One gene, two gains: New discovery increases sterols and oils in rapeseed
image: Construction and analysis of transcriptional regulatory networks involving TS-related TFs and target genes and analysis of cis-acting elements in the promoters of SQS1 homologous genes.
Credit: Horticulture Research
Sterols are beneficial plant metabolites with proven human health effects. In rapeseed (Brassica napus), enhancing sterol content could add significant nutritional value to edible oils. This study integrated quantitative trait locus (QTL) mapping with time-series transcriptomics to explore the genetic architecture of sterol metabolism. Researchers identified 24 QTLs and 157 metabolic QTLs (mQTLs) related to sterol traits and discovered a key regulatory gene, BnSQS1.C03. Functional validation showed that overexpressing BnSQS1.C03 in Arabidopsis increased total sterol content by 3.8%. This integrative approach provides valuable genetic resources for breeding high-sterol rapeseed varieties and offers new insights into sterol-lipid metabolic crosstalk.
Phytosterols not only support plant development but also offer health benefits such as cholesterol-lowering, anti-inflammatory, and anticancer properties. Rapeseed oil, rich in phytosterols like β-sitosterol and brassicasterol, is a valuable dietary source of these compounds. However, efforts to genetically enhance sterol levels in rapeseed have been limited by gaps in understanding the metabolic and genetic regulation of sterol biosynthesis. While prior studies have mapped a few sterol-related quantitative trait locus (QTL), comprehensive genetic dissection at the population level has remained elusive.
Researchers from Huazhong University of Science and Technology and collaborating institutions published a study (DOI: 10.1093/hr/uhae196) on July 24, 2024, in Horticulture Research, revealing a comprehensive genetic map of sterol biosynthesis in rapeseed. The team integrated QTL mapping with transcriptomics to uncover 24 sterol-related QTLs and identified BnSQS1.C03 as a pivotal gene influencing both sterol and oil content. Functional assays in Arabidopsis confirmed its role in enhancing squalene synthesis and total sterol accumulation, providing a promising genetic target for oil crop improvement.
Using a double haploid (DH) population of B. napus, the researchers quantified total sterol (TS) and 21 individual sterol components over multiple years. They discovered 24 QTLs and 157 mQTLs that regulate various sterol traits, with major hotspots on chromosomes A08 and C03. Co-localization analysis indicated shared regulatory regions between TS, single sterols, and seed oil content (SOC). Transcriptomic profiling across seed developmental stages revealed 7548 differentially expressed genes (DEGs), with many involved in sterol and lipid metabolism.
By integrating QTL and transcriptomic data, the team constructed a transcriptional regulatory network and highlighted BnSQS1.C03 as a candidate gene. In vitro enzyme assays confirmed its function as a squalene synthase, catalyzing the formation of squalene from farnesyl pyrophosphate. Transgenic Arabidopsis lines overexpressing BnSQS1.C03 showed a 3.8% increase in TS and modest gains in oil content. Conversely, TS and SOC dropped sharply in knockout mutants. These findings establish BnSQS1.C03 as a central regulator of sterol biosynthesis and reveal its influence on lipid accumulation. The study also uncovered regulatory motifs in its promoter responsive to plant hormones such as ABA, suggesting complex cross-talk between sterol and hormonal signaling.
“This study marks a significant step toward understanding and manipulating sterol biosynthesis in rapeseed,” said Dr. Maoteng Li, corresponding author of the study. “By combining QTL mapping with transcriptomic data, we not only pinpointed key genetic loci but also validated the functional role of BnSQS1.C03 in regulating sterol content. The discovery of its dual effect on both sterol and oil content opens new doors for improving nutritional quality and economic value of rapeseed oil through molecular breeding.”
The identification and validation of BnSQS1.C03 provide a new genetic target for enhancing phytosterol content in rapeseed, a critical step toward breeding functional oil crops with added health benefits. Since sterols contribute to membrane integrity and serve as precursors for hormones like brassinosteroids, this gene may also support stress resilience in crops. The gene's additional influence on oil content suggests that it could help overcome the typical trade-off between oil yield and nutritional quality. These findings offer a promising molecular tool for breeders aiming to develop rapeseed varieties that combine high yield with improved functional traits, supporting both agricultural sustainability and human health.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae196
Funding information
This study was supported by the National Key Research and Development Program of China (2023YFD1201401) and the National Natural Science Foundation of China (32272067 and 32072098).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.