Effects Of ABA On Sugar Metabolism And Expression Of Antifreeze Genes Of Winter Wheat

The Triticum aestivum Dongnongdongmai1cultivar has an85%winter survival rate and isthe only winter wheat variety grown in Heilongjiang Province (minimum temperature up to-30℃).The T. Aestivum Jimai22cultivar is widely planted in northern China, also has a strong coldresistance, but cannot survive in the cold winter temperatures in Heilongjiang Province. In thisstudy, both winter wheat were used as test materials, and the effects of exogenous ABA on sugarmetabolism and expression of antifreeze genes at low temperature stress were discussed in theseedling stage and wintering stage, and to understand the physiological and molecular basis forexogenous ABA regulating winter wheat sugar metabolism and expressions of antifreeze genes,and it will provide new ideas for revealing exogenous ABA improving cold hardiness of winterwheat. Dongnongdongmai1is the only winter wheat varieties that can be grown in the alpineregion of Heilongjiang Province, and it is typical and representative; Low temperature treatingwheat seedlings in room was adopted in studying cold resistance of winter wheat at home andabroad, but in this study, stimulated low temperature and natural low temperature in the field werecombined, and it is closer to the actual production; In this study, physiological and biochemicaltechnology and molecular biology techniques experimental method were used to study the ABAregulating winter wheat cold tolerance from the point of sugar metabolism and cold tolerance geneexpression at first time to overall grasp the source and path of the carbohydrate, and clarify theeffects of the ABA on plant energy flows, the penetration level, the energy metabolism undersignal effect and cold tolerance gene regulation process, and will provide theoretical basis forantifreeze mechanism of winter wheat, and make an important contribution to the improvement ofthe cultivation of winter wheat in the northern alpine region in the end. The results are as follows:1. Effect of exogenous ABA on winter sugar metabolism in seedling stage at low temperaturesExogenous ABA promoted the accumulation of soluble sugar、sucrose content and fructosecontent to improve the soluble sugar content in the leaves of Dongnongdongmai1with strong coldresistance in seedling stages at low temperatures, and exogenous ABA promoted the accumulatonof sugars in the underground stems above0℃; Accumulation of sugars in the leaves andunderground stems of Jimai22was not promoted by exogenous ABA. Starch accumulation wassuppressed by exogenous ABA in the leaves and underground stems of the two wheat or the differences between control and ABA treatment was not significant. Exogenous ABA promoted theexpression levels of TaRBC、TaFBP、TaPRK、TaUGP、TaSAInv、TaSPS、TaPK、TaG6PDH、TaTPT and TaSuT in the leaves and underground stems of Dongnongdongmai1to different extent,and these genes are involved in the carbon fixed, synthesis and degradation of sucrose、glycolysis、pentose phosphate pathway and sugar transport. But, some genes such as TaAGP, TaPDand TaHxK were down-regulated by exogenous ABA in Dongnongdongmai1; Most key enzymesgenes of sugar metabolism were suppressed by exogenous ABA in Jimai22.2. Effect of exogenous ABA on winter sugar metabolism in wintering stage at low temperaturesIn wintering period, more soluble sugars, sucrose and fructose were accumulated in leaves andtillering nodes of ABA treated seedlings of the two wheat cultivars, especially in the winteringorgan tillering nodes. More carbohydrates were accumulated in cold-resistant wheat cultivarDongnongdongmai1than in cold-sensitive wheat cultivar Jimai22. Exogenous ABA improved theaccumulation of starch in the two tissues of Dongnongdongmai1and the leaves of Jimai22, butthe accumulation in the tilleringnodes of Jimai22was not obviously effected by exogenous ABA.Exogenous ABA promoted the expression of TaRBC、TaFBP、TaPRK、TaUGP、TaAGP、TaSAInv、TaSS、TaSPS、TaPK、TaH xK、TaPFK、TaPD、TaG6PDH and TaSuT gene expression in the leavesand tillering nodes of Dongnongdongmai1and Jimai22to different extent, but a greater extentwas showed in the Dongnongdongmai1than Jimai22. Exogenous ABA significantly promotedexpression of TaPRK, TaUGP, TaSPS, TaSAInv, TaPD, and TaPFK gene in leaves of two varietiesof winter wheat, and TaTPT only upregulated in the leaves of Dongnongdongmai1. ExogenousABA promoted sucrose