Quantitative Trait Loci Identification and Candidate Genes Characterization for Indole-3-Carbinol Content in Seedlings of Brassica napus

Brassica napus is a member of the cruciferous family with rich glucosinolate (GSL) content, particularly glucobrassicin (3-indolylmethyl glucosinolate, I3M), that can be metabolized into indole-3-carbinol (I3C), a compound with promising anticancer properties. To unravel the genetic mechanism influencing I3C content in rapeseed seedlings, a comprehensive study was undertaken with a doubled haploid (DH) population. By quantitative trait loci (QTL) mapping, seven QTL that were located on A01, A07, and C04 were identified, with the most significant contribution to phenotypic variation observed on chromosome A07 (11.78%). The genes within the QTL confidence intervals (CIs) include transcription factors (TFs) and glycosyltransferases. After co-expression analysis, GSL-related regulatory network of TFs-targets was constructed and two TFs, BnaA07.ERF019 and BnaA07.NAC92, were identified as possible regulators in GSL biosynthesis. Three IGMT (glucosinolate methyltransferases) genes were found within the CIs that expressed higher in seedlings with more I3C, indicating their roles in I3C synthesis regulation. Molecular docking studies validated the binding capability of I3M to IGMTs, and those within the I3C QTL CIs have the strongest binding energy. These new discoveries offer critical insights into the genetic regulation of I3C content in rapeseed seedlings and establish a foundation for breeding high-I3C rapeseed varieties with potential health-promoting properties.