Study On The Suitable Area Of Wedelia Trilobata And Its DNA Methylation Characteristics In Heterogeneous Environment

In the past few decades,the scale of the biological invasion has entered a new stage,and alien invasive plants have seriously threatened the safety of local ecosystem.Wedelia trilobata was the common invasive plant in South China,and it also had strong environmental adaptability.Because W.trilobata mainly reproduced by cloning,the gene flow between individuals was restricted,which reduced genetic variation,so the epigenetic mechanisms may play an important role in it adapation to heterogeneous environment.In this study,based on MaxEnt model,the distribution of W.trilobata in China was predicted,and the methylation sensitive amplified polymorphism(MSAP)was used to analyze and compare the DNA methylation characteristics of W.trilobata from different invasion areas,and to explore the relationship between the methylation variation and environmental adaptation of W.trilobata in different regions.Meanwhile,combined with the method of environmental control experiment,the DNA methylation level and variation pattern of the W.trilobata under temperature stress were examined,and the differential MSAP bands of W.trilobata were analyzed preliminarily.The main results were as follows:1.The potential suitable area of W.trilobata in China was predicted based on Max Ent model.The area under the receiver operating characteristic curve(AUC)values were above 0.9,which indicated the high prediction accuracy.Among the 19environmental factors,the top four with the highest contribution rate were the precipitation of the warmest quarter(bio 18),precipitation of the wettest month(bio13),precipitation of the driest month(bio 14)and precipitation of the wettest quarter(bio 16),which suggested that precipitation was the dominant factor affecting the distribution of W.trilobata.The model predicted that the potential suitable area of W.trilobata was 218,500 km~2,suitable area in 22 provinces and regions.The best suitable area of W.trilobata was 66,000 km~2,which was basically consistent with its current suitable area.With the climate change in future,the total suitable area for W.trilobata in China will remain about the same,while the suitable area pattern changed.The best suitable area descresed,but the medium and high suitable area increased.The best suitable area tended to spread towards southwest China,especialy in Guizhou province.2.Eight pairs of primers were selected for MSAP analysis of 60 W.trilobata individuals from Fuzhou,Haikou,Jinghong and Guangzhou population.A total of14520 loci were amplified.The average total methylation rate was 46.60%.At the species level,Nei’s gene diversity(H)and Shannon diversity information index(I)were 0.2814 and 0.4401,respectively,which indicated that W.trilobata had high epigenetic variation.The percentages of polymorphic loci of W.trilobata were60.33%～100.00%.Genetic differentiation coefficient of population(Gst)was 0.3448,and gene flow(Nm)was 0.9499.The aboved results showed that the gene flow was restricted,and there existed genetic variation between different W.trilobata populations.In addition,the significant correlation between epigenetic diversity of W.trilobata and environmental factors was found,and the hemi-methylated rate was significantly correlated with altitude.These results suggested that the methylation variation of W.trilobata in different regions was affected by environmental factors,which may be related to its adaptation to heterogeneous environment.3.Temperature stress increased the methylation level of W.trilobata to different degrees.After high temperature stress,total methylation rate of W.trilobata and native W.chinesis increased by 2.24%、2.43%respectively and 28.43%and 32.78%of methylation loci in these two species were mutated.Methylation and demethylation were both involved in their response to high temperatures.After low temperature stress,the total methylation rate of W.trilobata increased by 7.65%,which was significantly greater than that of W.chinesis(1.16%).Demethylation or methylation variation occurred at 43.91%and 30.64%of methylation loci respectively,among them were dominated by methylation.Temperature stress induced the methylation variation in both W.trilobata and W.chinesis,and increased,the methylation levels,which indicated that DNA methylation was involved in their responses to temperature stress.The specific MSAP fragments expressed under high temperature stress in W.trilobata were recovered and sequenced.Due to short sequences and no reference genome,functional segments with high similarity have not been aligned.