Effects Of Nitrogen Metabolism And Storage Protein-related Gene Expression On Storage Protein Synthesis And Gluten Quality In Wheat

Wheat gluten protein has its unique properties of water holding,viscoelasticity,and foaming,which plays a decisive role in the strength,ductility,and air holding of the dough,and its quality directly determines the final edible quality of the dough.In this study,five wheat varieties with different gluten quality and four near-isogenic lines(NILs)of the HMW-GS alleles at Glu-B1 locus in the genetic background of xinong 1718 were used as materials to study the effects of nitrogen metabolism and storage protein synthesis-related gene expressions on wheat storage protein synthesis and gluten quality.The main results are as follows:(1)With the increase of gluten content,the content of disulfide bond(–S–S–)and?-sheet,and the density of network crosslinking increased in different wheat gluten.the gluten of xinong20 had the highest value,followed by xinong836,xinong979,zhoumai18,and xinong977.Contrastingly,the gluten of xinong977 had greatest surface hydrophobicity,free sulfhydryl group(SH)and?-helix content,followed by zhoumai18,xinong979,xinong836,and xinong20.The thermal analyses showed that the gluten from xinong20 had the highest values for the denaturation peak temperature(T_p)and degradation temperature(T_d),xinong 836 had the highest values for enthalpy of thermal transition((35)H),whereas those of xinong 977 are lowest.The gluten of Glu-1Bh(1,14+15,2+12)had the highest level of–S–S–content,Junctions density,Lacunarity,T_p,T_d,(35)H,dough development time and stability time,protein weakening,followed by Glu-1Bc(1,7+9,2+12),Glu-1Bb(1,7+8,2+12),and Glu1-Bd(1,6+8,2+12).However,the SH content,surface hydrophobicity,and weight loss exhibited the opposite trend.(2)During grain development,dynamic analysis of grain protein accumulation in wheat with different gluten quality indicated that the accumulation rate of gliadin in xinong20 and xinong979 was faster,and the contents of glutenin and glutenin macropolymer(GMP)in xinong20,xinong836,and xinong979 were relatively higher.At 40 days after anithesis(DAA),the highest gliadin content was found in xinong20,followed by xinong979,zhoumai18,xinong836,and xinong977;the content of glutenin and GMP from high to low ranked as xinong20,xinong836,xinong979,zhoumai18,and xinong977.There was no significant differences in the accumulation of gliadin among the four NILs during grain filling.However,there were differences in the accumulation of glutenin and GMP,where the highest were found in Glu-1Bh.At 34 DAA,the glutenin,GMP,and total protein contents were ordered by size as Glu-1Bh>Glu-1Bc>Glu-1Bb>Glu-1Bd.The observation of the resin sections structure showed that more abundant and larger protein bodies accumulated in the endosperm cells of Glu-1Bh from 10 to 16DAA,followed by Glu-1Bc,Glu-1Bb,and Glu-1Bd.(3)Grain protein synthesis is largely dependent on nitrogen metabolism.Xinong20 had higher glutamine synthetase(GS)and glutamate pyruvate transaminase(GPT)activities and amino acid contents in the flag leaves and grains than the other lines during grain development,followed by xinong836,xinong979,zhoumai18,and xinong 977.The expression level of genes related to nitrogen metabolism was consistent with the enzyme activity.During grain development,Glu-1Bh exhibited higher activities of GS and GPT,amino acid content,and gene expression related to nitrogen metabolism in the flag leaves and grains,followed by Glu-1Bc,Glu-1Bb,and Glu-1Bd.(4)The formation and accumulation of storage proteins are regulated by various essential genes and transcription factors(TFs)at different developmental stages.During grain filling,the expression levels of x/y-HMW,LMW-A/B/D,Ta GAMyb,Ta PBF,Ta SPA,Ta PDIL2-1,Ta PPIase,and Ta SUMO1 in xinong 20,xinong 836,and xinong 979 were significantly higher than that of zhoumai18 and xinong 977.Among four NILs materials,Glu-1Bh exhibited higher storage protein-related genes expression,followed by Glu-1Bc,Glu-1Bb,and Glu-1Bd.In summary,genes related to nitrogen metabolism and storage protein synthesis in wheat have important effects on storage protein synthesis and gluten quality,which provides a theoretical basis for improving and breeding wheat varieties with high gluten strength from the gene level of nitrogen metabolism and storage protein.