused significant changes in the methylation levels of the three forms of DNA in the receptor genome,and is developing toward a trend of increased m ethylation.3.Polymorphism and overall trend of methylation pattern of wheat genomic DNAThrough one-to-one comparison of the methylation status of the selected translocation line and the parent at 165 sites,we found that the MY11 selected translocation line was among the 165 sites: 9.00%-96.00% of the sites showed that the parent showed Consistency,demethylation variation occurred in 0.00%-26.32% of sites;hypomethylation occurred in 0.00%-77.00% of sites;hypermethyl occurred in 0.00%-60.00% of sites Change.From the frequency of three types of mutations in 100 MY11 breeding translocation lines,we can see that the methylation pattern mutations after the introduction of foreign chromosomes are rich in polymorphism.Further analysis revealed that after the introduction of exogenous chromosomes,the methylation state transition is more likely to increase the overall methylation level through the type of mutation of hypermethylation.4.Wheat genomic DNA methylation level and source of model variationThe formation of translocation lines can be roughly divided into three processes:distant hybridization,monomer addition line formation,and chromosomal translocation events.Through experimental design,explore whether the above-mentioned methylation variation is formed in that process.The results showed that different donoracceptor combinations produced significant differences in methylation level and pattern variation during distant hybridization;there was no significant difference in DNA methylation level and pattern during the formation of monomeric additional lines;In the process of chromosomal translocation events,the methylation level and pattern have undergone extremely drastic changes.5.Mutual conversion of methylation status of wheat genomic DNABy comparing the parent with a total of 16215 bands,we found that the three methylation states(unmethylated,hemimethylated,and fully methylated)can be converted between each other,specifically: unmethylated The state is converted to hemimethylation and permethylation through hypermethylation variation;reversible processes can also occur through demethylation;at the same time,hemimethylation and permethylation can also be switched between each other through hypomethylation.Although these three methylated states can be converted to each other,the frequency of the various conversions varies greatly.In general,the unmethylated state is easier to transition to hemimethylation and permethylation The frequency of occurrence is 13.08%and 8.31% respectively;the frequency of occurrence of permethylation to hemimethylation is very low,only 0.71%.In summary,the methylation state changes dynamically.It is precisely because of this rich and flexible state transition that methylation has its unique function and significance for plants to quickly adapt to the environment.