Genetic Study Of Glucosinolate In Rapeseed By Associative Transcriptomics

Glucosinolates are a group of secondary metabolites containing nitrogen and sulfur,mainly found in the Brassicaceae.The chemical structure of glucosinolates is formed by a thioglucose moiety,a sulphonated oxime,and a variable side chain,derived from different amines.Regarding the derivation,the properties of individual glucosinolates were much different,rang from plant defense and auxin homeostasis to cancer prevention in humans.With the growth of living standard and the huge development of the breeding work,the improvement of glucosinolates in the seeds of B.napus has become one of the important breeding targets.In this study,Associative transcriptomics studies were conducted to dissect the genetic architecture of the the dynamic of GS content in seeds and silique walls and the compositions of seeds GS content.SNPs and GEMs,derived from m RNA-seq,were ultilized to conduct associative study with the traits for dissecting the genetic architecture of GS metabolism and transportation and finding the causative locus and candidate genes,which could be used in molecular assisted breeding to improve rapeseed quality.The main results are as followes:1.A subpanel,with relative consistent florescence,of panel AT1,was selected to analysis the dynamic of glucosinolate content in seeds and silique walls of B.napus.The total GS content of seeds and silique walls 15 days after pollination(DAP),25 DAP and mature seeds was detected.The results showed that the GS content in mature seeds and silique walls at 25 DAP was much more than other traits,and there was nearly no GS content in seeds at 15 DAP.Correlation analysis reflected that an obvious positive correlation was found between the GS content of mature seeds and silique walls at 25 DAP.2.13 individual glucosinolates were detected in panel AT1,including 7 aliphatic glucosinolates,4 indolyl glucosinolates and 2 aromatic glucosinolates.Aliphatic glucosinolates(ALI)took account for over 90% of total GS,while indolyl glucosinolates(INDOL)and aromatic glucosinolates(AROM)for about 7% and 2% separately.3.With SNPs,5 association peaks distributing across chromosome A2,A9,C2,C7 and C9 were found for mature seeds.Meanwhile,127,16 and 24 GEMs were significantly(-log10P>6.03)associated with GS content of mature seeds,seeds at 25 DAP,and silique walls at 25 DAP,respectively.As a result also unambiguously defined 5 association peaks in A2,A8,A9,C2,and C9 were detected.The association peaks in A9,C2 and C9 were common for both mature seeds and silique walls at 25 DAP.25 genes derived from the significant SNPs or GEMs were inferred and predicted to be involved in GS metabolic pathways.The proteins encoded by other genes derived from AT analysis,though not directly involved in GS metabolism,were classified as transcription factors,factors responding to stimulus or involved in cellular process,enzymes with catalytic activities and so on.4.With SNPs,4 well defined peaks on A02,A09,C02 and C09 were found associated with ALI in both two years.As contrast,there were not any peaks detected for INDOL,and 3 peaks found on A06,A09 and C08 in 2015 for AROM.For ELONG,4 distinct peaks were found,which coincided with the peaks detected by total aliphatic glucosinolates.For side-chain modification,only one well defined peak was found on A03 associated with ALI.1.In addition,the GEMs significantly associated with aliphatic GS formed four well defined peaks on A02,A09,C02 and C09,which were found to co-localize with the peaks detected by SNPs.To identify reliable significant association signals in our transcriptomic association study,only the genes in intervals of the significant peaks,or detecting by significant GEMs,or containing significant SNPs,were selected to mining the candidate gene response for the glucosinolate accumulation and composition in the rapeseed.In all,52 genes were directly implicated in the GS metabolism pathway,most of which were significantly associated with ALI.