Genome-Wide Characterization of the Brassica juncea NDPK Gene Family and Functional Analysis in Root Development Under Drought Stress

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.