Research On The Formation Of Short-term Drought "memory" In Plants Involved In DNA Methylation

Improving the plant capacity to cope with abiotic stress is a hot area of molecular biology.Stress memory as an important mechanism to cope with abiotic stress has been paying close attention by research workers in recent years.Epigenetic factors play a key role in the formation of memory.For example,high H3K4me3 level in promoter region can facilitate the expression of ?1-pyrroline-5-carboxylate synthetase 1(P5CS1),and then facilitate formation of salt memory in Arabidopsis.However,it remains unknown whether DNA methylation is involved in the manifestation of drought memory,especially short-time drought memory.Physcomitrella patens,as one of the bryophytes,has been considered as the model plant because of its high homologous recombination frequency,short vegetative cycle and simple nutrients they required.Moreover Physcomitrella patens is an ideal plant for the study of drought memory because its powerful capacity to rehydration.It has a great-applied value that analysising drought memory in rice(Oryza Sativa)which is the major crop plants in China.In this study,the patterns and level of DNA methylation was investigated using Bisulfite sequencing technique in rice and Physcomitrella patens,respectively;and the potential function of DNA methylation underlying drought memory formation was uncovered.Main results and conclusions are summarized as following:1.In rice,we found that the CG methylation was the main sequence contexts,following the CHG and CHH.Most of CG sequence context were heavily methylated,while CHH sequence context showed hypomethylation in genome.Interestingly,the CHH methylation was largely changed under drought stress.Instead,the CHH sequence contexts DNA methylation is the main parts in Physcomitrella patens.2.Most of the DMRs(differentially methylated regions)that have certain changed trends in first drought stress showed difference changed trends in forth drought stress.The CG and CHG methylation can repress gene expression in rice gene flanking region and the same function of CHG and CHH type methylation in rice gene gene body region.However,there is no correlation between DNA methylation change and gene expression change.3.We found a significant change of DNA methylation in most of “memory” genes.DNA methylation participates in drought memory formation through regulating genes that involved in biosynthesis of Stilbenoid,gingerol and amino acid and metabolites of alpha-Linolenic,Linoleic acid,Cysteine and methionine.A small part of “Memory” DMR moderates “Memory” gene to participate in the biosynthesis of Phenylpropanoid,Sesquiterpenoid,triterpenoid,Carotenoid and wax and metabolism of arginine and proline.