Physiological Response And Metabolomics Of Hypnum Plumaeforme Under Drought Stress And Rehydration

Hypnum plumaeforme is a kind of moss with wide distribution and diverse habitats,which has strong drought tolerance.Water conditions limit the distribution of plants.Drought affects crop harvest and is an abiotic stress factor threatening global crop safety.Taking Hypnum plumaeforme as the research object,this study analyzed the morphological changes and physiological response of gametophytes of Hypnum plumaeforme under drought stress and rehydration by setting natural drought treatment with different duration(7 d,14 d and 21 d)and rehydration treatment with different duration(1d,3 d and 5 d);By means of metabolomics,the metabolic substances and their functions of Hypnum plumaeforme that play a major role in drought stress and rehydration conditions are excavated,in order to explain the molecular mechanism of Hypnum plumaeforme in response to drought and rehydration,in order to enrich the research data of plant drought resistance mechanism and provide a theoretical basis for vegetation restoration in arid areas such as desert and Gobi.The main results of this paper are as follows:1 Compared with the control group,the changes of chlorophyll of Hypnum plumaeforme under drought stress and rehydration were less,indicating that Hypnum plumaeforme has a strong protective ability of photosynthetic system under drought stress.The content of malondialdehyde and the activities of POD(peroxidase)and SOD(superoxide dismutase)increased under drought stress and decreased under rehydration conditions,indicating that drought stress increases the content of reactive oxygen species in Hypnum plumaeforme and damages the biofilm.Hypnum plumaeforme clears reactive oxygen species and protects the membrane system through the up regulation of antioxidant enzyme activity.Under the condition of rehydration,the soluble protein content of Hypnum plumaeforme increased,which may be that after rehydration,Hypnum plumaeforme quickly recovers its life activities and repaired the damage caused by drought.2 Through metabolomic analysis,Under drought stress,a total of 235 differential metabolites shared by each comparison group were annotated,which were divided into 43 subgroups including carboxylic acids and derivatives,fatty Acyls,flavonoids,organic oxygen compounds and an unknown classification.20 common metabolic pathways in three groups were screened under P<0.05 and VIP>1.The aflatoxin of Hypnum plumaeforme is up-regulated under drought stress,indicating that drought stress leads to the formation of toxic substances and damage to the body.Under drought stress,Hypnum plumaeforme mainly protects the body,and its amino acids such as L-serine,L-proline and L-isoleucine are significantly up-regulated.Amino acids,as the main osmotic regulators,improve the osmotic pressure of Hypnum plumaeforme,enhance the water absorption capacity and reduce water loss.At the same time,amino acids are used for signal transduction to respond quickly to the environment,eliminate ammonia toxicity,consume excess energy and protect the photorespiratory system.Under drought stress,the contents of citric acid,isocitric acid and succinic acid decreased,the content of Fructose 1,6-bisphosphate increased,accumulated sugars and increased osmotic pressure.At the same time,Hypnum plumaeforme reduce energy generation,and reduce the life activities of the body to reduce the damage caused by drought3 Under rehydration conditions,a total of 139 differential metabolites shared by each comparison group were annotated,which were divided into 37 subgroups including carboxylic acids and derivatives,fatty acyl,flavonoids,organic oxygen compounds and an unknown classification.28 common metabolic pathways in three groups were screened under P<0.05 and VIP>1.Under the condition of rehydration,Hypnum plumaeforme is mainly used to repair the damage caused by drought and quickly restore various life activities.The expression of amino acids and signal transduction related pathways was high,and amino acids continued to accumulate to enhance the water absorption capacity of Hypnum plumaeforme;The increase of unsaturated fatty acid content increases the fluidity and ductility of the membrane,which may be one of the main reasons why Hypnum plumaeforme can absorb water and saturate in a short time and respond quickly to the environment to restore life activities.Citric acid is up-regulated,1-Kestose is down regulated,a large amount of energy is generated,flavonoids and coumarin metabolites are synthesized to repair the damage of the body,at the same time,the mineral absorption pathway are expressed to restore life activities.4 Through the metabonomics comparison between drought stress and rehydration treatment,it is concluded that L-isoleucine and citrulline are up-regulated in drought stress and down regulated in rehydration treatment,which may be one of the main reasons for Hypnum plumaeforme to resist drought stress.Erythritol was down-regulated in drought stress and up-regulated in rehydration treatment,which may be one of the main reasons for the rapid water absorption and saturation of Hypnum plumaeforme.In addition,the flavonoid substances of Hypnum plumaeforme were also different in drought stress and rehydration treatment.The flavonoid content of luteolin was up-regulated in drought stress,and the contents of isorhamnetin and isoliquiritigenin were up-regulated in rehydration treatment.