The Effect Of Parental Environment On Habitat Selection Strategies And Epigenetic Memory Regulation Of Clonal Plant

Clonal plants in heterogeneous environments can benefit from their habitat selection behavior,which enables them to utilize patchily-distributed resources efficiently and enhance their competitiveness.Therefore,studies on habitat selection of clonal plants in heterogeneous environments have attracted much attention.It has been shown that the habitat selection of plants can be strongly influenced by their memories on past environmental interactions.Environmental stress can be remembered by plants in a form of ‘stress memory'.In some cases,such a memory can alter phenotypes of their descendants.Epigenetic variation was proposed to be one of the mechanisms involved in the memory.In this study,we used G.longituba and T.repens as experimental materials,and set up ultraviolet-B(Ultraviolet-B,UV-B)radiation environment and drought stress environment respectively.Using clonal plant G.longituba in UV-B radiation environment,the growth indicators(biomass,number of ramets,leaf area,stolon length,specific leaf area,specific stolon length,growth direction)and DNA methylation of the ramets(parental ramets,older offspring ramets,and younger offspring ramets)were analyzed to discussed whether the UV-B radiation of the parental environmental of clonal plants G.longituba triggers the epigenetic memory.Whether epigenetic memory is transmitted across generations and affects the habitat selection behavior of the clonal offspring in a heterogeneous UV-B radiation environment.We further explored the impact of different UV-B radiation intensities of parents on the clonal plant habitat selection strategy.In addition,under drought stress environment,we use clonal plants T.repens,induce parental ramet produce drought stress memory and maintain different time,phenotypic index(biomass,stolon length,the number of nodes,the number of branch and growth rate)of offspring ramets in different parental memory time were analyzed to discussed how long the memory is kept by plants.The main result as below:(1)Direct UV-B radiation significantly reduces the biomass and the ramets number of offspring of the parental ramets,Its offspring ramets are prefer to grow in habitats with good light environment rather than in UV-B radiation environment,which is manifestation of “escape strategy”.Offspring of control parental ramets show similar preference to the two light environments(Control light environment and UV-B radiation environment).Parental ramets exposed to direct UV-B environment reduce the level of overall DNA methylation and epigenetic diversity.The methylation of UV-B-stressed parental ramets was maintained among their offspring ramets,although the epigenetic differentiation was reduced after several asexual generations.(2)The different UV-B radiation doses of the parental ramets obviously lead to different habitat selection strategies of their offspring in the heterogeneous environment.Parental UV-B radiation experience reduce the stolon length of their offspring,and the degree of reduction is related to the UV-B radiation dose.Epigenetic changes mediated by DNA methylation affect the stolon length of the offspring before bending.When the parents were in adjust UV-B dose,it increases the maximum net photosynthetic rate and the content of UV-absorbing compounds to resist ultraviolet radiation,the stolon length of the offspring selected to grow in different habitats did not show significant differences;and when the parent plant under stress UV-B dose,it forms smaller and thicker leaves,shortening the petiole length to avoid stressing UV-B radiation,the offspring shown significant differences in habitat selection,which increase the stolon length of the offspring selected to grow in the stress UV-B environment and shown as an "escape strategy" for expansion and growth,while the stolon length of the offspring selected to grown in the control light environment did not change significantly.(3)We found that the drought stress experienced by parental ramet affected phenotypes of their offspring ramets.for example,such a memory resulted in enhanced the side branches number of offspring originating from parental ramets that experienced drought stress.This Transgenerational effect of the parental environment is mediated by epigenetic changes mediated by DNA methylation.The drought stress memory of parents can be passed on to offspring across generations,but the memory was time limited and was gradually erased.We did not find any transgenerational memory in offspring of plants that experienced drought stress later than 6 weeks before their transplantation.Therefore,drought-induced drought stress memory can be maintained in the parents for a period of time and then disappear.Moreover,these changes show differences in genotypes.In conclusion,we provide evidence that the growth behavior of clonal plants is obviously affected by the environment experienced by their parents.This maternal effect can be transmitted to the offspring ramets across generations through epigenetic changes mediated by DNA methylation,then affect the phenotype,physiology and growth behavior of the offspring.Besides,epigenetic memory was also affected by stress intensity and time dynamics.Memory is time-effective and will gradually weaken in the process of trans-generation.This will contribute to a deeper and comprehensive understanding of the plant behavior and its mechanisms.