Mapping And Transcriptome Analyses Of Genes Involved In Anthocyanin Biosynthesis Of Blue Wheat

Wheat?Triticum aestivum L.?is among the most extensively cultivated crops worldwide and is a staple food consumed by one-third of the world's population.Wheat not only provides humans with basic nutrients of carbohydrates,proteins,vitamins,but also contains significant levels of biologically active dietary substances,such as carotenoids,flavonoids and phenolic acids.The interest in wheat genetic resources with different grain color has recently increased.Differences in grain color are caused by the presence of polyphenols,tannins,anthocyanins and carotenoids.The important characteristic of blue colored wheat is that it contains significantly increased levels of natural anthocyanin compounds,while common red and white wheat has very few to low levels of it.These substances have antioxidant activity and are useful for the production of functional foods with positive effects on consumers'health.Furthermore,these anthocyanin pigments can be concentrated by dry milling and fractionation processes to produce fractions with high anthocyanin levels.Understanding the anthocyanin biosynthesis pathway in blue wheat could be employed for the breeding of varieties accumulating a higher number of relevant genes,which would allow to increase the content of health-promoting substances.In this research,initially blue grain color development and inheritance was observed for the background knowledge.To understand the genetic control of blue trait in wheat,two approaches were adopted.At first high throughput SNP mapping was carried out to detect the location of the blue trait in wheat using newly developed wheat 90k iSelect SNP array comprised of nearly 90,000 gene-associated SNPs.Then the Comparative transcriptome analysis of blue and non-blue wheat grain samples were carried out to identify the candidate genes controlling the wheat blue grain trait.1.Grain Color Development and Segregation of Blue WheatAnthocyanins are one of the most valuable antioxidants,which showed the fabulous importance to human health.Blue grained wheat has been identified as high anthocyanin containing cereal compared to other colored wheat varieties.Little is known about the inheritance of the blue grain traits including their genome location.In this experiment,we observed the grain color development and the segregation of blue wheat.The blue color development of wheat grains started at the mid grain development stage of 20 days post anthesis?dpa?and completed within 26 dpa.Segregation pattern of blue wheat was studied using an F₂ population derived from blue and white wheat found the segregation is not followed the simple Mendalian inheritance.The different color intensities of blue wheat grains may be due to genetic dosage effect and the effect of minor genes.The main reason for the huge variation in the segregation of blue and white seeds in the same spike of the blue population is the effect of xenia.Several other genetic and environmental factors also effect for the blue trait in wheat.These findings will be helpful to identify the genetic basis of blue aleurone traits which will be utilized for further improvement of the blue wheat crop.2.High throughput mapping and transcriptome analyses revealed the controlling gene of blue wheat grainsThe important characteristic of blue grained wheat is that it possesses a high amount of natural anthocyanin compounds which show high antioxidant activity while normal commercial wheat varieties have minute amount of it.With increasing universal attention over food related health issues,the demand for foods provide nutrients,energy and health benefits simultaneously are growing rapidly.At present,major genes related to several colors of wheat have been identified.However,the major genes or control mechanism of anthocyanin biosynthesis in blue grained wheat is still unrevealed.Hence,combining the information of the chromosomal location of blue grain trait,and genes screened out from transcriptome analysis,we attempt to find the pivotal genes regulating blue trait in wheat.SNP genotyping was carried out in an F₂ blue and white wheat population using 90k iSelect Infinium assay.The result showed that blue grain was controlled by a gene/locus located between two SNP markers of IWB 18525 and IWB 16381 on 4D chromosome.Comparative transcriptome analysis of two blue and 6 non-blue wheat grain samples were carried out to identify the candidate genes controlling the wheat blue grain trait.A total of 126,792differentially expressed genes?DEGs?was found in blue and white wheat pools.Forty structural DEGs related to anthocyanin biosynthesis had significant expression differences between blue and non-blue samples.Among them,12 DEGs expressed only in blue grain samples while of the identified transcription factor DEGs,only 2 were specific to blue wheat.These candidate genes were distributed in different chromosomes.Among them,only two F3'5'H genes located in 4D?Traes₄DL₂7C195FDE,Traes₄DL₅A3D8F519?that consistent with the location results we performed in SNP genotyping.Meanwhile,F3'5'H is the main enzyme direct to the production of delphinidin compounds which give the blue coloration.This suggested that two genes encoding F3'5'H in 4D chromosome preferentially account for the blue pigmentation in wheat.The blue grain trait,caused by structural genes in the blue wheat,which gives a different mechanism from purple pericarp phenotype that regulated by transcription factors.Further,our research provides useful clues to find out the translocated genes in a particular trait.