Identification Of Glucosinolate Biosynthetic Gene And Mapping QTL For Glucosinolate In Brassica Rapa

Brassica rapa, including a variety of vegetable and oilseed crops, is an important species of the genus Brassica with good nutritional value, especially in Asia. With the gradual improvement of living standards, the quality traits of B. rapa were paid attention to. Glucosinolates, amino acids derived from thioglucosides, are specific to Cruciferae with important biologica and economic roles in plant defense and human nutrition. Although the near-cmplete knowledge of glucosinolate biosynthetic pathway was acquired in A. thaliana, little is known about the regulation of the biosynthesis and degradation in B. rapa. With the complete of B. rapa genome sequencing project, the understanding of glucosinolate biosynthsis, QTL for glucosinolate accumulation and candidate genes in B. rapa became possible.Profiles and content of glucosinolate was identified in B. rapa leaves, which provided basic information for nature variation and heredity of glucosinolate in B. rapa. Glucosinolate biosynthetic genes have been identified based on whole genome analysis of B. rapa and comparative genomic analyses between A. thaliana and B. rapa, and the glucosinolate biosynthetic pathway in B. rapa is clearly established. Four parents with different profile and leve of glucosinolate were selected, and three permanent population and related linkage maps were constructed together. QTL for glucosinolate accumulation was conducted then. Based on resequencing of 25 B. rapa, diversity of glucosinolate biosynthetic genes was ananlysed.The conclusions of this dissertation as follows:1. Glucosinolates were evaluated in 12 groups and 215 accessions of Brassica rapa. The eight glucosinolates detected by HPLC. The aliphatic glucosinolate 3-butenyl glucosinolate (NAP) was the most dominant glucosinolate with the highest ratio around 40%. We found huge difference of profiles and concentration between leafy B. rapa and turnip. A significant correlation was found between aliphatic glucosinolates in different seasons. Significant differences were observed for aliphatic glucosinolate among varieties, but no obvious variation was found between seasons. There was also a significant difference among indolic glucosinolates between seasons. The concentration of aromatic glucosinolate varied significantly among varieties of pak choi and turnip between seasons, but did not vary among varieties of Chinese cabbage.2. In order to elucidate the glucosinolate biosynthetic pathway in B. rapa, we conducted comparative genomic analyses of A. thaliana and B. rapa on a genome-wide level. We identified 102 putative genes in B. rapa as the orthologs of 52 glucosinolate genes in A. thaliana. All but one gene was successfully mapped on 10 chromosomes. A high co-linearity in the glucosinolate biosynthetic pathway between A. thaliana and B. rapa was also established. Most glucosinolate genes exist in more than one copy in B. rapa. The homologous glucosinolate genes between B. rapa and A. thaliana share 59 %– 91 % nucleotide sequence identity and 93% of the glcucosinolate genes exhibit synteny between B. rapa and A. thaliana. Moreover, the structure and arrangement of the B. rapa glucosinolate genes correspond with the known evolutionary divergence of B. rapa, and may help explain the profiles and accumulation of glucosinolate in B. rapa. 3. An integrated map of 1034.2 cM with 10 linkage groups, assigned to the international agreed nomenclature, is developed based on the BILs population with SSR, DArT, SRAP and InDel markers. Furthermore, another two maps were constructed based on two BC2DH populations with 194 and 132 Indel(Insertion-deletion) markers respectively, and these two maps covered 563.3 and 559.1 cM with 10 chromosomes of B.rapa respectively.4. Eight different glucosinolate compounds were detected in four parents and three populations in two different seasons respectively, and found to segregate quantitatively in the populations. QTL analysis identified six loci controlling aliphatic glucosinolate accumulation, two loci controlling total indolic glucosinolate concentration. Furthermore, we mapped the QTLs in the physical map of B. rapa by flanking InDel and SSR markers and identified BrMAM and BrAOP loci palyed an important role in controlling aliphatic glucosinolate accumulation B. rapa.5. Based on analysis resequencing data of 25 B. rapa, variation of glucosinolate biosynthetic genes was founded. About 63.1% glucosinolate biosynthetic genes existed SNP, while 26.5% included InDel in average material. Most of SNP and InDel distributed in intron, and few SNP and InDel lead to missense mutation or frameshift mutation.6. The correlation between variation of glucosinolate biosynthetic genes and glucosinolate content indicated 15 glucosinolate biosynthetic genes palyed a key role in accumulation of glucosinolate. Variation of lucosinolate biosynthetic gene in QTL loci in four parental materials suggested the SNP in splicing loci of BrMAM3 maybe the key variation lead to different profile and content in parental materials.