Research On The Effects Of High Temperature Stress On Starch And Protein Content Of Wheat Grains

Wheat quality are mainly affected by grain protein content and starch content, high temperature stress can affect the yield and quality of wheat.Therefore, the study of the effect of high temperature stress on starch and protein content of wheat grains is of theoretical significance to explore the stability of wheat quality and the genetic improvement of wheat quality traits.In this study, Tags For Relative And Absolute Quantitation Isobaric (iTRAQ) was adopted to analyze the changes of protein expression profile of different wheat cultivars under high temperature stress. A genome-wide association analysis (GWAS) using natural population was applied to study SNP markers associated with grain starch content and grain protein content under high temperature stress.In the natural population, thermal stability on quality traits of varieties were screened through the thermal index of grain starch content and grain protein content in wheat.The main results were as follows:(1) Using the wheat varieties (lines) Jing 411, Gaocheng 8901, Nongda 4503, Nongda 3753 and 6040 as materials,high temperature was treated at filling stage. Then we found the grain weight and the grain plumpness were dropped under high temperature stress, but there was no change on grain length.Under high temperature stress, the flour of Jing 411 and Gaocheng 8901 had significantly increased albumin content and protein content, meainwhile SDS-sedimentation value and starch content decreased, these results showed that high temperature stress had a significant effect on wheat quality.(2) Using Jing 411 and Gaocheng 8901 as materials, Tags For Relative And Absolute Quantitation Isobaric (iTRAQ) was adopted to analyze the changes of protein expression profile of wheat grain under high temperature stress,indicating that there were 256 and 207 proteins expressed differentially in Jing 411 and Gaocheng 8901 respectively, including growth and metabolism proteins,energy metabolism proteins, processing and storage proteins, defense-related disease proteins,signal transduction, unknown function proteins and hypothetical proteins,revealing that high temperature had great influence on many metabolic pathways at filling stage. GO enrichment analysis suggested that differentially expressed proteins in Jing 411 and Gaocheng 8901 under high temperature stress mainly involved in response to stimulus, abiotic stress response and stress response.KEGG pathway annotation in Jing 411 and Gaocheng 8901 showed that high temperature stress mainly participated in protein synthesis pathway in the endoplasmic reticulum as well as starch and sucrose metabolism.Protein interaction network displayed that there were 8 differentially expressed proteins could form a interaction network in Jing 411 and 5 differentially expressed proteins in Gaocheng 8901,of which 3 differentially expressed proteins(including CBL1,EGR3 and BRIl)could form the same interaction network.(3) A natural population including 200 wheat varieties (lines) growing in main winter wheat areas in China,and GWAS found 13 SNPs associated with protein content under normal circumstances,mainly concentrated on 7A;66 SNPs associated with protein content were found under high temperature stress, mainly concentrated on 6B, of which 4 SNPs are the same, mainly concentrated on 7A. Under normal circumstances,11 SNPs associated with starch content were found,mainly concentrated on 2D; under high temperature stress,60 SNPs associated with starch content were found,mainly concentrated on 6B.At the same time,17 SNPs associated with the thermal index of grain protein content were found, mainly concentrated on 2A; 49 SNPs associated with the thermal index of grain starch content were found, mainly concentrated on 6B,of which 14 SNPs were same,distributed on 2A and 3A chromosomes. Taking the thermal index of grain starch content and grain protein content in wheat as selection criteria,if S<l,they were heat resistant varieties,if S>l,they were heat sensitive varieties,as a result,7 heat resistant varieties and 8 heat sensitive varieties were selected. Combining the external morphology of heat resistant varieties and heat sensitive varieties,the feasibility to screen thermal stable varieties by the thermal index of grain starch content and grain protein content in wheat was well demonstrated.