| Drought is one of the most common environmental stresses affecting plant growth and development,and its impact is expected to increase with climate change and increasing water scarcity.Drought or soil water scarcity may be chronic or random and unpredictable in areas with water-scarce climates due to changes in weather conditions during plant growth.Given current and future population and social needs,water is an increasingly scarce resource,so emphasizing sustainable water use and understanding drought stress and water use related to plant growth is important for sustainable development.The negative effects of drought on plants are very harmful,including disruption of photosynthetic mechanisms,oxidation of cell membranes by reactive oxygen species(ROS),loss of cell turgor,and other effects resulting in growth and stunting.Plants respond to drought stress in the following ways,including accumulation of osmotic protectants to regulate osmotic pressure and antioxidant activity to remove reactive oxygen species,and changes in molecular level and metabolites to reduce the effects of drought stress.Xanthoceras sorbifolia Bunge is a kind of edible oil plant peculiar to China,mainly distributed in 14 provinces,autonomous regions and municipalities in northwest,North and east China,etc.The loess Plateau region with ravines and ravines is the most concentrated natural distribution area.At present,studies on drought resistance of X.sorb ifolium mainly focus on physiological indicators of yellow horn,but little is known about the relationship between drought tolerance and metabolome and transcrip tome.It is of great significance for researchers to understand the molecular response mechanism of yellow horn to drought stress and to develop new molecular methods to enhance its tolerance to drought.Therefore,in terms of physiological response,this study used the seedlings and mature plants of yellow horn as test materials to compare the physiological and biochemical differences in two different growth stages under drought stress and rehydration conditions.Through high-throughput sequencing and liquid chromatography-mass spectrometry(LC-MS)method,a comprehensive overview of the metabolome of yellow horn seedlings and transcrip tome,and concluded that the core control network in order to reveal the relationship between metabolites and transcription pathway,to excavate the drought critical genes and metabolites,and combined with fluorescence properties,physiological indicators,the structure of carbon change characteristics of water compounds,The molecular mechanism of its response to drought stress was described.The main contents and results are as follows:1.Response to drought stress in two different growth stages1 year seedlings and the mature plants as the test material,soil culture potted simulating natural drought,for two different drought stress treatment and water,so the two different growth stages in the process of drought stress and water fluorescence characteristics,antioxidant activity,the nonstructural carbohydrate response mechanism of drought resistance.Chlorophyll fluorescence and OJIP parameters indicated that the response and rehydration of the photosynthetic mechanism of yellow horn to drought stress was a very complex process,including heat dissipation at the organelle level to maintain the potential function of the photosynthetic apparatus under different drought intensity,resulting in the degree of recovery of photo synthetic performance after rehydration.With the increase of drought intensity,the malondialdehyde(MDA)content and ROS content increased synchronously with the increase of drought duration,indicating the accumulation of ROS and the increase of membrane lipid peroxidation under drought stress.At the same time,the accumulated ROS also stimulates the antioxidant enzyme protective system to continuously increase enzyme activity,thus maintaining the ROS balance.The membrane lipid peroxidation was reduced by catalase and glutathione reductase activities in seedlings,while the membrane damage was reduced by peroxidase and superoxide dismutase in mature plants.Drought stress caused different degrees of damage to the two different stages of yellow horn plants,and they were able to fully recover after rewatering during the study period,although it may take longer time to fully recover,indicating that yellow horn plants had strong drought resistance.Starch storage in leaves plays an important role in drought resistance and rehydration recovery of yellow horn for both seedlings and adult plants.During drought,starch content in the leaves of both adult plants and seedlings decreases to promote respiration and maintain osmotic regulation and water potential needs.During rewatering under moderate and severe drought treatments,adult plants did not deplete starch stores to promote hydraulic repair and regeneration due to "drought legacy effects".However,seedlings are more dependent on newly synthesized carbohydrates due to their small carbon stocks,and reduced carbohydrates after rehydration under drought stress are likely to be actively allocated to support growth.In conclusion,there were significant differences in drought response mechanism between seedlings and adult plants during drought stress and rehydration,and various physiological indicators showed that adult plants of yellow horn had stronger drought resistance.2、Transcriptome and metabolomics analysis of yellow horn seedlings under drought stressMetabolites and related genes of yellow horn seedlings in response to drought stress were analyzed using metabonomics and transcriptome methods.RNA-seq transcriptome data showed that a total of 3000 genes were down-regulated and 1762 genes were up-regulated when yellow horn seedlings were exposed to severe drought compared with the control.This may be due to the reduction of metabolic activity after stress,and is a protective mechanism by which plant hormones regulate the response of plants to drought stress by combining external stimuli with a complex regulatory network.In addition,according to the KEGG pathway analysis,the differentially expressed genes are mainly related to hormone signal transduction,MAPK signal transduction,photosynthesis,carbohydrate and amino acid metabolic pathways.Metabonomics analysis showed that under the condition of the water deficit,the metabolic balance of Yellow horn leaf has been readjusted,accumulation of metabolites including sucrose,stachyose,proline and phosphoric acid,choline,showed that metabolites involved in plant stress reaction of sugar and proline accumulation under drought stress ACTS as a protectant,related gene expression also raised.In addition,transcriptome and metabolomics analysis revealed that differentially expressed genes and metabolites closely related to starch and sucrose metabolism play important roles in leaf drought stress response.3、AP2/ERF gene family analysis of Yellow horn under drought stressAP2/ERF transcription factors play an important role in plant growth,development,metabolism and response to biological and abiotic stresses.In this study,145 AP2/ERF members were identified and their genetic structure,evolutionary characteristics and expression pattern were studied and analyzed.Phylogenetic analysis showed that these genes were divided into four groups,including 21 AP2 genes.,119 ERF and DREB genes,4 RAV genes and 1 Soloist gene,which were unevenly distributed on 15 chromosomes.Structural analysis of XsAP2/ERF genes showed that 87 XsAP2/ERF genes lacked introns.There were 75 XsAP2/ERF genes and AP2/ERF collinear relationship between XsAP2 and A.thaliana reflecting their similarity.The presence of multiple CRE in XsAP2/ERF promoter is associated with abiotic stress,suggesting that XsAP2/ERF activity may contribute to the adaptation of yellow horn to environmental changes.Tissue specific analysis showed that XsAP2/ERF was expressed in roots and leaves of yellow horn seedlings,39 XsAP2/ERF were not expressed,but 58 XsAP21ERF were expressed in all samples.The analysis of AP2/ERF gene expression patterns under different drought stress showed that XsAP2/ERF gene played an important role in drought response.The results of this study set the stage for future analyses to elucidate the importance of AP2/ERF transcription factors in the function of yellow horn and drought stress response.These results provide valuable resources for better understanding the biological role of AP2/ERF gene in yellow horn.This paper is based on the physiological characteristics,DEGs and metabolites detection,and abundant biological processes and metabolic pathways analysis of yellow horn under drought stress.Our results provide a possible insight into the molecular mechanism of yellow horn response to drought stress. |
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