Low temperature is a major environmental factor, which limits rapeseed (Brassica napus L.) growth, development, and productivity. So far, the physiological and molecular mechanisms of rapeseed responses to cold stress are not fully understood. Here, we explored the transcriptome and metabolome profiles of two rapeseed genotypes with contrasting cold responses, i.e., XY15 (cold-sensitive) and GX74 (cold-tolerant). The global metabolome profiling detected 545 metabolites in siliques of both genotypes before (CK) and after cold-stress treatment (LW). The contents of several sugar metabolites were affected by cold stress with the most accumulated saccharides being 3-dehydro-L-threonic acid, D-xylonic acid, inositol, D-mannose, D-fructose, D-glucose, and L-glucose. A total of 1943 and 5239 differentially expressed genes were identified from the transcriptome sequencing in XY15CK_vs_XY15LW and GX74CK_vs_GX74LW, respectively. We observed that genes enriched in sugar metabolism and biosynthesis-related pathways, photosynthesis, reactive oxygen species scavenging, phytohormone, and MAPK signaling were highly expressed in GX74LW. In addition, several genes associated with cold-tolerance-related pathways, e.g., the CBF-COR pathway and MAPK signaling, were specifically expressed in GX74LW. Contrarily, genes in the above-mentioned pathways were mostly downregulated in XY15LW. Thus, our results indicate the involvement of these pathways in the differential cold-stress responses in XY15 and GX74.

Brassica napus L. is a vital oil crop and exhibits notable salt tolerance, making the enhancement of this trait crucial for cultivation in saline soils. Uncovering its underlying mechanism may further heighten the salt tolerance of B. napus. In this study, we conducted a genome-wide analysis of the Root Meristem Growth Factor (RGF) gene family in Brassica species and identified BnaRGF8 as a key regulator of salt tolerance. Under 200 mM NaCl treatment, all RGF genes were induced, with BnaRGF8 showing the greatest upregulation. This response was consistently observed across 10 genotypes, indicating a universal trend in B. napus. Functional characterization revealed that chemically synthesized BnaRGF8 alleviated salt-induced growth inhibition by restoring primary root elongation and lateral root formation. Additionally, BnaRGF8 preserved membrane integrity and maintained cell division under salt stress, establishing itself as a novel anti-salt peptide in B. napus.