Transcriptome-based Response Of Populus Euphratica Seed Germination To Salt Stress And Exogenous Hormones And Analysis Of AP2/ERF Gene Family

Salt stress seriously affects the growth,development and reproduction of plants.To study how Populus euphratica responds to salt stress to improve the salt tolerance of P.euphratica is of great significance to the evolutionary analysis of the adaptability of P.euphratica to extreme desert environments.In this study,the RNA of P.euphratica seeds treated with different concentrations of salt stress was analyzed by transcriptome sequencing to study the mechanism of response to salt stress.Based on the whole genome of P.euphratica,the AP2/ERF（APETALA2/ethylene-responsive element binding proteins）transcription factor was analyzed.Identification and expression analysis of salt stress.The main findings are as follows:（1）Under suitable temperature and light conditions,when the salt concentration is higher than0.20mol/L,the germination of P.euphratica seeds will be significantly inhibited;the exogenous hormone-gibberellins（Gibberellins,GA₃）can promote the growth and germination of P.euphratica seeds,The exogenous hormone Abscisic acid（ABA）can inhibit the growth and germination of P.euphratica seeds.（2）By comparing the differences in gene expression in the NaCl vs.NaCl＿CK,ABA vs.ABA＿CK,GA₃ vs.GA₃＿CK,and ABA vs.GA₃ treatment groups,there were 9005（3796 up-regulated and 5209down-regulated）and 7661（2858 up-regulated）groups in the 4 groups,respectively And 4803down-regulated),7509（4319 up-regulated and 3183 down-regulated）,2316（1040 up-regulated and 1276down-regulated）candidate differentially expressed genes were identified as salt stress genes;enriched by GO function of differentially expressed genes The analysis found that the pathways such as transcriptional regulation,ethylene-activated signaling pathway,abscisic acid-activated signaling pathway,auxin-activated signaling pathway,and response to cold and water shortage are more enriched.Therefore,we speculate that ABA and ETH may play a key role in adaptation to salt stress and hormone regulation during the germination of P.euphratica seeds.740,698,214,and 665 differentially expressed transcription factors were identified in 4 different comparison groups,which were distributed in 59,56,43,and 57 transcription factor families,including AP2/ERF-ERF,NAC,MYB,WRKY,b HLH,b ZIP family,etc.,AP2/ERF-ERF family genes have a large number of differentially expressed genes,indicating that AP2/ERF family genes play an important role in response to salt stress in P.euphratica.（3）Under salt stress and exogenous hormone treatment,there were 11,239 variable splicing events in4893 genes in P.euphratica seed germination,of which intron retention events（RI）occurred the most.GO function annotations show that the main functions of genes that undergo variable splicing are metabolism,cell structure,and substance binding.NaCl vs.NaCl＿CK,ABA vs.ABA＿CK,GA₃ vs.GA₃＿CK,ABA vs.GA₃ 4 common genes accounted for only 1.7%,1.0%,0.8%,1.2%of the total genes of differentially expressed genes and variable splicing genes,respectively.It showed that salt stress,ABA and GA₃ induced P.euphratica gene expression level and variable shear level have a low degree of coincidence.（4）The 197 P.euphratica AP2/ERF family members identified in this paper were analyzed by relevant bioinformatics.Based on transcriptome data,the differential expression patterns of AP2/ERF genes in four different comparison groups in salt stress,foreign hormone ABA and GA₃ were analyzed,and three genes that might affect seed germination under salt stress were found.Through transcriptome analysis and AP2/ERF gene family analysis,it is helpful for us to discover possible salt-tolerant genes during the germination of P.euphratica seeds and lay the foundation for the subsequent cloning of salt-tolerant genes.