Effect Of ω-gliadin Genes On Quality In Wheat And Genome-wide Association Study Of Its MRNA Expression

Wheat is one of the main grain crops in China.At present,the main goal of wheat breeding is to improve its processing quality on the basis of increasing the yield.Gliadin accounts for about 50%～60%of the total gluten content,which determines the viscosity and extensibility of dough.ω-gliadin,as an important component of gluten,is closely related to wheat quality.So in this study,we used degenerate primers and PCR techniquethe to clone ω-gliadin genes in Zhengmai 369,which would enrich the genetic information of omega-gliadin.In order to explorer the effect of ω-gliadin genes on wheat quality,we constructed nature population with 120 materials and mRNA expression of ω-gliadin genes in each material was obtained by RNA-seq technique and the relationship between ω-gliadin gene expression and wheat quality was analyzed.At last,we used 660k SNP chip to do genome-wide association study of mRNA expression of ω-gliadin genes,in order to find maker-trait association sites,which could provide a theoretical basis for the improvement of wheat quality traits.Fifteenco-gliadin genes(ZM369-1～15)were cloned from wheat variety Zhengmai 369.ZM369-1 and ZM369-15 were true genes,and ZM369-2～14 were pseudogene.Among them,ZM369-15 belongs to the unreported ARP type,in addition,there was an insertion of cysteine residue in the repetitive region.No amino acid sequence with high similarity to ZM369-1 and ZM369-15 was found in NCBI database,so we presumed them to be new co-gliadin genes.Phylogenetic tree analysis showed that 15 cloned genes had a relatively close evolutionary relationship withω-gliadin gene sequences of T.urartu and Aegilops tauschii Coss and combined with their types,we indicated that they were originated from A or D genome.Most of theω-gliadin genes from the same genome could form relatively concentrated branches,which indicated that ω-gliadin genes had certain genomic specificity.ω-gliadin genes of the same type could form relatively concentrated branches,suggesting that the type of ω-gliadin genes might be related to evolution.mRNA expression of co gliadin gene in 120 samples was analyzed by RNA-seq.The results showed that 36 of 73 genes as reference sequence could be expressed in at least 1 material.There was significant difference in mRNA expression among different ω-gliadin genes in population.The average mRNA expression of KC716067 and KM879350 was 17.3 and 7.92 respectively the highest.The average mRNA expression of KM879346 was 0.03 the lowest,and only 15 genes were expressed in a few materials(≤10).The mRNA expression of ω-gliadin genes was different among different varieties,and the expression of ω-gliadin gene mRNA was the highest in Beijing 411 and Baofeng 10-82.The correlation between ω-gliadin genes of the same type and quality was the same.ω-gliadin gene of ARQ/E type had significant negative effects on cohesion characteristic index PM,A4 and A5;some genes had significant negative effects on gluten content,water absorption and the cohesion characteristic index BEM;KF412580 had significant negative effects on farinograph quality number,and KC716065 had significant negative effects on the cohesion characteristic index A1.Partial co-gliadin genes of SRL type had significant positive effects on cohesion characteristic index PMT,AM and A3;KM879356 had significant positive effects on wet gluten content,and KR077925 had significant positive effect on wet gluten content,dough stability time and farinograph quality number and had a significant negative effect on the dough softening degree.ZM369-15 of ARP type had significant positive effect on wet gluten content,AM,PM and A5,and KM879350 of TRQ type had significant positive effect on PMT.ω-gliadin genes had no significant effect on flour whiteness,gluten adhesion characteristic index A2 and dough development time,co-gliadin gene of ARH,GRL and SRM types had no significant effect on wheat quality.The mRNA expression in 120 varieties of twenty ω-gliadin genes significantly related to quality were analyzed by genome-wide association.Fifty-eight SNP markers related to the mRNA expression of co-gliadin genes were located on 18 chromosomes.It can explain 25.38%-46.71%phenotypic variation.For differentω-gliadin genes,the number and chromosome distribution of the marker sites related to the expression of mrna were not exactly the same.Eight polymorphic SNP markers related to the mRNA expression of ω-gliadin gene were identified on 1B,3A,3B and 3D chromosomes,which could explain 25.38%～46.71%phenotypic variation.