| Intrinsic DNA methylation pattern is an integral component of the epigenetic network in many eukaryotes. DNA methylation is known to play an important role in the regulation of gene expression in eukaryotes. Biological stress for the plant will provide an inherent epigenetic driving force of evolution. Research DNA methylation patterns with certain conditions will help us fully understand the epigenetic regulation of gene expression and DNA methylation of biological functions. The wheat near-isogenic line TcLr19, TcLr41 and Thatcher are race-specific resistance and susceptible in the interaction with the race THTT of puccinia triticina respectively, they are special materials.Using methylation-sensitive amplified polymorphism (MSAP) analysis, the patterns of cytosine methylation in TcLr19 and Thatcher that had been inoculated with puccinia triticina, subjected to left untreated were compared. Totally 3554 DNA fragments, each representing a recognition site cleaved by either or both of two isoschizomers, were amplified using 60 pairs of selective primers. A total of 998 sites were found to be one of the methylated. The results suggest that no differences in cytosine methylation exist between seedlings inoculated and those unchallenged. We selected 12 pairs of selective primers from 60 pairs, to compare the patterns of cytosine methylation in TcLr41 and Thatcher that had been inoculated with the race TKTJ of puccinia triticina, subjected to left untreated. In all, 934 DNA bands were amplified by 12 pairs of selective primers. A total of 239 sites were found to be one of the methylated. The results suggest that no differences in cytosine methylation exist between seedlings inoculated and those unchallenged with Puccinia triticina. No significant differences were detected in both compatible and incompatible interactions, but DNA methylation changes between Thatcher and TcLr41 had no relation with pathogen were found. Tatcher DNA can be digested with EcoR I-Hpa II and EcoR I - Msp I respectively. TcLr41 DNA can be digested with EcoR I-Hpa II, however, It can not be digested with EcoR I-MspI. The results indicated that those sites are hemi-methylated. Some DNAmethylation changes existing between seedlings inoculated and those unchallenged were found too. But those changes were not reduplicative in independent amplification. However this polymorphism can be detected from as many as 21 pairs of primers, the differences in the detection rate is as high as 35%. The existence of this phenomenon in many other crops MSAP analysis has not been reported.The wheat MET1 fragment was also cloned and sequenced. The Blastn analysis showed that it had 87% homology with Oryza sativa (japonica cultivar-group) putative cytosine-5 DNA methyltransferase (MET1-2) gene.The epigenetic stability of the whole wheat genome was studied using 60 pairs of primers and three wheat materials. The results suggest that there was no significant difference between the challenged and unchalleged plants. However, some instabale and seemingly random methylation changes were found, and epigenetic differences between the near-isogenic lines for wheat leaf rust resistance genes were also present. |
