Resistance And Adaptation Of Tibet Wild Elymus Nutans To Low Temperature Stress

Low temperature is one of the main environmental factors restricting plant growth in high altitude areas in Tibet.Elymus nutans as a common gramineous forage grass in the Tibet Plateau,has the characteristics of strong stress resistance and high grass yield.Therefore,it is very important to explore the cold response characteristics of Tibet wild Elymus nutans.In this study,wild Elymus nutans in Baqing,wild Elymus nutans in Anduo,Wild Elymus nutans in Luoma and wild Elymus nutans in Dangxiong.By studying the effects of low temperature stress on its seed germination,phenotypic characteristics,physiological and biochemical indicators,transcription and metabolism,comprehensively explored the cold response characteristics of Tibetan wild Elymus nutans from various aspects and perspectives.The evaluation of germplasm resources of Elymus nutans and the research and utilization of its cold resistance mechanism provide reference basis.The main results are as follows:(1)Low temperature stress has a certain inhibitory effect on the seed germination and seedling growth of Elymus nutans in Tibet,and it will intensify with the extension of the stress time.The fuzzy membership function method was used to comprehensively analyze the membership functions of 6 indexes of each material,including germination rate,germination potential,germination index,vigor index,root length,and seedling length.It was found that during the seed germination period,the wild Elymus chinensis D The value is 0.59,which has the strongest cold resistance;the D values of Roman wild Elymus nutans and Elymus nutans are 0.47 and 0.43 respectively,followed by cold resistance,and the D value of Amdo wild Elymus nutans It is 0.38,the cold resistance is the weakest.(2)At 5°C,the growth of each material was significantly inhibited.After 28 days of growth at 5°C,each material was still alive,but the plants were short and thin,the leaves were yellow,and local necrosis was obvious,and it was obvious that they suffered from cold damage.Signs.The content of malondialdehyde,free proline activity,peroxidase activity,catalase activity,and the leaf water content decreased significantly.Using the membership function weighting method,the 4 test materials are malondialdehyde,soluble sugar,proline,catalase,peroxidase activity,superoxide dismutase(SOD),plant height and leaf water content,etc.A comprehensive analysis of the membership functions of 7 indicators found that Elymus nutans in Baqing had the strongest cold resistance,followed by Elymus nutans in Luoma and Elymus nutans in Dangxiong,and Elymus edulis Anduo was the weakest.(3)Through RNA-sep high-throughput sequencing,it was found that under 5℃ low temperature stress,there are 3673 differentially expressed genes in the leaves of Elymus nutans in Baqing |log2Fold Change|>1,of which 1720 genes are up-regulated,1953 Genes are down-regulated.There are 834 differential genes in |log2Fold Change|>6,of which 132 are up-regulated and 711 are down-regulated.Through GO annotation and KEGG analysis of 834 differential genes of |log2Fold Change|>6,it is found that the functions of differentially expressed genes are mainly organic nitrogen compound metabolism,lipid transport,peptide metabolism,ribosomal biosynthesis,ribosomal components,Cytoplasmic components,membraneless organelle components,chitin binding,hydrogen ion transport across membranes,etc.The KEGG pathways enriched by differential genes mainly include starch and sucrose metabolism,photosynthesis,α-linolenic acid metabolism,phenylpropanoid biosynthesis,galactose metabolism,flavonoid biosynthesis,alanine,aspartic acid and glutamine Acid metabolism,phenylalanine,tyrosine and tryptophan biosynthesis,linoleic acid metabolism,and plant hormone signal transduction,etc.(4)Metabolomics analysis was carried out using targeted metabolome technology,and it was found that under 5℃ low temperature stress,a total of 947 metabolites were detected in the leaf tissue of Elymus nutans and 249 different metabolites were screened.Among them,198 are up-regulated and 51 are down-regulated.These differential metabolites mainly involve sugars and their derivatives,amino acids and their derivatives,alkaloids and their derivatives,indole and their derivatives,amines,fatty acyls,Flavonoids,etc.The above differential metabolites were analyzed by the KEGG pathway,and it was found that the main enrichment pathways were arginine biosynthesis,ABC transporter,2-oxocarboxylic acid metabolism,citrate cycle(TCA cycle),and alanine,Aspartic acid and glutamate metabolism,arginine and proline metabolism,butyrate metabolism,amino acid biosynthesis,glutathione metabolism and propionate metabolism,etc.Correlation analysis of the differential metabolites of Top20 showed that the differential metabolites such as D-proline and cycloleucine were completely positively correlated.The change trend is consistent,indicating that the cold resistance of Elymus chinensis is controlled by the metabolism of multiple secondary metabolites.(5)The cold resistance of Elymus nutans is regulated by multiple metabolic pathways,which are closely related to photosynthesis,carbohydrate metabolism,polyamine metabolic pathways,α-linolenic acid metabolic pathways,etc.