Mapping And Transcriptome Analysis Of Key Genes Associated With Accumulating Anthocyanins In Peanut Testa

Peanut is one of the most important oil crops in China,which providing important source of edible oil and protein for people.There are several different testa colors of peanut including white,pink,black?or dark purple?,etc.The testa color of the traditional peanut varieties are pink and red,few varieties have black testa.The peanut with black testa is rich in anthocyanins,which are beneficial to human health.Peanut with black testa is more and more favored by consumers.Therefore,it is of great significance to reveal the genetic mechanism and important genes controlling in anthocyanin biosynthesis in peanut testa which will be help for breeding black peanut varieties using molecular breeding method.To identify the key genes controlling black testa in peanut,a mapping population was constructed by hybridization the black?YH29?and pink testa?WH10?cultivars.The gene controlling black testa was mapped on chromosome 10 through QTL-seq together other methods.A SNP marker tightly linked to black testa was developed which lead to identifying a potential candidate gene.The main results of the paper are as follows:1.Phenotypic analysis showed that WH10 is a peanut varietiy with pink testa,and YH29 is a peanut variety with black testa.In addition,YH29 also showed more purple coloration in the leaflets,flower,vasculature and petiole.In YH29,the content of anthocyanin in these tissues was higher than that in WH10.However,there was no difference in the color of cotyledons.2.Genetic analysis showed that all F1 hybrids of WH10?maternal parent?and YH29?male parent?were pink seed coat,which was consistent with the maternal parent.The color of the young leaves and flowers and the F2 seed coat of F1generation were lavender,which was an intermediate type between the two parents,indicating that the seed coat was developed by the plant cover and the seed coat color was determined by the mother gene.The statistical results of F2 seed coat color showed that the black seed coat:intermediate type:pink seed coat was 1:2:1,which was consistent with the separation ratio controlled by single gene.3.Through whole-genome resequencing-based QTL-seq,the major gene controlling black testa was mapped on chromosome 10 at a region between108-112.7Mb.A total of 12 SNP markers were developed with in this region.Among them,seven SNP markers showed polymorphism between parental lines,and further tested in the 57 F₂ individuals with extremely black or pink testa.We found that SNP marker pTesta1089 was closely linked with the trait of black tasta.4.Gene annotation of chromosome 10 showed that R2R3-MYB transcription factor gene?Ahy.J3K16K?is 2.9 kb downstream of the SNP marker pTesta1089.Ahy.J3K16K was highly expressed in the YH29 to compare with that WH10,implying that Ahy.J3K16K might be the key gene related to black testa.5.Comparative transcriptome analysis showed that five genes encoding key enzymes of anthocyanin synthesis were up-regulated,while,some genes related with competing for the same substrates with anthocyanin synthesis were down-regulated in YH29,suggesting that the co-expression of these genes may be the key factor of high anthocyanin accumulation in black testa cultivar.Conclusion:In this study,black testa controlling gene of YH29 was mapped in a4.7 Mb region?108-112.7Mb?of chromosome 10 and closely linked to SNP marker pTesta1089.The SNP marker pTesta1089 can be used for breeding black peanut varieties using marker-assisted selection?MAS?method.In addition,Ahy.J3K16K encoding a R2R3-MYB transcription factor gene might be the key genes controlling black testa of YH29.However,the expression regulation of Ahy.J3K16K need to be further studied.The present study provided a reference for further studying the molecular mechanism of anthocyanin synthesis in peanut and breeding new peanut varieties with high anthocyanin content.