The Response Of Suaeda Corniculata Under Salt And Alkali Stress And The Functional Characterization Of ScHSFA1d

Suaeda corniculata is a euhalophyte native to the saline-alkali soil of Northeast China which shows a higher alkali tolerance than other Suaeda plants.However,the molecular basis of the S.corniculata adaptation to salt and alkali stress is still not very clear.Transcription factors play an important role in plant stress resistance,through activating or inhibiting the expression of multiple target genes.Heat shock transcription factor(HSF)is widely involved in plant growth and development and stress response.At present,the function of HSF genes needs to be further studied such as regulating plant salt stress.And the function of HSF in halophytes has not been reported,especially in Suaeda.In this study,S.corniculata was used as the research material,and the metabolic molecular basis of S,corniculata in response to salt and alkali stress was systematically analyzed by using physiological and omics analysis.We screened a gene schsfald that may regulate the salt tolerance of S.corniculata.Through gene function verification,we preliminarily understand the function of ScHSFA1d in positively regulating plant salt tolerance.These studies laid a theoretical foundation for further exploring the mechanism of action of ScHSFA1d.The main results are as follows:(1)Physiological analysis of saline-alkali stress of S.corniculata showed that the effect of alkaline salt stress on plant growth was more serious than neutral salt stress.Affected by salt and alkali stress,the fresh weight and relative water content in roots were decreased significantly.The level of intracellular ROS increased under NaHCO3 and NaCl stress.Antioxidant enzyme activities and non-enzymatic antioxidant contents of ROS were changed to varying degrees.The membrane system of root cells was damaged to a certain extent.Osmoregulatory substances(proline and betaine)were accumulated in cells to cope with salt and alkali stress.(2)The results of 1H NMR metabolome analysis showed that the contents of leucine,isoleucine,valine,glutamine,malicacid and 2-oxoglutarate were significantly increased in the roots under NaCl stress.The metabolic characteristics after NaHCO3 treatment are not exactly the same.The contents of malonate,choline and betaine were increased under NaHCO3 stress,while the contents of malicacid,succinic acid and sucrose were decreased.In the metabolome results,we found that the content of betaine after two treatments was much higher than that of other metabolites.In addition,the contents of choline phosphate and choline,metabolites related to betaine anabolic pathway,were also significantly increased under NaHCO3 treatment.The accumulation of glycine betaine mainly contributes to the reconstruction of osmotic homeostasis during stress.(3)Proteomic studies showed that 65 and 32 proteins were differentially expressed under salt and alkali stress,respectively.Many biological functional pathways showed different responses under salt and alkali stress,such as carbohydrate metabolism,fatty acid metabolism,antioxidant system and hormone signal pathway,such as jasmonic acid signal pathway.In addition,the accumulation of germinating proteins actively participates in the process of fatty acid metabolism and antioxidation,and the changes of protein folding,processing and transport pathways are complex,which plays an important role in the response of S.corniculata to saline-alkali stress.At the same time,ASA-GSH cycle and PRX/TRX pathway may play an important role in maintaining redox homeostasis,removing excess ROS and reducing oxidative damage,to help plants tolerate salt and alkali stress.(4)Transcriptome analysis showed that 997 and 890 genes were involved in the response NaHCO3 and NaCl stress.The genes involved in the biological metabolic processes such as stimulation response,cell growth,immune process and antioxidant activity play an important role in the salt-alkali response.A large number of differentially expressed genes are enriched in endocytosis,plant hormone signal transduction,endoplasmic reticulum protein processing,carbon sequestration of photosynthetic organisms,tyrosine metabolism,vitamin E and methionine metabolism,arginine and proline metabolism,phenylpropane compounds ?linolenic acid metabolism,starch and sucrose metabolism,amino acid biodegradation and carbon metabolism.By analyzing the transcription factors in the transcriptome data,it was found that 48 transcription factors were differentially expressed under NaHCO3 and NaCl stress.HSFs were the most differentially expressed transcription factor in this study,and half of HSFs were significantly induced under NaHCO3 and NaCl stress.(5)A HSF transcription factor closely related to saline-alkali response was screened from the transcriptome data of S.corniculata.It was finally named schsfald after phylogenetic and protein structure analysis.Through qRT-PCR,it was found that schsfald was up-regulated in roots and leaves under NaHCO3 and NaCl stress.The results of subcellular localization showed that ScHSFA1d was located in the nucleus.The results of the transcriptional self-activation experiment showed that the transcriptional activation region of ScHSFA1d contained an AHA activation region from 411aa to 461aa on the amino acid sequence.(6)Overexpression of ScHSFA1d enhanced the tolerance of transgenic yeast and Arabidopsis to salt and alkali stress.The degree of stress damage of overexpressing ScHSFA1d Arabidopsis is lower than that of wild-type Arabidopsis.ScHSFA1d can improve the salinealkali tolerance of Arabidopsis.HSFA1d function deletion caused by Arabidopsis hsfa1d mutant,there is no significant difference in growth phenotype and ROS accumulation between hsfa1d mutant and wild-type Arabidopsis after stress,and the plant does not show salt-sensitive phenotype.These results show that endogenous HSFA1d gene in Arabidopsis does not play an important role in regulating salt and alkali resistance of Arabidopsis,The results show that there are functional differences between the two heat shock transcription factor HSFA1d homologous genes of sweet soil plant Arabidopsis and halophyte S.corniculata,which reflects the ScHSFA1d of S.corniculata.This genotype plays an important regulatory role in salt and alkali resistance.