Phenotypic Plasticity And The Molecular Mechanisms Of Leymus Chinensis In Heterogeneous Soil Habitats In The Songnen Plain

Phenotypic plasticity refers to the phenomenon that organisms produce multiple phenotypes in response to environmental changes or heterogeneity with the absence of genetic variation.It is widespread in animals,plants and microbes.Unlike animals that can escape from unfavorable habitats,plastic phenotypic variation is particularly of great adaptive importance to immobilized plants.Leymus chinensis is a polyploid grass that is widely distributed in Eurasia continent and propagates mainly through clonal rhizomatous elongation.The species is well-known for the remarkable ecological adaptability,it is tolerant to a wide range of ecological factors including drought,cold,salinity-alkalinity and grazing.Previous studies suggest L.chinensis manifests great phenotypic plasticity when confront with different selective pressures which is possibly one of the rationales for the plant adaptability.Nevertheless,further molecular mechanism underlying the phenotypic plasticity is relatively lack.In this study,by planting clonal plants of L.chinensis into four different types of soil(i.e.,farmland,forest,salinity-alkalinity and sand)collected from Songnen plain,we measured the phenotypic changes and built the connection between different phenotypic indices with soil chemical factors.Most importantly,de novo RNA-seq was involved to globally analyze the differentially expressed genes(DEGs)induced by different soil conditions,we found the major conclusions are as follows:Firstly,the four soils caused distinct phenotypes in L.chinensis plants with respect to a variety of morphological and physiological parameters.The plans grown in farmland soil exhibited the most vigorous growth status.The total biomass,plant height,leaf morphology and rhizomatous length treated by farmland soil were all significantly higher than that in the other three groups.The highest photosynthetic rate was discovered in the plants grown in forest soil.In contrast,the saline-alkalinity and sand soil can be regarded as salt and drought stresses as the result of the high pH and low water content in the two soils respectively.The highest meanwhile exceptionally attenuated data distribution of soluble sugar content was found in the former.In the latter,the largest root-shoot ratio and highest number of spikelets were obtained.All of the morphological and physiological variation are the signs of adaptive responsiveness in L.chinensis coping with different soil conditions.Secondly,further environment-phenotype association analysis revealed that there was a close connection between phenotypic characteristics of L.chinensis with corresponding soil properties.The abundant nutrients in farmland soil such as total carbon and nitrogen were the main reasons for the vigorous growth of plants;while the highest nitrate nitrogen content in forest soil significantly explained the enhanced photosynthetic rate.In contrast,the pH,Na~+,ammonium nitrogen and water content were the main factors that affected the morphology and physiology of L.chinensis under the two adversary soil conditions.Thirdly,the comparative transcriptomic analysis suggested that differentially expressed genes(DEGs)induced by the four soils were enriched in different metabolic pathways according to KEGG database.The pathways including plant hormone signal transduction,synthesis of zeatin,fatty acids,phenylalanine glutathione,etc.,were closely related to plant growth.Moreover,both the regulatory and functional protein synthesis pathways play important roles in improving plant tolerance to stress conditions.The further analysis of gene activation and silencing by gene ontology(GO)suggested the groups of genes were classified into GO terms such as response to stimulus,reproduction and developmental process.These results are in correspondence with the phenotypic and ecological results and provide molecular evidence for phenotypic variation in L.chinensis.At last,no matter for the analysis of DEGs or gene activation/silencing,only few genes were intercrossed between the different groups of treatment suggesting the transcriptomic expression in L.chinensis were highly condition-dependent,in other words,specific genes can be invoked to deal with the impacts generated from different soils.This result reflects the transcriptome of L.chinensis are flexible so as to improve adaptability to different soil conditions.To sum up,L.chinensis can rapidly change phenotype in order to deal with the impacts of environmental heterogeneity even no genetic accumulation yet accumulated.The ability to adjust phenotype of L.chinensis is possibly rooted in the evolved intrinsic property of specifying transcriptome profiles in response to diverse soil conditions.