The Effects Of ABA Or SA Pretreatment On The Total Level Of DNA Methylation Under Water And Salt Stress

Drought and salt are very important factors of environmental stress. Because of the greatdamages to the production in agriculture, researchers attach importance to the effects ondrought and salt stress. The sdudy is about determination on total level of DNA methylationof leaf in rice seedlings. And the pretreatment with abscisic acid (ABA) and salicylic acid(SA) was used to study the change regulation of DNA methylation under the drought or saltstress in rice.The results were as follows:This study examined the critical methodological factors in the HPLC analysis of DNAmethylation. It included DNA extraction and HPLC conditions choice. The experimentalresults showed that CTAB I was superior to CTAB II. The better HPLC conditions wereDiamonsil C18(2)(250mm×4.6mm,5μm) column, mobile phase consisting of methanol-KH2PO4(10mmol/L)(10:90, V/V) at a flow rate of0.5ml/min, the column temperature35℃, pH3.5and the detection wavelength285nm. With the optimized method of DNAextraction and HPLC conditions, the better result was achieved in the chromatogram ofcytosine(C) and5-mC (5-methylation cytosine) in genomic DNA hydrolyzate.Compared to the control, the total level of DNA methylation with pre-treatment in riceleaf was increased. The result showed that adversity stress contributed to the increasing of thelevel on DNA methylation.Total level of DNA methylation all increased in groups with ABA pretreatment, SApretreatment and control under water stress. From0h to4h, the groups with SA pretreatmentand control reach the highest level, the group for ABA pretreatment only close to the highestlevel.From4h to24h, the group for ABA pretreatment reached the highest level, however,the groups with SA pretreatment and control reduced slowly. From24h to144h, the controlgroup raised as well while the ABA pretreatment and SA pretreament groups decreasedslowly. In conclusion, ABA pretreatment and SA pretreatment all remitted the increasingtendency of the total level on DNA methylation.Total level of DNA methylation all increased in groups with ABA pretreatment,SApretreatment and control under salt stress. Though the three groups could not reach thehighest, from0h to4h, they all increased to some extent. The DNA methylation levelreached the highest from4h to24h in ABA pretreatment and control groups,but the SA pretreatment was not yet at the highest level. From24h to144h, the ABA-pretreatment andcontrol groups all tasked back, but the SA-pretreatment group continued increasing just onlywith a little extent. In any case, ABA-pretreatment group still reduced the tendency ofincreasing in DNA methylation. However, on the contrary, SA-pretreatment increased thelevel of DNA methylation.