| Growth and development of plants are affected by salt stress,which hinders agricultural production and development.How to enhance salt tolerance of plants is a major issue that agricultural scientists and botanists have to face today.In this study,the coastal brush Atalantia buxifolia was used as the experimental material,and its seeds and seedlings were treated with salt stress.Its growth,the morphology,physiology,and biochemistry were analyzed.At the same time,transcriptome analysis and Ab NHX1 gene cloning were carried out in order to explore how the plant responses to salt stress and functions of related salt-tolerant genes,providing relevant basis for genetic improvement of horticultural plants.The results were as follows:（1）Salt stress had an inhibitory effect on the seed germination of A.buxifolia.The increase in Na Cl concentrations resulted in the decrease in germination rates,germination potential,germination index,and vigor index of A.buxifolia seeds,and as well growth of epicotyl and radicle,biomass and relative water concentrations of A.buxifolia seedlings.But the relative salt damage rates of A.buxifolia seeds showed an upward trend.However,the seeds of A.buxifolia can adapt to the growth of 100 m M Na Cl concentration to a certain extent.The germination rates,germination potentials,relative salt injury rates,biomass and relative water concentrations did not change significantly,compared with the control treatment.And the seed germination rates of A.buxifolia still had 38.67%under the high concentration of 300 m M salt stress.（2）With the increase in Na Cl concentrations,the leaves gradually became yellow,and leaves of seedlings under high Na Cl concentration（300 m M）appeared withering.At the same time,plant height,root length,and root tips decreased.The base diameters,fresh weight,dry weight,related water concentrations,and root surface areas showed an increasing trend when Na Cl concentrations were between 0 and 100 m M,while these indexes showed a decreasing trend when Na Cl concentrations were more than 100 m M.But the root diameters increased as Na Cl concentrations increased.The decrease in chlorophyll concentrations led to the decrease in gas exchange in the leaves of A.buxifolia seedlings under salt stress.With increase in Na Cl concentrations,the activities of superoxide dismutase（SOD）,catalase（CAT）,peroxidase（POD）,ascorbate peroxidase（APX）,and glutathione reductase（GR）generally showed an increasing trend,while CAT and SOD had the lowest activity at 100 m M Na Cl concentration,resulting in the lowest concentrations of hydrogen peroxide（H2O2）under this treatment.In addition,APX reached the highest at 200 m M Na Cl concentration;when the Na Cl concentrations increased from 0 m M to 200 m M,the concentrations of ascorbic acid（As A）and glutathione（GSH）increased,and then the concentrations of these two indexes decreased when Na Cl concentrations were more than 200 m M.The concentrations of soluble proteins and proline increased with the increase in Na Cl concentrations,while the concentrations of soluble sugars（SS）decreased as increase in Na Cl concentrations from 0 m M to 100 m M,and the concentrations of SS increased when Na Cl concentrations were more than 100 m M.The concentrations of malondialdehyde（MDA）and relative electrolyte leakage increased with the increase in Na Cl concentrations.However,when the Na Cl concentration was 100 m M,the plant height,base diameters,dry weight,root related indexes,relative water concentrations,POD,CAT,APX,GSH,As A,H2O2,MDA and relative electrolyte leakage of A.buxifolia seedlings did not show significant changes,compared with the control treatment.（3）Analysis of transcriptome analysis showed that a total of 59.3 Gb of clean bases were obtained.The alignment rate of the reference genome was between 92.83%and94.87%,and a total of 29,959 Unigenes were annotated.GO enrichment showed that a total of 12,081 Unigenes and 787 GO detailed annotation information were annotated.GO enrichment showed that the three major sub-nodes were enriched in various metabolic process,biosynthetic process,membrane,and binding.The KEGG pathway annotation shows that differential genes were mainly enriched in some pathways,such as photosynthesis antenna proteins,plant hormone signal transduction,glutathione metabolism,and starch and sucrose metabolism,etc.In addition,differentially expressed genes had been annotated into 45 transcription factor families,including the largest number of b HLH family,NAC family,WRKY family,MYB-related family,b ZIP family,etc.（4）The Ab NHX1 gene of A.buxifolia was successfully cloned and the plant expression vector p BI121-Ab NHX1 was successfully constructed,which provided a basis for the subsequent functional verification of the gene.In summary,this study concluded that with the increase in Na Cl concentrations,germination rates of A.buxifolia seeds and the growth of its seedlings were inhibited.However,when the salt concentration was 300 m M,the seeds and seedlings of A.buxifolia still had certain vitality,and could induce the expression of related genes to resist the harm of salt stress,which indicated that A.buxifolia had certain salt tolerance. |
