Preliminary Analysis Of Physiological And Molecular Mechanisms Of Wheat (Triticum Aestivum L.) Response To Major Climate Change Factors

In the future,climate change is accompanied by elevated CO₂ concentrations,temperature and increased drought in some regions.Wheat（Triticum aestivum L.）is an important food crop in China.It is of great significance to study the response mechanism of wheat to major climate change factors.In this study,winter wheat varieties Hanxuan 3 and Yannong 19 were used as test materials.The open-top chamber（OTC）was used to simulate the water and drought environment with elevated CO₂ concentration and temperature in the future and the water and drought environment under the current climatic environment conditions.Four environmental treatments were set: normal temperature + normal CO₂ concentration + water（NT + NC +WW）,normal temperature + normal CO₂ concentration + drought（NT + NC + DS）,high temperature + high CO₂ concentration + water（HT + HC + WW）,high temperature + high CO₂ concentration + drought（HT + HC + DS）.Four sowing dates were set for each environmental condition.Through the analysis and comparison of flag leaf photosynthetic related traits and agronomic and yield-related traits in different environments,the optimal sowing dates were determined under the current and future climatic environment conditions.Four environments were set up in OTC room: high temperature + high CO₂ concentration +water（HT + HC + WW）,high temperature + high CO₂ concentration + drought（HT + HC +DS）,high temperature + normal CO₂ concentration + water（HT + NC + WW）,high temperature + normal CO₂ concentration + drought（HT + NC + DS）.At the best sowing date,the photosynthetic related traits,agronomic and yield related traits of flag leaves during filling date after post-anthesis were analyzed and compared.To explore the physiological mechanism of CO₂ concentration,water and interaction affecting wheat growth and development.Transcriptome sequencing was performed on flag leaves of Yannong 19 at heading stage and23 d after anthesis in different environments,to screen differentially expressed genes under different CO₂ concentrations and water conditions,and preliminarily analyze the molecular mechanism of wheat response to major climate change factors.The main research results were as follows :1.Through the comprehensive analysis of agronomic and yield-related traits,SPAD,photosynthetic parameters and chlorophyll fluorescence parameters under different environments,it was found that the optimal sowing date of wheat was the middle ten days of October（before and after October 11）under current climatic conditions regardless of water conditions.In the future climate environment,the best sowing date of wheat is late October（October 24 to October 29）.2.Comprehensively analyzing the effects of CO₂ concentration,water content and interaction on agronomic and yield-related traits of the two varieties,showed that CO₂ concentration had significant effects on panicle length,spikelet number,effective tiller number and economic yield,and water content had significant effects on plant height,thousand grain weight,effective tiller number,biological yield and economic yield.The interaction between CO₂ concentration and water had a significant effect on economic yield.3.Under the high temperature environment in OTC,high CO₂ concentration affected the various stages growth and development on wheat.The growth and development of wheat were advanced,fertility period was shortened,the maturity period had been advanced 1 to 11 days,and had been advanced 3 to 13 days in drought.Under the interaction of high CO₂ concentration and drought,compared with normal CO₂ concentration and irrigation,the maturity of the two varieties was 10 to 14 days earlier from returning green to mature each stage.4.Under the high temperature environment in OTC,under irrigation conditions,the WUE of high CO₂ concentration treatment was significantly higher than that of normal CO₂ concentration treatment under high temperature climate environment in the future.Under drought condition,Ci and WUE of high CO₂ concentration treatment were significantly higher than those of normal CO₂ concentration treatment.Regardless of water conditions,the Gs of high CO₂ concentration treatment was significantly smaller than that of normal CO₂ concentration treatment.Under the same CO₂ concentration,SPAD,Pn,Tr,Gs and Ci of drought treatment were significantly lower than those of irrigation treatment.The interaction between CO₂ concentration and water was not significant.5.Under the high temperature environment in OTC,under irrigation conditions,qp and Fv’/Fm’ of high CO₂ concentration treatment were significantly higher than those of normal CO₂ concentration treatment under high temperature climate environment in the future.Under drought