Characterization Of DNA Methyltransferase And Demethylase Genes In Fragaria Vesca

DNA methylation is one of the important epigenetic modifications in plant.At present,it has been found that DNA methylation are closely related with plant growth and development,plant morphogenesis and other aspects,but it’s impact on fruit development,especially on non-climacteric fruits’ development are with little research.In this study,We firstly identified the DNA methylation modifiers in Fragaria vesca and many other species,We found that 9 genes contained DNA methylase domain(include 8 DNA methylase genes and 1 tRNA methylase gene),and 4 DNA demethylase genes in Fragaria vesca.Then we conducted a series of phylogenetic analysis,referring domain structure,motif structure,exon structure and so on,the classification of different families in our study are consistent with previous results.Fragaria vesca have four methylase families,including 3 DNA methylases in CMT3 family,1 DNA methylase in MET1 family,4 DNA methylases in DRM1/2 family and 1 tRNA methylase in DNMT2 family.DNA demethylase have two families,including 1DNA demethylase belongs to DME family and 3 in DML(ROS1、DML2、DML3).Previous studies shown that Fragaria vesca haven’t occurred apparent duplication events after it diverged from Rosaceae,and our Mcscan results also indicate that Fragaria vesca haven’t whole-genome duplication events and Tandem duplication events recently.Our study also analyzed the distribution of DNA methylation modifiers in other several horticultural plants,It is worth noting that,DME family only found in dicots,but in Amborella trichopoda,Oryza saliva and Zea mays.The diploid woodland strawberry Fragaria vesca is a typical non-climacteric fruit crop.To realize the relationships between DNA methylation and non-climacteric fruit ripening,our study selected five critical periods during strawberry fruit ripening(Big green fruit,Little white fruit,Pre-turning fruit,Pink fruit,Red fruit),then detected the expression levels of these DNA methylation modifiers by RT-qPCR.We found that many DNA methylase and demethylase genes reach their highest expression levels before or after the strawberry fleshy fruits turning from white to red,suggesting that DNA methylation might undergo a dramatic change at the onset of leshy fruit-ripening process.Furthermore,Strawberries are forest herbs in nature,they are easy to suffer different adverse impacts of the environment.To explore the roles of DNA methylation modifiers plays on Strawberry under abiotic stress,we select four severe abiotic stresses(drought,salinity,cold,heat)to further study.According to the RT-qPCR results,we observed that the expression of many DNA demethylase genes increased in response to these abiotic stresses,but they all belong to DML family,while the expression levels of DME family genes have not significantly change,which reason maybe that DML family mainly take part in the process of vegetative growth,but DME mainly related to reproductive growth process.Collectively,our study investigated 8 DNA methylase genes in Fragaria vesca,most of them reach their highest expression levels before or after the strawberry fleshy fruits turning from white to red,and 2 out of 4 DNA demethylase genes reach their highest levels in this stage.These results reveal that DNA methylation maybe play important roles in non-climacteric fruit(strawberry)ripening process,and maybe of vital important about the growth of strawberries under abiotic stress.We believe that our work presented some ideas on the possible roles of DNA methylation during non-climacteric fruit ripening stages,and give some basis for the further studies about the roles of DNA methylation in abiotic stress environments.