Study On Apple Sugar Transporter MdSTP1 In Mediating Plant Growth And Abiotic Stress Response

Whether in animals or plants,sugar plays an important role in the growth and development of organisms and plays a role in the whole course of life.Sugar not only has the function of basic skeleton substance and nutrient substance,but also participates in the whole life process of plants and animals as energy and signal substance.In most plants,the sugars produced by photosynthesis are transported mainly in the form of sucrose,and a few in the form of sorbitol.In Arabidopsis thaliana,sugar can induce the transcription of thousands of genes and participate in metabolic pathways such as sugars and lipids.In addition,sugar also forms a regulatory network with various plant hormones(such as ABA and ethylene),participating in the regulation of physiological processes at different stages of plants.Studies have shown that sugar is also involved in nitrogen use and biological and abiotic stress in response to a variety of environmental factors.Plants assimilate the carbon dioxide in the environment into monosaccharides through green tissues,but monosaccharides such as glucose and fructose are unstable and easy to affect the osmotic potential of cells,which are hydrolyzed by enzymes.Therefore,plant bodies are mostly transported in stable forms such as polysaccharides and sugar alcohols.In plants,the transformation and transportation of different sugars are particularly important.In the long course of evolution,plants and animals have formed a variety of efficient mechanisms to sense changes in sugar content and produce a variety of physiological changes to respond to environmental factors and regulate the growth and development of individuals.Sugar transporters,including monosaccharides and polysaccharide transporters,mediate the transport,absorption and utilization of sugars in plants.In addition,some sugar transporters are involved in plant stress defense.For many years,apple tree has been an important economic tree species in China and has an important position in the international fruit market.Sugar is crucial to the growth of fruit trees,the quality of apple fruit and the formation of economic value.At present,studies on sugar transporters are mainly focused on model plants such as Arabidopsis thaliana,while the regulation of sugar accumulation in apples remains to be further studied.Therefore,revealing the physiological functions of sugar transporters in apples is of practical significance to the breeding and production of apples.In this study,35 main cultivars of apple commonly grown in China were selected to analyze the components of flavor substances such as soluble sugar and organic acid,and the correlation between soluble sugar and other substances.A gene MdSTP1 encoding a monosaccharide transporter in apple was cloned from royal Gala.Expression analysis showed that MdSTP1 was mainly expressed in fruits,and the expression level increased gradually with the development of fruits.Salt,ABA and sugar treatment could induce the expression of MdSTP1.MdSTP1 heterotopia and overexpression of Apple callus were used to further elucidate the regulatory function of MdSTP1 in sugar accumulation and abiotic stress resistance.The specific research results are as follows:1.Analysis of sugar content of main cultivars of different applesThe main soluble sugars in apple fruits are fructose and glucose,which are related to some organic acids.2.Analysis of dynamic changes of sugar during fruit developmentIn the later stage of fruit development,fructose and glucose accumulated rapidly and the content was stable.3.Spatiotemporal expression analysis of MdSTP1Quantitative and chemical staining techniques were used to analyze the expression characteristics of MdSTP1 in time and space.The results showed that MdSTP1 was expressed in various tissues,and the expression level varied greatly with the development of fruit.4.MdSTP1 gene regulates sugar accumulationWe analyzed the response of MdSTP1 to different sugars,and it was found that the expression of MdSTP1 increased significantly in a short time after treatment with glucose,fructose and sucrose.In both Arabidopsis and apple callus,the soluble sugar content was significantly increased and the growth potential was better than that of the control group.5.MdSTP1 regulates plant growth and developmentIt was found that after the treatment of glucose and sucrose,the length of the primary root and the number of the lateral roots decreased significantlyv in Arabidopsis.The above results indicated that MdSTP1 enhanced the sensitivity of plants to glucose and sucrose.In addition,the growth experiment also found that the flowering time of MdSTP1 transgenic Arabidopsis changed earlier than that of the wild type,and combined with the increased soluble sugar content of Arabidopsis thalli transformed plants,it was speculated that MdSTP1 may participate in the regulation of flowering through sugar accumulation level.6.Study on resistance of MdSTP1 to abiotic stressqRT-PCR analysis showed that MdSTP1 could respond to ABA and salt treatment.When MdSTP1 Arabidopsis strains and wild-type arabidopsis strains were treated with ABA and high concentration of salt,it was found that the growth of MdSTP1 Arabidopsis strains was significantly worse than that of wild-type Arabidopsis strains.MdSTP1 reduced the tolerance of Arabidopsis to ABA and salt.