Abstract
Vegetable oil is an essential constituent of the human diet and renewable raw material for industrial applications. Enhancing oil production by increasing seed oil content in oil crops is the most viable, environmentally friendly, and sustainable approach to meet the continuous demand for the supply of vegetable oil globally. An in-depth understanding of the gene networks involved in oil biosynthesis during seed development is a prerequisite for breeding high-oil-content varieties. Rapeseed (Brassica napus) is one of the most important oil crops cultivated on multiple continents, contributing more than 15% of the world’s edible oil supply. To understand the phasic nature of oil biosynthesis and the dynamic regulation of key pathways for effective oil accumulation in B. napus, comparative transcriptomic profiling was performed with developing seeds and silique wall (SW) tissues of two contrasting inbred lines with ~13% difference in seed oil content. Differentially expressed genes (DEGs) between high- and low-oil content lines were identified across six key developmental stages, and gene enrichment analysis revealed that genes related to photosynthesis, metabolism, carbohydrates, lipids, phytohormones, transporters, and triacylglycerol and fatty acid synthesis tended to be upregulated in the high-oil-content line. Differentially regulated DEG patterns were revealed for the control of metabolite and photosynthate production in SW and oil biosynthesis and accumulation in seeds. Quantitative assays of carbohydrates and hormones during seed development together with gene expression profiling of relevant pathways revealed their fundamental effects on effective oil accumulation. Our results thus provide insights into the molecular basis of high seed oil content (SOC) and a new direction for developing high-SOC rapeseed and other oil crops.
Highlights
Vegetable oil is an essential component of food and crucial for human health, and a renewable resource for biodiesel and other industrial raw materials [1,2]
Differentially expressed genes (DEGs) in pathways closely related to lipid metabolism were upregulated, such as fatty acid biosynthesis, sphingolipid metabolism, glycerolipid metabolism, lipid protein biosynthesis, and lipid metabolism, while DEGs in pathways involved in protein and carbohydrate accumulation were downregulated, such as starch and sucrose metabolism, amino acid metabolism, and synthesis
Understanding the dynamic regulation of seed oil content (SOC) during seed development is vital for precise breeding and genetic engineering of high oil variants in the crop, as even a slight percentage improvement in SOC in the field will lead to significant economic value [29]
Summary
Vegetable oil is an essential component of food and crucial for human health, and a renewable resource for biodiesel and other industrial raw materials [1,2]. Contrasting observations of temporal changes in the expression pattern of oil biosynthesis genes during seed development have been reported in previous studies on B. napus. Earlier studies showed that lipid biosynthesis pathways in Brassica seeds are similar to Arabidopsis, there are very few references available on transcriptomic regulation of oil accumulation in seeds and silique wall across the major seed development stages in the crop, especially in field conditions. Significantly higher contents of glucose, sucrose, and starch were observed in the HOCL as compared to LOCL during the key phase of oil biosynthesis from 23 to 44 DAP in seed and SW tissues. The results support the hypothesis that carbon flux during the key oil biosynthesis phase is the foundation for effective oil accumulation
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