Ecological Adaptability And Response Mechanism To Salt Stress Of Wild Apocynum Venetum

Apocynum venetum L.is a perennial semi-shrub root plant with important medicinal,ecological and economic values.And it is a valuable wild plant germplasm resource in China.At present,the wild population of A.venetum is shrinking.Xinjiang and Inner Mongolia,where A.venetum is mainly distributed,have listed it as a rare and endangered plant.Therefore,it has became an urgent problem to systematically study the ecological adaptability of A.venetum and explore the causes of its endangerment.We selected wild A.venetum of four distributed regions(jinta county,minqin county,hangjinqi and baicheng)as the test materials in the study.Based on the study of community composition,population genetic diversity and soil environmental properties of wild A.venetum,physiological characteristics,transcriptomics and proteomics analysis of A.venetum under salt stress,and key regulatory proteins and genes of A.venetum salt tolerance were measured and identified to reveal the ecological adaptability of wild A.venetum and underlying mechanisms in response to salt stress.The study is beneficial to promote the protection and rational development and utilization of germplasm resources of wild A.venetum,and is of great significance to the development of national pharmacology and the construction of ecological civilization in China.The main results are as follows:1.There are differences in the biodiversity of the A.venetum plots in different regions.The species diversity of Zhaluteqi was the highest in five plots,followed by Minqin County,Baicheng City,Jinta County,and Hangjinqi had the lowest biodiversity.The species diversity of A.venetum community was closely related with precipitation,temperature and evaporation,repectively.The species diversity was positively and significantly correlated with the precipitation in the growing season,and the correlation of precipitation in May was higher than that in July,August and September.2.The genetic diversity of A.venetum was high at the species level and the population level,with a diversity index(He)of 0.3765 and 0.2616,respectively.The genetic differentiation coefficient among population groups was 0.3084 for Gst and1.1213 > 1 for gene flow(Nm),indicating a greater degree of differentiation among populations.Cluster analysis showed that the genetic distance among populations was not fully correlated with geographical distance,but different habitat conditions influenced the genetic differentiation of A.venetum populations.3.The soil of A.venetum plots was saline and alkali,and the soil fertility preservation is weak.There was closely related between leaf N and P content of A.venetum and soil salinity,and a negative correlation between N content and electrical conductivity(r =-0.436,P < 0.05).The leaf P content of A.venetum was significantly and positively correlated with soil conductivity(r = 0.442,P < 0.05).4.The adaptability to salt stress was enhanced by increasing the content of osmolytes and antioxidant enzyme activities in A.venetum.In comparison with the control treatment,salt stress treatment increased cell membrane permeability and decreased the soluble sugar content,but salt stress treatment did not substantially changed the soluble protein,indicating the ability of osmotic adjustment in A.venetum increased under salt stress.POD and SOD activities were also increased with the prolongation of salt stress and the maximum values of POD and SOD activities were 56.03 u/(g-min)and 214.08 U/g,respestively.5.Salt stress tolerance increased in A.venetum by increasing the expression of genes related to gluconeogenic processes,redox proteins and water channel protein activity.A comprehensive analysis of the transcriptome expression profile of A.venetum identified 11914 potential salt stress response genes in response to salt stress.Using the WGCNA method,the genes TRINITY＿DN102＿c0＿g1,TRINITY＿DN3073＿c0＿g1 and TRINITY＿DN6732＿c0＿g1,which are related to serine carboxypeptidase,SOS signalling pathway and heat-stimulated transcription factor,in the red module,were finally identified as the core genes of the module.6.Quantitative proteomics of A.venetum using TMT technology under salt stress,the proteins obtained from differential protein network interactions at different stress times were mainly ribosomal proteins,of which 60 S ribosomal protein L3-2(TRINITY＿DN13265＿c0＿g1＿i1＿9)was the core protein in the differential protein at both 12 h and 24 h of stress,indicating that the ribosomal proteins played an important role of A.venetum in response to salt stress.7.By transcriptome and proteome association analysis,a total of 428 genes and proteins with consistent expression patterns were obtained,among which 225 genes and proteins were up-regulated and 203 genes and proteins were down-regulated.Further GO enrichment analysis of the shared differential genes and proteins showed that the up-regulated genes and proteins were mainly involved in redox,sugar metabolism,photosynthesis,ion homeostasis and osmotic balance.The key enzymes and genes were important for enhancing salt stress tolerance in A.venetum.