Identification of environment-insensitive genes for oil content by combination of transcriptome and genome-wide association analysis in rapeseed

The primary objective of rapeseed breeding is to enhance oil content, which is predominantly influenced by environmental factors. However, the molecular mechanisms underlying the impact of these environmental factors on oil accumulation remain inadequately elucidated. In this study, we used transcriptome data from two higher (HOC) and two lower oil content (LOC) inbred lines at 35 days after pollination (DAP) to investigate genes exhibiting stable expression across three different environments. Meanwhile, a genome-wide association study (GWAS) was utilized to detect candidate genes exhibiting significant associations with seed oil content across three distinct environments.

The study found a total of 405 stable differentially expressed genes (DEGs), including 25 involved in lipid/fatty acid metabolism and 14 classified as transcription factors. Among these genes, BnBZIP10-A09, BnMYB61-A06, BnAPA1-A08, BnPAS2-A10, BnLCAT3-C05 and BnKASIII-C09 were also found to exhibit significant associations with oil content across multiple different environments based on GWAS of 50 re-sequenced semi-winter rapeseed inbred lines and previously reported intervals. Otherwise, we revealed the presence of additive effects among BnBZIP10-A09, BnKASIII-C09, BnPAS2-A10 and BnAPA1-A08, resulting in a significant increase in seed oil content. Meanwhile, the majority of these stable DEGs are interconnected either directly or indirectly through co-expression network analysis, thereby giving rise to an elaborate molecular network implicated in the potential regulation of seed oil accumulation and stability.

The combination of transcription and GWAS revealed that natural variation in six environment-insensitive gene regions exhibited significant correlations with seed oil content phenotypes. These results provide important molecular marker information for us to further improve oil content accumulation and stability in rapeseed.