Analysis of methylation-sensitive amplified polymorphism in different cotton accessions under salt stress based on capillary electrophoresis

A methylation-sensitive amplification polymorphism method based on capillary electrophoresis was used to analyze DNA methylation levels in three cotton accessions, two salt-tolerant accessions CCRI 35 and Zhong 07 and one salt-sensitive accession CCRI 12. Many categories of DNA methylation happened in the three cotton accessions under salt treatment, including hypermethylation, hypomethylation, and other patterns. Hypermethylation happened at a significantly higher rate than that of hypomethylation in salt-tolerant accessions CCRI 35 and Zhong 07. On the contrary, in salt-sensitive accession CCRI 12, hypomethylation happened at a significantly higher rate than that of hypermethylation. In general, the global DNA methylation level significantly increased under salt stress in both salt-tolerant accessions CCRI 35 and Zhong 07, whereas there was no significant difference in the salt-sensitive accessions CCRI 12. Our results suggested that salt-tolerant cotton might have a mechanism of increasing the methylation level when responding to salt stress; the increase of the global level of DNA methylation and also different methylation patterns might play important roles in tolerance to salt stress in cotton. Some interesting genes were found through cloning and analysis of differently methylated DNA sequences, which might contribute to salt tolerance in cotton.