| Rice is one of the most important food crops in the world.It has been found that some rice is rich in a functional nutrient,?-aminobutyric acid(GABA).However,the current research on ?-aminobutyric acid in crops is mainly focusing on physiological characteristics and metabolic synthesis,there are few studies on the genetic laws of ?-aminobutyric acid content in crop grains.Therefore,it is of great significance not only to cultivate new rice varieties rich in ?-aminobutyric acid,but also to fully explore the germplasm resources of ?-aminobutyric acid-rich rice.Moreover,it can provide a theoretical basis for the genetic study of ?-aminobutyric acid content in crops.In this study,Ningnong black carp with low content of y-aminobutyric acid was used as the female parent and aminobutyric acid with high y-aminobutyric acid content as the male parent,and hybrid F1 was obtained.F2 and F2:3 families were obtained after selfing.A fine-targeted population consisting of 6162 F2 and F2:3 families was used as the experimental material,and the primary positioning results RM342 and RM515 were used as the upstream and downstream flanking markers to develop a new marker to determine the QTL locus of y-aminobutyric acid content in rice grains.The qGABA8 fine mapping was in the range of approximately 183 Kb between RM342 and G121.According to the rice genome annotation,29 predicted genes were found in this interval.The specific research results are as follows:1.This study used three SSR markers with high contribution rate in the QTL preliminary mapping results of rice grain y-aminobutyric acid content to genotype the 216 individual F2 populations and analyze the major QTL loci and loci effect.It was confirmed that the qGABA8 site on the chromosome 8 was the main QTL site,and the best genotype for screening for the exchange strain was HBA or BHA.2.Using the flanking marker approximation method,102 pairs of InDel markers were designed with the upstream and downstream markers RM342 and RM515 closely linked to the target gene,and 11 pairs of polymorphic markers were screened.The G56 and G58 markers were located at RM342.The initial mapping genetic map was further encrypted with RM515;the population consisting of Ningnong black carp/high glutinous rice-1 hybrid F2 and F2:3 pedigree 4350 single plants was used as the experimental material,and the recombinant individuals were screened by molecular markers to The obtained target segments were heterozygous and had high indica-1 genetic background.A total of 151 exchanged plants with genetic recombination in the localization interval were obtained,and the QTL qGABA8 secondary level of rice grain y-aminobutyric acid was localized in the marker RM342.Within a range of approximately 235 Kb with G56.3.F2:3 families 1020 strains derived from 151 exchange strains and 85 F2 exchange strains screened by secondary mapping,and F3:4 families 792 strains derived from 66 F2:3 exchanges were tested.A total of 1963 strains were used.RM342 and G56,which are closely linked to the target gene in the secondary location,were used as upstream and downstream markers.30 pairs of InDel markers were designed in the secondary location interval,including 1 pair of polymorphism markers(G121).The flanking marker approximation method was used to screen the exchange strains.Finally,53 exchange strains were screened in RM342 and G121,and the exchanged single plant phenotype was used for analysis.qGABA8 was finely located in the 183Kb range of RM342 and G121 markers.4.Combined with the qGABA8 fine mapping interval,it was found that there were 29 genes in the interval,and the 29 genes were separately analyzed by bioinformatics;there were 2 unknown functional genes and 27 genes encoding known domain proteins.Among the 27 known gene-encoded proteins,3 genes are associated with the retroviral GAG protein,indicating that there is a gene cluster encoding the viral receptor protein family in this region;21 genes are associated with the expressed protein,Of the 21 expressed proteins,6 genes,based on TMHMM and Signal PHMM,have a transmembrane domain or a signal peptide,suggesting that it may be a protein kinase or a transcription factor,and thus may play a role in rice life activities.There are also three genes with different roles.The LOC_Os08g32280.1 gene regulates up-and down-regulated protein spots in the whole proteome of rice roots;the LOC_Os08g32370.1 gene is a mucin-related surface protein;the nucleobase-ascorbate transporter in the LOC_Os08g32500.1 gene(NAT)is a highly hydrophobic protein with a similar number of genes found in the Arabidopsis and rice genomes. |
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