Insights Into The Physiological Mechanism Of Wheat In Response To High Temperature Stress: Perspective Of Lipidomics

Wheat(Triticum aestivum L)is one of the major food crops in China.During the growth and development of wheat,abiotic stresses such as high temperature and drought often accompany the growth of wheat,which affect the quality and yield of wheat.During the long evolutionary process,wheat has gradually evolved a series of mechanisms to respond to stresses,but the response to high temperature stresses varies among cultivars.In this experiment,the physiological indexes,yield and quality differences of two strong wheat cultivars with different high temperature resistance,Xinmai 26(XM26)and Zhengmai 7698(ZM7698),were investigated under temperature(high temperature)stress by setting high temperature stress and normal temperature treatments at flowering period in the artificial climate chamber of Henan Agricultural University from 2021 to 2022 using potted plants.The differences in lipid metabolism of the 2 cultivars under high temperature stress were also analyzed using lipidomics.The main findings were as follows.1.Differences in antioxidant system responses of two different heat-tolerant wheat cultivars under high temperature stressChanges in antioxidant enzyme activities are an important mechanism for plants to cope with stress.The malondialdehyde(MDA)and hydrogen peroxide(H2O2)contents of the leaves of the two cultivars increased under high temperature stress;where after 3 and 7 days of stress,the leaf MDA of XM26 was 49.90% and 58.74% higher than the control,and ZM7698 was 32.16% and 16.96% higher than the control,respectively.The MDA content of ZM7698 leaves decreased by 26.95% and 40.06%,respectively,compared with XM26.At 3 and 7 days of high temperature stress,the H2O2 content of XM26 flag leaves increased by 31.43% and 26.93%,respectively,compared with its normal temperature;while the corresponding H2O2 content of ZM7698 increased by 17.06% and 11.70%,respectively;indicating that the increase in MDA and H2O2 content of heat-tolerant variety ZM7698 under high temperature stress was less than that of sensitive variety XM26.The SOD activity of XM26 decreased by 10.53% and 37.29% compared to its corresponding normal temperature at 3 and 7 days of high temperature stress,while the SOD activity of ZM7698 increased by 34.42% and 31.84% compared to normal temperature;and the enzyme activity of ZM7698 was higher than that of XM26 under the corresponding treatment.The POD activity of XM26 and ZM7698 decreased by 35.30% and 16.33%,respectively,and CAT activity decreased by 41.47% and 6.13%,respectively,compared with their control.It showed that the heat-tolerant variety had higher antioxidant enzyme activity and the decrease in activity under high temperature stress was lower than that of the heat-sensitive variety.2.Differences in yield and its components between two different heat-tolerant wheat cultivars under high temperature stressAfter high temperature stress,the yield of ZM7698 decreased less than the control than the corresponding decrease of XM26;among them,the yield of XM26 decreased 158.25% after high temperature stress compared with the control,while the yield of ZM7698 variety decreased 124.90%.The analysis of the changes in the number of spikes,the number of grains and the weight of 100 grains showed that the number of spikes,the number of grains and the weight of 100 grains of XM26 decreased by 48.68%,29.95% and 26.72%,respectively,compared with their normal temperatures,while the number of spikes,the number of grains and the weight of 100 grains of ZM7698 decreased by 31.48%,27.04% and 11.06%,respectively,compared with their normal temperatures under high temperature.It showed that the number of spikes,number of grains and grain weight of heat-tolerant cultivars decreased less than that of sensitive cultivars,thus reducing the yield decline under high temperature stress.3.Differences in protein and its components between two different heat-tolerant wheat cultivars under high temperature stressHigh temperatures caused a significant increase in the content of protein and its fractions and a decrease in the sedimentation value in both wheat cultivars.The protein content and protein fractions of both XM26 and ZM7698 increased significantly after stress compared to normal temperature growth,and the effect of high temperature on alcoholic and glutenic proteins was greater than that of clear and globular proteins,where the increase in protein content of XM26 was greater than that of ZM7698,and the increase in the four protein fractions of ZM7698 was greater than that of XM26,due to the difference in the increase in alcoholic and The increase of the four protein fractions of ZM7698 was greater than that of XM26.4.Differences in leaf lipid metabolism between two different heat-tolerant cultivars under high temperature stressThe high temperature reshaped the lipid composition of the two cultivars,and the proportion of DGDG and PI in the heat-tolerant variety increased after high temperature stress,while the proportion of DGDG and PI in the sensitive variety decreased;among them,the DGDG and PI in XM26 leaves decreased from 29.20% and 15.08% at normal temperature to 25.40% and 14.97% under high temperature stress,respectively;while the DGDG and PI in ZM7698 leaves DGDG and PI in ZM7698 leaves increased from 25.11% and 14.26% to 30.98% and 18.71%,respectively.The lipid unsaturation of SQDG and PA of heat-resistant cultivars decreased significantly under high temperature stress,while the lipid unsaturation of SQDG and PA of heat-sensitive cultivars increased significantly,with SQDG unsaturation of XM26 increasing from 4.12 to 4.56 and PA unsaturation increasing from 2.13 to 2.52 under high temperature stress,and SQDG unsaturation of ZM7698 decreasing from 4.44 to 4.29,and the unsaturation of PA decreased from 2.32 to 2.04.The increase in MGDG and PE lipid unsaturation under high temperature stress was lower than that of the corresponding sensitive cultivars.The St E/Si E of heattolerant cultivars was lower under high temperature stress,with 2.57 and 2.18 for XM26 and 2.31 and 2.08 for ZM7698 under normal and high temperature stress,respectively.The results suggest that heat-tolerant cultivars can improve their resistance to high temperature stress by changing the composition ratio of the above lipid components and reducing lipid unsaturation.