accumulation and also promoted the decomposition of sucrose, but theaccumulation was greater than decomposition, while the SPS and SS played a role in terms ofsucrose accumulation, and UGP played important role in sucrose accumulation and decompositionat the same time, acid invertase and alkaline invertase enzymes played roles in the decompositionof sucrose; ABA treatment improved the glycolytic metabolic enzyme pyruvate kinase, hexokinaseand phosphofructokinase activity to varing degrees in the leaves and tillering nodes of the twovarieties of wheat, especially in the minimum temperatures-25℃,enzyme activities decreaseswere inhibited by exogenous ABA, there by slowing the injury of temperature drops to winterwheat, but this effect was even more marked in cold-resistant wheat cultivar Dongnongdongmai1than in cold-sensitive wheat cultivar Jimai22, and the acetoneacid kinase activity was inhibited byABAin the tillering nodes of Jimai22.3. Correlation analysis between the sugar content and the expression of key enzyme genes of andenzyme activity of sugar metabolismThe correlation between sugar content and gene expression of sugar metabolism was more prevalent in ABA treated group. There was a certain consistency regulation on sugar content andsugar metabolism gene expression by exogenous ABA. But the correlation between the sugarcontents and sugar metabolism gene expression in control and ABA treated group were not entirelyconsistent at seedling stage and wintering period, this indicated that there was a complexrelationship between the accumulation of carbohydrate and sugar metabolism gene expression.Correlation analysis between the sugar content and the activities of sugar metabolism in winteringstage indicated that the correlation was more prevalent in ABA treated group.The degree ofcorrelaton between sugar content and sugar metabolic enzymes activites was higher than thecorrelation between sugar content and sugar metabolism gene expression in leaves of the twowheat cultivars. Exogenous ABA affected sucrose metabolism and respiratory metabolism troughregulating the sucrose metabolism enzyme activities and respiratory metabolism related enzymesactivities in winter wheat at low temperatures. Surose metabolism enzymes as well as respiratoryMetablosm enzymes were affected and coordinated each other and regulated the sucrosemetabolism and respiratory metabolism intricately.4. Effect of exogenous ABA on expression of antifreeze genes at low temperaturesExogenous ABA affected antifreeze genes expressions of winter wheat by ABA-dependentsignaling pathways, and these effects were more obvious in in cold-resistant wheat cultivarDongnongdongmai1than in cold-sensitive wheat cultivar Jimai22. In seedling stage, at lowtemperatures, exogenous ABA promoted the expressions of TaCBFIVd-D22and TaMYB80genesbefore8h low temperature stress, and promoted the expressions of TaWabi5and TaWrab17genesin leaves of Dongnongdongmai1, and exogenous ABA promoted the expression of TaMYB80、TaWabi5and TaWrab17genes, and promoted the expression of TaCBFIVd-D22genes before8hlow temperature stress in underground stems of Dongnongdongmai1; In the leaves of Jimai22, theexpression of TaWabi5was upregulated by exogenous ABA at0.5h of low temperature stress, andthe expressions of TaCBFIVd-D22and TaMYB80were upregulated before8h low temperaturestress, the expression of these four genes were all inhibited by exogenous ABA in undergroundstems of Jimai22. In wintering stage, exogenous ABA promoted the expressions of TaMYB80、TaWabi5and TaWrab17genes and promoted the expression of TaCBFIVd-D22above0℃in theleaves of Dongnongdongmai1, and the expressions of TaCBFIVd-D22、TaMYB80and TaWrab17genes were promoted by exogenous ABA and the expression of TaWabi5gene was promoted byexogenous ABA as well in leaves of Jimai22; In tillering nodes of Dongnongdongmai1and Jimai22, exogenous ABA promoted the expression of TaCBFIVd-D22, and also pomoted the expressionof TaWabi5gene above0℃, and the expressions of TaMYB80and TaWrab17were all inhibitedby exogenous ABA in tillering nodes of Dongnongdongmai1, while in tillering nodes of Jimai22,exogenous ABA promoted the expression of TaWrab17, and inhibited the expression of TaMYB80. There were some impacts of exogenous ABA on cold resistance genes in the ABA-independentsignaling pathways as well, and expressions of these genes were promoted by exogenous ABA to acertain extent.