Study On Cold Stress To Metasequoia Glyptostroboides From Seed Germination To Early Seedling

The mechanism of low-temperature tolerance has always been one of the hotspots in the field of plant physiology research.Although much research has been done around the"ICE-CBF-COR"low-temperature tolerance regulation pathway,a considerable number of low-temperature response genes do not belong to this pathway,suggesting that there are other low-temperature tolerance regulation pathways in plants.Using special plants with strong low-temperature tolerance for low-temperature tolerance research,it is highly likely to find new regulatory mechanisms and related genes.Relict plants known as"living fossils"are precious plant resources that have survived through the Quaternary glaciation and are likely to have unique low-temperature tolerance mechanisms and related genes.However,there are few relevant studies so far.Given that germinating seed and early seedling is the most sensitive to the external environment during life history of plants,using the famous relict plant M.glyptostroboides as the research object,we would impose a continuous cold stress treatment during seed germination and early seedling establishment,and then explore the response mechanism to cold stress through a variety of research methods such as cell morphology,physiology and biochemistry,transcriptomics and metabolomics,bioinformatics and molecular biology,in order to make new development in plant low-temperature tolerance mechanism,further enrich and improve the regulation theory of plant low-temperature tolerance,and initially explore the survival mechanism of relict plants,and then promote agricultural and forestry resistance breeding and relict plant protection.Main results were as follows:1.M.glyptostroboides seeds have strong cold tolerance during the germination and seedling stage,among which the cold tolerance of seeds during imbibition,sprout and germination is stronger than that of seedlings.The minimum temperature that can be tolerated during the germination and seedling stage is 7°C.After comprehensively considering indicators such as germination rate,seedling rate and seedling vigor,9°C was determined as the cold stress temperature for this study.2.M.glyptostroboides seed germination and seedling stage will further induce osmotic stress and oxidative stress under cold stress,and compared with seed water absorption,sprout and germination stage,seedling stage is more sensitive to the two stresses,osmotic regulator substances and antioxidant defense systems Played a certain role in regulation and protection.In terms of osmotic regulation,its main role is proline,and soluble sugar and soluble Pro do not show significant effects;in terms of antioxidant defense,SOD,APX and CAT play a major role,in which SOD disproportionates superoxide anion on the one hand For hydrogen peroxide,on the other hand,excess ROS may also be scavenged through the water-water cycle;the large-scale scavenging of excess hydrogen peroxide is mainly dependent on the action of CAT;while APX seems to play a major role in cold stress signal transduction.3.The response of M.glyptostroboides seeds to cold stress during germination and seedling stage mainly involves energy metabolism,hormone signal transduction and antioxidant metabolism,and mainly involves the regulation of transcription factors such as LRR,AP2/ERF,b HLH,CBF and NAC.4.The energy metabolism involved in the response of M.glyptostroboides seeds to cold stress during germination and seedling stage mainly includes starch and sucrose metabolism,glycolysis/gluconeogenesis and citric acid cycle metabolic pathways,among which LST1,α-AMY,PYG,PK,pfk,MDH,SUC and NDUFS/V and other genes are likely to be key genes.The hormone signal transduction pathway mainly involves five hormones including ABA,GA,IAA,C₂H₄and SA,among which PYR/PYL,Sn RK2,PP2C,AUX,TIR,DELLA,PIF4,OPR and ACO1 are likely to be key genes.Antioxidative metabolic pathways mainly involve catalase and ascorbic acid-glutathione cycle,among which SOD1,CAT and GPX are likely key genes.5.The correlation coefficient between the q RT-PCR results of some differentially expressed genes and the transcriptomic analysis results is 0.9517,indicating that the transcriptomic data is reliable.6.Twenty-two hub genes were screened by WGCNA,mainly involved in citric acid cycle,hormone transport and metabolism,seed germination and seedling development,transmembrane transport and antioxidant defense.