Tissue Specific DNA Methylation And Infraspecific (Gossypium Barbadense) Methylation Polymorphism Analysis In Cotton

DNA cytosine methylation is an important epigenetic phenomena in cotton development and tissue differentiation,materials of different origin or tissues from the same material could regulate gene expression by changing their DNA methylation pattern.Here,by using the method of methylation-sensitive amplified polymorphism (MSAP),cytosine methylation in the site of 5′-CCGG-3′was analyzed within four different tissues(young leaf,old leaf,bract and fiber) from Pima 3-79 and Emian 22. Methylation difference was explored among Gossypium hirsutum.Gossypium barbadense and their hybrid.Also DNA methylation polymorphism cluster was firstly constructed to compare with earlier obtained SRAP cluster.Results revealed in the following:1.Tissue specific methylation analysis was conduct to obtain 5321 clear bands by using 88 primer combinations,663(12.5%) bands of them exhibit methylation in either Pima 3-79 or Emian 22,Of the obtained 663 bands,Emian 22 had 618(93.3%) bands with the same methylation pattern and 45(6.7%) bands with tissue specific methylation pattern,also Pima 3-79 had 616(92.9%) bands with the same methylation pattern and 47(7.1%)with tissue specific methylation pattern,which indicated low tissue specific methylation in cotton.2.Compared with its parents,hybrid showed extensive cytosine methylation alterations including hyper-and de-methylation as well as the potential conversion of methylation types(from external cytosine to internal cytosine or vice visa). Hyper-methylation loci(69.3%) were much more than de-methylation loci(6.1%).3.One hundred and seventeen methylation loci were obtained in methylation polymorphism analysis,and 31(26.5%) of them were polymorphism.Using the date of 24 methylation polymorphism loci with high confidence and repeatability to cluster 28 cotton materials,results showed that Gossypium hirsutum,Gossypium barbadense and their hybrid were perfectly separated.The average Jaccard coefficient of 25 Gossypium barbadense in Methylation polymorphism dendrogram (0.67) was much higher than in SRAP sequence polymorphism dendrogram(0.48), indicated methylation polymorphism was less than sequence polymorphism. Pima3-79,Pima90,Bimamianl and Sudan2B were discovered to cluster in both dendrograms,But for other Gossypium barbadenses studied,no evident relationships between the two clusters were revealed.4.Seven mehtylation loci were sequenced and 5 were similar to existing functional gene sequences(Gossypium raimondii transposon Mutator-like,cytochrome oxidase or RecA) in public databases,other 2 sequences were severely similar to sequences reported by Zhao et al.,(2008) without function announceed.