Study on DNA Cytosine Methylation of Cotton (Gossypium hirsutum L.) Genome and Its Implication for Salt Tolerance

To study the relations between DNA methylation and abiotic stress responses in cotton (Gossypium hirsutum L.), the methylation-sensitive amplified polymorphism (MSAP) method was used to investigate the differences in methylation level and the change of cytosine methylation patterns under salt (NaCl) stress in two different salt-tolerant cotton lines. The results showed that the number of the cytosine methylation of CCGG sites in high salt-tolerant cotton line was less than that in low salt-tolerant line. Under salt stress, extensive cytosine methylation alterations including hypermethylation and demethylation as well as the potential conversion of methylation types occurred in the salt-treated cotton line compared with the corresponding control. Interestingly, salt stress-induced demethylation loci that occurred in high salt-tolerant cotton line were greater than those in low salt-tolerant cotton line, however, salt stress-induced hypermethylation loci in the high salt-tolerant cotton line were less than those in low salt-tolerant cotton line. It suggested that the demethylation positively contributed to salt tolerance and the hypermethylation had negative effect on salt tolerance in cotton.