Effects Of Physiological And Membrane Lipid Metabolism In Maize Seedlings Under NaCl Stress

Salt is one of the main environmental factors affecting crop growth and yield.Maize is the second largest food crop,and its salt-sensitive properties limit its growth on saline soil.The experimental material of this study was maize inbred line 344,and the two-leaf one-heart stage maize seedlings were treated with 150 m M Na Cl.The physiological response,regulation of lipid metabolism and gene expression of maize leaves under Na Cl stress were investigated and it is of great significance to to explore the regulation mode of salt response mechanism and to better understand the salt resistance of plants and develop new salt-resistant maize varieties.The main results are as follows:In this study,transcriptome sequencing of maize leaves under salt stress at 0,1,3 and 7 days was conducted on the bgiseq-500 sequencing platform.The sequencing results showed that the number of genes in the S7 d vs.C0 d control group was the largest,indicating that a large amount of salt responsive gene expression would be induced at 7 days of salt stress.Functional annotation of differentially expressed genes revealed that the S7 d Vs C0 d comparison group annotated a large number of differentially expressed genes,which were 10,366,of which the most differentially expressed genes were in the metabolic pathway.At the same time,some transcription factors might be involved in the regulation of salt-responsive genes such as MYB,WRKY,NAC and b HLH.There were also a large number of salt-responsive genes in hormone and osmotic regulation.Under salt stress,the activities of SOD,POD and MDA in the antioxidant system of maize seedlings increased with the increase of stress time,while the chlorophyll content also decreased under salt stress.At the same time,transcriptome data showed that SOD,POD-related genes and MDA-related LOX enzyme genes were up-regulated under salt stress,while chlorophyll synthesis and degradation genes were down-regulated.The consistency of physiological indexes of photosynthetic characteristics and gene expression laid a molecular foundation for further study on the changes of photosynthetic parameters under salt stress.ESI-MS/MS detection was performed on maize seedling leaves under salt stress at 0,1,3 and7 days.A total of 2 kinds of galactolipids,1 kind of thiolipids,6 kinds of phospholipids and 3kinds of lysophospholipids were detected.The most abundant lipids in maize leaves were galactolipids DGDG and MGDG.The percentage of DGDG increased under salt stress,the content of MGDG decreased,and the SQDG did not change significantly.The PG and PC in phospholipid decreased under salt stress,PE,PI,PS and PA increased under salt stress.The 36:6molecular species of DGDG and MGDG were the most abundant,indicating that the synthesis ofmaize galactolipid is completely dependent on the eukaryotic pathway and is a typical feature of18:3 plants.In the transcriptome data of S1 d Vs C0 d,S3d Vs C0 d and S7 d Vs C0 d,more than 460lipid-regulated genes were screened,and the number of genes with Log2FC?1.5 or ?-1.5 was the highest in the S7 d Vs C0 comparison group.The number of genes up and down was 122/30.The "phospholipid signal" and "eukaryotic phospholipid synthesis and editing" pathways were significantly differentially enriched in 15 lipid metabolic pathways,indicating that salt stress activates the phospholipid metabolic pathway.Based on the results of transcriptome and lipid group data,this paper describes the related pathways of membrane lipid metabolism and related genes,and initially established a gene-metabolite interaction network map of membrane lipid metabolism in maize leaves under salt stress.Salt stress activates the phospholipid synthesis pathway on ER and the de novo synthesis pathway of glycerolipids in chloroplasts,and most of the genes that catalyze these pathways are up-regulated.A significant up-regulation of PLD and NPC indicates that the PC-PA and PC-DAG pathways together provide precursors for chloroplast glycolipid synthesis.A total of 15 maize GPAT genes were obtained by whole genome isolation.Maize GPAT was divided into four clusters.The Zm GPAT gene family contains a phosphate acyltransferase(Pls C,smart00563)domain,and some genes also contain a ha Logenated dehydrohalase hydrolase(HAD-like,pfam12710)domain.Zm GPAT7 and Zm GPAT14 were expressed at high levels in almost all stages of vegetative and reproductive growth of maize.The Zm GPAT gene family was mostly upregulated under salt stress.