A Comparative Transcriptome and Metabolome Combined Analysis Reveals the Key Genes and Their Regulatory Model Responsible for Glucoraphasatin Accumulation in Radish Fleshy Taproots

Abstract

Radish (Raphanus sativus L.) is rich in specific glucosinolates (GSLs), which benefit human health and special flavor formation. Although the basic GSLs metabolic pathway in Brassicaceae plants is clear, the regulating mechanism for specific glucosinolates content in radish fleshy taproots is not well understood. In this study, we discovered that there was a significant difference in the GSLs profiles and the content of various GSLs components. Glucoraphasatin (GRH) is the most predominant GSL in radish taproots of different genotypes as assessed by HPLC analysis. Further, we compared the taproot transcriptomes of three radish genotypes with high and low GSLs content by employing RNA-seq. Totally, we identified forty-one differentially expressed genes related to GSLs metabolism. Among them, thirteen genes (RsBCAT4, RsIPMDH1, RsMAM1a, RsMAM1b, RsCYP79F1, RsGSTF9, RsGGP1, RsSUR1, RsUGT74C1, RsST5b, RsAPK1, RsGSL-OH, and RsMYB28) were significantly higher co-expressed in the high content genotypes than in low content genotype. Notably, correlation analysis indicated that the expression level of RsMYB28, as an R2R3 transcription factor directly regulating aliphatic glucosinolate biosynthesis, was positively correlated with the GRH content. Co-expression network showed that RsMYB28 probably positively regulated the expression of the above genes, particularly RsSUR1, and consequently the synthesis of GRH. Moreover, the molecular mechanism of the accumulation of this 4-carbon (4C) GSL in radish taproots was explored. This study provides new perspectives on the GSLs accumulation mechanism and genetic improvements in radish taproots.

Glucoraphanin Accumulation via Glucoraphanin Synthesis Promotion during Broccoli Germination

“…The changes in the expression of glucoraphanin synthesis-related genes were more comprehensively explored by completing RT-PCR analyses. The expression of CYP79F1 , CYP83A1 , and FMOGS-OX5 may enhance the conversion of precursor amino acids to activated compounds, which are subsequently used for secondary modifications [ 43 ]. The observed increase in the glucoraphanin accumulation ratio may have been caused by changes in the expression of CYP79F1 , CYP83A1 , and FMOGS-OX5 ( Figure 6 ).…”

Dynamic profiling of intact glucosinolates in radish by combining UHPLC-HRMS/MS and UHPLC-QqQ-MS/MS

“…(B) The biosynthetic pathway of methionine-derived GSLs. The biosynthetic pathway was referred to two previous investigations ( Kakizaki et al., 2017 ; Li et al., 2022 ). (C) An unknown biosynthetic pathway of aliphatic GSLs.…”

“…Besides, although 3-butenyl GSL (Gluconapin, GNP) and PRO were previously reported in Brassica plants, we were unable to discover these two typical aliphatic GSLs in our investigation. Interestingly, the absence of RsAOP2 and RsAOP3 dioxygenases, which are linked to GNP formation, has been found in two radish reference genomes ( Mitsui et al., 2015 ; Li et al., 2022 ). Fortunately, these variations reduced the contents of PRO and its animal-harming degradation product oxazolidine-2-thiones ( Petersen et al., 2018 ).…”

The Development and Application of Vegetable Genomics Increase the Efficiency of Exploring New Gene Resources for Vegetables

“…Radish is known for its accumulation of beneficial glucosinolates (GSLs). Li et al profiled the differential expression of GLS pathway genes between low and high GSL content radishes and proposed the central role of MYB28 in GLS biosynthesis [15]. Zhou et al compared five differentially colored eggplants (anthocyanin pigmented fruits, green fruits, and white fruits) and indicated the activation of early phenylpropanoid biosynthesis genes (SmPAL, SmC4H, and Sm4CL) was responsible for anthocyanin accumulation, while SmF3 ′ 5 ′ H was the key factor for the formation of a purple color.…”