condition,Fv/Fm and ETR of high CO₂ concentration treatment were significantly higher than those of normal CO₂ concentration treatment.Regardless of water conditions,NPQ of high CO₂ concentration treatment was significantly lower than that of normal CO₂ concentration treatment.Under the same CO₂ concentration,qp of drought treatment was significantly lower than that of irrigation treatment.The interaction between CO₂ concentration and water was not significant.6.The DEGs of high CO₂ concentration compared with those normal CO₂ concentration were analyzed under irrigation conditions at heading stage.It was found that the gene encodingβ-fructosidase（INV）was up-regulated.The gene encoding 1,5-diphosphate ribulose carboxylase（Rubisco）was down-regulated.It indicated that high CO₂ could reduce carbon fixation and photosynthetic capacity in the process of turning vegetative growth to reproductive growth at heading stage,but decompose more monosaccharides and release energy to maintain this process under irrigation conditions.7.The DEGs at high CO₂ concentration were compared with those at normal CO₂ concentration under irrigation at 23 d after anthesis,and it was found that the genes encoding1,4-α-glucan branching enzyme（GBE）,light system I subunit,light system II protein,cytochrome c6,ferrite reducing protein（Fd）,plastocyanin（PC）,light-harvesting chlorophyll a / b binding protein complex（LHCB）,dihydrothionamide dehydrogenase（DLD）,superoxide dismutase（SOD）,and heat shock proteins（HSPs）were up-regulated.Genes encoding INV,trehalose 6-phosphate synthase（TPS）and phosphoenolpyruvate carboxykinase（PEPCK）were down-regulated.It indicated that under irrigation conditions,high CO₂ could enhance the photosynthetic capacity of wheat,increase photosynthetic products,improve the utilization rate of light energy,promote glycolysis,reduce the accumulation of reactive oxygen species,and enhance stress resistance.The gluconeogenesis was inhibited,the ability of sucrose to decompose into fructose decreased,and trehalose synthesis decreased.8.The DEGs of high CO₂ concentration were compared with those of normal CO₂ concentration under drought conditions at 23 day after anthesis.It was found that the genes encoding INV,sucrose synthase（SUS）,subunit I of optical system,protein II of optical system,cytochrome b6,Fd,LHCB,6-phosphate fructose kinase-1（PFK1）,fructose diphosphate aldolase（FBA）,ascorbate peroxidase（Apx）,SOD,catalase（CAT）,HSPs and other related genes were up-regulated.Genes encoding hexokinase（HK）,fructose-1,6-diphosphate phosphatase（FDP）,glutathione S-transferases（GSTs）,phenylalanine ammonia lyase（PAL）and peroxidase（POD）were down-regulated.It indicated that high CO₂ concentration could improve the ability of sucrose to decompose into glucose and fructose,enhance the ability to synthesize starch,enhance photosynthetic capacity,improve light energy utilization,and increase the accumulation of soluble sugar and the synthesis of chlorophyll,reduced the oxidative damage and enhanced the stress resistance under drought conditions.9.The DEGs of drought compared with those of irrigation were up-regulated under the condition of high CO₂ concentration at 23 day after anthesis.It was found that the genes encoding INV,SUS,trehalose 6-phosphate phosphatase（TPP）,1,4-α-glucan branching enzyme（GBE）,starch synthase（SS）,light system I subunit,light system II protein,cytochrome b6,Fd,LHCB,HK,PFK1,FBA,pyruvate decarboxylase complex（PDHC）,aconitinease（ACO）,malate dehydrogenase（MDH）,HSPs and other related genes were upregulated.The genes encoding pyruvate kinase（PK）,GSTs,Apx,SOD,PAL and POD were down-regulated.The results showed that drought could enhance the ability sucrose to decompose into fructose and glucose,enhance the ability to synthesize starch,promote gluconeogenesis,reduce the oxidative damage of leaves,and promote the accumulation of soluble sugar and the synthesis of chlorophyll inhibited glycolysis,increased accumulation of reactive oxygen species,peroxidized membrane lipids,reduce stress resistance under high CO₂ concentration on wheat.10.The DEGs of drought compared with those of irrigation were analyzed under normal CO₂ concentration at 23 day after anthesis,and it was found that the genes encoding GBE,LHCB and light system II proteins were up-regulated.The genes encoding TPS,TPP,α-ketoglutarate dehydrogenase complex（OGDC）,GSTs,Apx and other related genes were down-regulated.The results showed that drought could enhance the ability of starch synthesis and photosynthetic capacity,and improve the utilization rate of light energy under the condition of normal CO₂ concentration.The ability of sucrose to decompose into fructose,trehalose synthesis,stress resistance and TCA cycle weakened,the speed of scavenging active oxygen slowed down,active oxygen accumulation increased,and stress resistance decreased.