Effect Of Heat Stress On Starch Synthesis And Protein Accumulation In Triticale Grain At Filling Stage

Object: Starch is the main component of wheat grain,while the protein fraction is important for determining grain quality.Both genotype and environment influence Triticale,starch accumulation was reduced when endosperms developed at elevated temperatures.Heat stress in the sublethal range during the grain filling stage inhibited the yield of wheat by reducing single grain weight.also it may result in modification of protein deposition and reduce end use quality.Therefore,the study of the effect of heat stress on starch and protein content of triticale grain is of theoretical significance to explore the stability and heat tolence of triticale quality.Methods: Four triticale varieties were used in field experiment.Plants were initially grown in the field environment and were used with a heat stress treatment in the field by plastic sheds for the heat stress(HS)treatment.HS began from the 5 day after anthesis(DAA)and ended at the 15 DAA,with a high temperature of 35±2°C for six hours from 12:00 to18:00,after which the plants were returned to the field environment.The starch synthesis,protein synthesis,and related enzymes activities were roundly investigated,and the results elucidated the relationship between starcha and protein component and related enzymes activities,and the physiological and chemical mechanism of Heat tolence effects on starch quality formation.The main results and conclusions:1、The thousand kerner weight and volume wight density of 4 triticale varieties(lines)decreased significantly after heat stress regimen.Thousand kerner weight in dropped to: 5.95%~22.67%;volume weight fell by 3.38% ~ 9.49%;two years consistent results.Comparing two years results,4 cultivars were affected by high temperature was senstivity degree: XXHM 5 > KuoFun1 > XXHM3> XXHM42、Heat stress after anthesis reduced the various indicators of starch formation significantly of hexaploid triticale.5-14 days after anthesis heat stress has the most affect of the starch and protein formation of hexaploid triticale,starch content decreased 7.66%~16.53% respectively to make four triticale varieties,amylose content decreased by 2.26%~8.61%.amylopectin decreased 8.02% ~ 22.10%.total starch accumulation decreased by 10.90%~35.62%.protein content increased in 3.42%~14.81%.total protein accumulation decreased by 3.49%~11.81%;The results showed that there was significant effect of heat stress on starch accumulation of wheat grain.High temperature remarkably reduced starch and protein accumulation at maturity.The total starch and amylopectin contents of heat stress treatments decreased markedly,Then the ratio of amylose to amylopectin in heat stress regimen was higher than that of control regimen.3、The content of starch and amylose and the activities of AGPPase,SSS and GBSS under heat stress were generally higher at the beginning of the grain filling stage and obviously lower during the day past anesisth 25~35d.with the exception of the activity SBE which were always higher under control tretments.The relationship between the changes of activities of SSS,SBE and the variation of starch accumulating rate was very close and so did the relationship between GBSS activity and the amylose content.4、Effect of heat stress on starch degradation metabolism in triticale kenerls at grain filling stage presented similar features:under HS alpha amylase were highter at control treatment and decreased the activity of beat amylase,it resulted in a rapid accumulation of intermediate poduct from starch and impaired successive degradation of intermediate product.which might restrict carbon and enery supply,reduce total starch content in triticale kenerl.5、The activities of GS,GOGAT,GOT,GPT were promoted under HS,yet decreased the 25~35DAA the activities of GS,GOGAT,GOT,GPT.The effects of heat stess after flowering period on GS and GOGAT activities showed the similar trend,with increasing at early grain filling stage and decreasing at late grain filling stage,and GOT and GPT activity showed the bimodal curve.6、during the grain filling stage the expression of genes related to starch biosynthesis were influenced by heat stress,Under HS there were 12 genes related to starch biosynthesis,9 genes were down-regulated(agpⅡ、gbssⅠ、gbssⅡ、sssⅠ、sssⅡ、sssⅣ、sbeⅠ、sbeⅡb),3 genes up-regulated(agpⅠ、sbeⅡa、sssⅣ);and there were 11 genes related to starch degradation metabolism,4 genes were down-regulated(bam1、bam2、bam3、bam4),7 genes were up-regulated(amy1、amy2、amy3、amy4、bam3、bam6、bam7).Among those 23 genes related to starch biosynthesis,7 genes(agpⅡ、gbssⅡ、sssⅠ、sssⅡ、sbeⅠ、bam1、amy3)were at high-expression level during grain-filling stage and play a important role in starch biosynthesis process.among those 7 genes,6 genes were down –regulated under HS(agpⅡ、gbssⅡ、sssⅠ、sssⅡ、sbeⅠ、bam1),1 genes(amy3)were up-regulated,It will make a serious restrain of starch synthesis.