Exogenous Nitric Oxide Effect On Fructan Anabolism And Gene Expression In Wheat To Chilling Stress

Low temperature is one of the most important environmental factors affecting plant growth anddevelopment, and the adaptability of plants to low temperature has been a worldwide research project. Thisstudy was to investigate the effect of exogenous nitric oxide (NO) on fructan anabolism and fructanbiosynthesic enzymes (FBEs) expression in seedlings leaves of two wheat (Triticum aestivum L.) cultivars,semi-winter wheat Zhoumai18and weak spring wheat Yanzhan4110, under4°C. The seedlings of twowheat cultivars were subjected to different concentrations of sodium nitroprussiate (SNP) for0,24,48, and96h. By the research on the molecular mechanism of NO effect on wheat resisting low temperature stress,we strive hard to make certain efforts to resolve this important issue of wheat chilling injuries, providing atheoretical basis for food security. The main findings are as follows:1. To chilling stress, the soluble sugar content and chlorophyll a/b ratio showed the certain extent risein seedlings leaves of the two wheat cultivars, chlorophyll a, b and carotenoid contents showed a downwardtrend, and RWC in Zhoumai18declined significantly. Exogenous NO could induce fructose, glucose, lowDP fructan, total soluble sugar, chlorophyll a, b and carotenoids contents in the two wheat cultivars, andsucrose and high DP fructan contents in Zhoumai18, and brought RWC down in the two wheat cultivars.2. To chilling stress, fructans (including DP3and DP≥4) content have a certain degree of increase inseedlings leaves of the two wheat cultivars. Low concentration (0.075mmol·L^-1) of NO could inducefructans content in the two wheat cultivars; high concentration (0.125mmol·L^-1) of NO could also inducefructans content significantly in Zhoumai18, but showed some toxic effects to Yanzhan4110. It could bedemonstrated that the appropriate concentration of exogenous NO could induce fructans content in the twowheat cultivars under low temperature stress, resisting external low-temperature environment to reduce lowtemperature injury.3. To chilling stress, fructan: fructan1-fructosyltransferase (1-FFT, EC:2.4.1.100) activity remained ata significantly lower level than FS (including sucrose: sucrose1-fructosyltransferase (1-SST, EC:2.4.1.99)and sucrose: fructan6-fructosyltransferase (6-SFT, EC:2.4.1.10)) activity in seedlings leaves of the twowheat cultivars. High concentration of NO significantly induced FFT activity in Zhoumai18and FS activity in Yanzhan4110. It could be demonstrated that FFT activity in semi-winter wheat cultivar and FSactivity in weak spring wheat cultivar could be induced by high concentration of NO, contributing tofructan accumulation in seedling leaves to reduce low temperature injury.4. To chilling stress, FBEs gene expression at the transcriptional level was improved in seedlingsleaves of the two wheat cultivars. Exogenous NO could regulate the gene expression at this level infollowing ways: except that1-SST and6-SFT gene expression in Zhoumai18were inhibited by highconcentration of NO,1-FFT and Yanzhan4110' three FBEs gene expression were all induced by exogenousNO. It could be demonstrated that exogenous NO could take part in regulate FBEs gene expression at thetranscriptional level, and the appropriate concentration of exogenous NO could induce FBEs geneexpression in the two wheat cultivars under low temperature stress.5. In Zhoumai18, exogenous NO induced the synthesis of sucrose which provided rich substrate forfructan synthesis, and induced FFT gene expression to promote FFT enzyme activity greatly, so that highDP fructans accumulated abundantly in plant to enhance the resistance to external adverse environment.However in Yanzhan4110, the ability of fructans generated internally was poor. Sucrose was not inducedby exogenous NO but low temperature, and was significantly associated with fructans content. Byinference, the synthesis of fructans may depend on high concentration of sucrose in wheat.There has been less reports on exogenous NO reduces chilling injuries by inducing the accumulationof fructans in wheat. It can be concluded from this study that the appropriate concentrations of exogenousNO will induce FBEs gene expression in plants to promote the activities of FBEs. Thus large amounts offructans are accumulated in young leaves, to make seedlings less susceptible to low temperature stress, andto improve the cold resistance of winter wheat.