Study On Genome DNA Methylation Between The Special Haploid And Progeny In Twin-seedling Rice

DNA methylation,which consist in much propagation,is an significant epigenetic modification.It plays an important role in gene expression and regulation,plant cell differentiation,genomic imprinting and phylogeny.According to many researches,the variation of DNA methylation can be transferred to the offspring by cell division.To date, the research methods on DNA methylation can be classified into three types:genome-wide methylation analysis,gene-specific methylation analysis and newly methylated sites screening.The technique of methylation-sensitive amplified polymorphism(MSAP) can be used for DNA methylation analysis of 5′-CpCpGpG site.Zhang Hongyu and Peng Hai used this method to research the haploid,diploid and triploid which come from the same twin-seedling rice.They found that epigenetic modification plays an important role in the haploid,diploid and triploid.They also found that the methylation levels and pattern of the haploid,diploids and triploid were different.The DNA cytosine methylation mutation at the 5′-CpCpGpG sites of haploid,Shuhui 527(R527),Shuhui 363(R363) and their hybrids were studied with MSAP.It can help us understanding the regulation mechanism of the haploid epigenetic.The main results were as follows:1.The average MSAP ratio(the ratio of total methylated sites to total detected sites ) of the hybrid F₁(haploid×R527 ) was 46.63%,the ratio of full methylation(double strands CmCGG ) was 45.92%.The two ratios were lower than that of the male parent R527(50.60%,49.40%),but higher than that of the female parent Haploid(42.08%, 40.98%).And the average MSAP ratio of the hybrid F₁′(haploid×R363 ) was 41.06%, the ratio of full methylation was 39.38%.The result was opposite to that of F₁,the two ratios were lower than that of the female(42.08%,40.98%),but higher than that of the male (40.57%,39.43%).And the variation range was small.2.Compared to the hybrid F₁,F₁′and their parent,there would be five mehtylation mutation pattems:Type A,same methylation pattern between hybrid and their parent;Type B,demethylation;Type C,hypermethylation;Type D,hypomethylation;Type E,uncertain type.3.While hybridization,the methylation pattems in F₁,F₁′were changed greatly to coordinate the expressions of genes from two heterogeneous parents.Some genes transcribed with high efficiency,but others were inhibited.The methylation level of hybrid was higher than the female and lower than the male,or otherwise.It might be because of the readjustment of methylation level and pattern in hybrid progeny,which can regulate the gene expression and make the adaption to the environment of the hybrid progeny become easy.4.Because the two hybrids have the same female parent--the haploid,by comparing F₁,F₁′with their parent,we can winkle the different band which resulted from environment and individual,we can also know the haploid DNA methylation sites which were different from parent.The sites have two types:(1) the special methylation sites of the haploid;(2) the methylation sites which come from the haploid only.