Genome-Wide Association Study of Phenylalanine Derived Glucosinolates in <i>Brassica rapa</i>
Guoxia Shang,
Huiyan Zhao,
Linhui Tong,
Nengwen Yin,
Ran Hu,
Haiyan Jiang,
Farah Kamal,
Zhi Zhao,
Liang Xu,
Kun Lu,
Jiana Li,
Cunmin Qu,
Dezhi Du
Affiliations
Guoxia Shang
Laboratory for Research and Utilization of Qinghai Tibet Plateau Germplasm Resources, Key Laboratory of Spring Rape Genetic Improvement, Academy of Agricultural and Forestry Sciences, Qinghai University, Xining 810016, China
Huiyan Zhao
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Linhui Tong
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Nengwen Yin
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Ran Hu
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Haiyan Jiang
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Farah Kamal
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Zhi Zhao
Laboratory for Research and Utilization of Qinghai Tibet Plateau Germplasm Resources, Key Laboratory of Spring Rape Genetic Improvement, Academy of Agricultural and Forestry Sciences, Qinghai University, Xining 810016, China
Liang Xu
Laboratory for Research and Utilization of Qinghai Tibet Plateau Germplasm Resources, Key Laboratory of Spring Rape Genetic Improvement, Academy of Agricultural and Forestry Sciences, Qinghai University, Xining 810016, China
Kun Lu
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Jiana Li
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Cunmin Qu
Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China
Dezhi Du
Laboratory for Research and Utilization of Qinghai Tibet Plateau Germplasm Resources, Key Laboratory of Spring Rape Genetic Improvement, Academy of Agricultural and Forestry Sciences, Qinghai University, Xining 810016, China
Glucosinolates (GSLs) are sulfur-containing bioactive compounds usually present in Brassicaceae plants and are usually responsible for a pungent flavor and reduction of the nutritional values of seeds. Therefore, breeding rapeseed varieties with low GSL levels is an important breeding objective. Most GSLs in Brassica rapa are derived from methionine or tryptophan, but two are derived from phenylalanine, one directly (benzylGSL) and one after a round of chain elongation (phenethylGSL). In the present study, two phenylalanine (Phe)-derived GSLs (benzylGSL and phenethylGSL) were identified and quantified in seeds by liquid chromatography and mass spectrometry (LC-MS) analysis. Levels of benzylGSL were low but differed among investigated low and high GSL genotypes. Levels of phenethylGSL (also known as 2-phenylethylGSL) were high but did not differ among GSL genotypes. Subsequently, a genome-wide association study (GWAS) was conducted using 159 B. rapa accessions to demarcate candidate regions underlying 43 and 59 QTNs associated with benzylGSL and phenethylGSL that were distributed on 10 chromosomes and 9 scaffolds, explaining 0.56% to 70.86% of phenotypic variations, respectively. Furthermore, we find that 15 and 18 known or novel candidate genes were identified for the biosynthesis of benzylGSL and phenethylGSL, including known regulators of GSL biosynthesis, such as BrMYB34, BrMYB51, BrMYB28, BrMYB29 and BrMYB122, and novel regulators or structural genes, such as BrMYB44/BrMYB77 and BrMYB60 for benzylGSL and BrCYP79B2 for phenethylGSL. Finally, we investigate the expression profiles of the biosynthetic genes for two Phe-derived GSLs by transcriptomic analysis. Our findings provide new insight into the complex machinery of Phe-derived GSLs in seeds of B. rapa and help to improve the quality of Brassicaceae plant breeding.
