The Global DNA Methylation Of Pyropia Haitanensis Under High Temperature Stress

Pyropia haitanensis is widely cultivated in the southern China coast,and represents 75%of the total production of cultivated Pyropia in China.Over the past several years,the continuous high temperature weather under the background of global warming has markedly affected the cultivation of P.haitanensis and significantly reduced its yield.To address this problem,several high temperature-tolerant strains of P.haitanensis have been selected,the mechanisms of response to high temperature were studied,significant upregulations were found on genes encode methyltransferases and glycosylases in high temperature-tolerant of P.haitanensis when exposure to high temperature.These results indicated that DNA methylation plays an important role in the adaptation of P.haitanensis to high temperature stress.In the present study,the potential contributions of DNA methylation-mediated gene regulation in a high temperature-tolerant strain of Pyropia haitanensis?Z-61?were investigated by using the methylation-sensitive amplification polymorphism assay.The main results are as follows:1.A significant association between the high temperature stress and the level of methylation was observed.The content of global ^5-mC in Z-61 was significantly decreased by high temperature which was confirmed by the MSAP results.In the present study,55 polymorphic bands between the control and high temperature stress-exposed?two different exposure times?thalli were randomly selected and sequenced.2.Further analyses found that methylated sites of 29 fragments were located within the coding regions,whereas the others were positioned within noncoding regions or promoters.BLASTN analysis indicated that the 29 fragments are homologous to those involved in numerous processes,including abiotic stress response,programmed cell death,photosynthesis,energy metabolism,signal transduction,protein synthesis,and transposon activation.3.Among these 29 MSAP fragments,18 fragments were highly expressed,as indicated by the results of RNA-seq,whereas the remaining 11 genes exhibited either very low or no expression at any time point under exposure of high temperature stress.Eight genes?includes 5demethylated genes and 3 methylated genes?were choosed for examination of the qRT-PCR analysis from the 18 fragments,we observed that MSAP methylation status of genes were highly correlated with their expression.4.The methylation of P.haitanensis thalli were decreased by treat of demethylation reagent5-azaC.Although the photosynthesis still decreased by high temperature,but addition of 5-azaC could enhanve the ability of photoprotection.The cytological observation further supported that the addition of 5-azaC improved the tolerance of Z-61 to high temperatures.