Soil salinity is one of the most significant abiotic stresses affecting crop yield around the world. To explore the molecular mechanism of salt tolerance in rapeseed (Brassica napus L.), the transcriptome analysis and metabolomics analysis were used to dissect the differentially expressed genes and metabolites in two rapeseed varieties with significant differences in salt tolerance; one is an elite rapeseed cultivar, Huayouza 62. A total of 103 key differentially expressed metabolites (DEMs) and 53 key differentials expressed genes (DEGs) that might be related to salt stress were identified through metabolomics and transcriptomics analysis. GO and KEGG analysis revealed that the DEGs were mainly involved in ion transport, reactive oxygen scavenging, osmotic regulation substance synthesis, and macromolecular protein synthesis. The DEMs were involved in TCA cycle, proline metabolism, inositol metabolism, carbohydrate metabolic processes, and oxidation-reduction processes. In addition, overexpression of BnLTP3, which was one of the key DEGs, could increase tolerance to salt stress in Arabidopsis plants. This study reveals that the regulation mechanism of salt tolerance in rapeseed at the transcriptome and metabolism level and provides abundant data for further in-depth identification of essential salt tolerance genes.

Cultivating salt-alkali-tolerant crops is crucial for ensuring food security and utilizing marginal lands. This study aimed to evaluate and compare the physiological and nutritional responses of rapeseed and pea seedlings to saline and alkaline stresses to assess their potential for intercropping in affected areas. Using saline-alkali-tolerant rapeseed 'Huayouza 158R' and dwarf pea 'Zhongwan 11' as materials, the effects of different concentrations of salt (NaCl) and alkali (Na₂CO₃) stress on the growth and main nutritional quality of rapeseed and pea seedlings were studied. The results showed that both salt and alkali stress could inhibit the growth of rapeseed and pea seedlings, and the content of main nutrients, mainly reflected in the inhibition of the growth of the aerial parts and roots, the reduction of biomass accumulation, and the reduction of the content of vitamin C, soluble sugar, and soluble protein in leaves. By comparing the salt and alkali tolerance of rapeseed and pea, it was found that rapeseed has strong salt tolerance and relatively weak alkali tolerance, while pea has strong alkali tolerance and relatively weak salt tolerance. The results of this study provide theoretical support for the possibility of promoting the intercropping and mixed sowing of rapeseed and pea in saline-alkali land.

Nucleoside diphosphate kinases (NDPKs) constitute a multifunctional enzyme family that is widely distributed in prokaryotes and eukaryotes and plays important roles in energy metabolism, stress perception, signal transduction, and reactive oxygen species homeostasis. However, this gene family has not been systematically characterized in Brassica juncea. Here, we performed a genome-wide identification and comprehensive analysis of the BjNDPK gene family by integrating bioinformatic analyses with expression and physiological assays. Eighteen non-redundant BjNDPK genes were identified and classified into five phylogenetic groups with distinct structural features. Cis-acting element analysis showed that the promoters of several members contain drought-responsive elements. Collinearity analysis indicated complex subgenomic rearrangement and selective retention during the allotetraploid evolution of B. juncea . Expression profiling showed that many BjNDPK genes differed among tissues and responded to PEG-induced osmotic stress and salt stress. Reference-gene stability analysis identified qBjActin as the most stable reference gene under the tested conditions. Physiological assays showed that PEG treatment increased the content of H ₂ O ₂ in B. juncea leaves, whereas an Arabidopsis thaliana atndpk2 (corresponding to BjNDPK7 in B. juncea ) mutant maintained greater root elongation than the wild type under mannitol treatment. These findings describe the structural, evolutionary, and expression characteristics of the BjNDPK family and provide candidate genes for future functional studies of abiotic-stress responses in polyploid B. juncea .

Nucleoside diphosphate kinase (NDPK) is a multifunctional enzyme family widely distributed in both prokaryotic and eukaryotic organisms, playing crucial roles in energy metabolism, stress perception, signal transduction, and reactive oxygen species (ROS) regulation. However, this gene family has not been systematically identified and functionally characterized in Brassica juncea . This study conducted a genome-wide identification and comprehensive analysis of the BjNDPK gene family in Brassica juncea , integrating bioinformatics and experimental validation based on the Brassica juncea genome data. A total of 18 BjNDPK family members were identified. Their encoded proteins retain high sequence and structural conservation within the NDPK family while exhibiting structural features adapted to diverse functions. Analysis of cis-acting elements revealed that multiple members possess promoters rich in drought-response-related elements. Colinearity analysis indicated that BjNDPK genes underwent complex subgenomic rearrangements and selective retention during the formation of Brassica juncea heterotetraploidy. Expression profiling showed that most BjNDPK genes responded significantly during different tissue development stages and under drought stress, with some members highly expressed in seed-related tissues. Furthermore, internal gene stability assessment confirmed qBjActin exhibits outstanding expression stability in this study system. Physiological experiments further demonstrated that drought stress induces oxidative stress in Brassica juncea , while the AtNDPK2 mutant in Arabidopsis thaliana exhibits enhanced root growth capacity under osmotic stress. This study systematically analyzed the structure, evolution, and expression characteristics of the BjNDPK gene family in rapeseed, laying a theoretical foundation for investigating its functional mechanisms in abiotic stress responses and providing important candidate gene resources.