| Halophytes are an important guarantee for the safety and health of desert ecosystem.Borszczowia aralospica is a salt accumulating plant of Borszczowia in Chenopodiaceae.It has strong salt alkali tolerance and barren tolerance.It is the main constructive species in Gurbantunggut Desert.Previous studies confirmed that the diversity of endophytic bacteria increased with the increase of salt stress gradient,which showed that it was more dependent on the symbiosis of endophytic bacteria under salt stress.In order to understand the metabolic response of Borszczowia aralocaspica under different salt gradient stress,this study took wild Salicornia heterophylla and cultivated Borszczowia aralocaspica in a series of salt gradient soil with 0%,20%,50% and 70%in situ desalination as materials,and detected the evolution of metabolite composition in root and leaf tissues at three development stages by GC-MS technology,so as to reveal the metabolic mechanism of Borszczowia aralocaspica adapting to salt stress,coupled with the evolution of endophytic bacterial composition under different salt gradients in the early stage,in order to understand the relationship be tween metabolites and endophytic flora,so as to provide a scientific basis for revealing the mechanism of isozipeng adapting to high salt environment.The metabolites of roots and leaves in young seedling stage,growth stage and flowering stage were detected,and 180 identifiable components were obtained.The analysis of the molecular weight composition of metabolites showed that they were mainly composed of components with molecular weight less than 300,of which the components with molecular weight of 100-200 accounted for more than 58%.The analysis of the category composition of metabolites showed that organic acids,sugars and derivatives,amino acids and derivatives,alcohols and amines were the main components.The analysis of the relative proportion of metabolites showed that there was no significant difference between different growth stages.The analysis of differential metabolites in roots and leaves at different development stages showed that only 65 and 31 metabolite components were related to the development stage respectively.These components were mainly composed of organic acids,sugars and amino acids,and most of them had molecular weight less than 200,which changed significantly from seedling stage to growth stage.The results showed tha t different developmental stages and different tissues of Borszczowia aralocaspica had different responses to the environment,and more complex responses occurred in the roots,which helped the plants adapt to the environment.Four prepared salt gradients,cultivated and wild,were analyzed as five salt gradients.The molecular weight analysis of metabolites showed that the substances with molecular weight of 100-200 were mainly in response to salt gradient stress.The analysis of the category composition of metabolites showed that organic acids,sugars,amino acids and other substances responded to salt gradient stress,and the responses in roots and leaves were different.With the increase of salt gradient stress,the components of citric acid,fumaric acid,ethanol galactose,trehalose,mannitol and proline in root and leaf tissues changed.The results showed that the strategy of dealing with salt stress was to increase proline and glycolic acid in root and reduce malic acid and mannitol in leaves;In the seedling stage,the content of proline,n-leucine,galactose and threonic acid increased,succinic acid and eicosapentaenoic acid increased in the growth stage,and citric acid and galactitol increased in the flowering stage in response to the threat of high salt gradient.The results showed that the response components to salt stress were different in different growth stages.Combined analysis of metabolite composition and microbial diversity of different salt gradients showed that there was a very significant correlation between metabolites and endophytic flora(P < 0.01).OTU level coupling analysis of endophytic diversity showed that metabolites were mainly related to microbial groups such as OTU1138(Rolstonia),OTU508(Marinobacter),OTU2615(Pseudomonas),OTU838(Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium).The evolution of metabolite components in different salt gradients was significantly related to the diversity of endophytic bacteria.The metabolites in 0% salt gradients were mainly relat ed to Ralstonia,Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium and so on.The salt gradient of 20% is mainly related to Pseudomonas and Devosia.The 50% salt gradient was mainly related to Ralstonia and Allorhizobium-Neorhizobium-PararhizobiumRhizobium.70% of the salt gradient is mainly related to Devosia and Klebsiella.Wild samples are mainly related to Marinobacter and Methylophaga.Small molecular substances closely related to salt tolerance in different tissues are related to endophytic flora.Among them,root metabolites are highly related to endophytic flora,mainly including Marinobacter,Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium,Devosia and kushneria;The correlation between metabolites in leaves and endophytes is low,indicating that most microbial groups in leaves may come from air.The results showed that the regulation of metabolism by endophytic bacteria in roots played a more important role in its environmental adaptability under salt gradient stress.The results showed that salt gradient stress changed the metabolites of Borszczowia aralocaspica,which was related to the development cycle and endophytic diversi ty.This study lays a foundation for revealing the environmental adaptability of halophytes from the level of metabolite response.The coupling analysis of the evolution of metabolites and the structure of endophytic bacteria under different salt gradient stress has important scientific significance for revealing the symbiotic stress resistance mechanism,has significant innovation,and has positive guiding value for using microorganisms to promote plant salt resistance. |
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