UNE Gene Family Analysis and Overexpression of UNE12 Enhances Salt Resistance in Brassica napus

Abstract Salt stress inhibits the growth, development, yield, and quality formation of the oilseed crop (rapeseed). This study identifies salt tolerance determinants within the UNE gene family of Brassica napus through integrated genomic and functional analyses. Genome-wide characterization revealed 21 BnUNE genes exhibiting structural diversification and parallel evolution with orthologs in Brassica rapa and Brassica oleracea, while core functional domains remained conserved. Phylogenetic analysis classified BnUNEs into 6 subclades with distinct motif architectures, intron/exon patterns, and predicted subcellular localization. Notably, subclade I members showed unique intron insertions and peroxisomal targeting, suggesting specialized roles in reactive oxygen species (ROS) metabolism and detoxification. Functional validation demonstrated that under 300 mM NaCl stress, transgenic lines BnUNE12-OE exhibited significantly enhanced salt tolerance compared to wild-type (WT) plants. The results that increased root length and fresh weight (37.2% and 29.8%), reduced the malondialdehyde (MDA) content (31.5%), elevated proline accumulation (2.3-fold), upregulated antioxidant genes (SOD1, CAT2). The study demonstrates that BnUNE12 significantly enhances salt stress tolerance in B. napus by synergistically regulating osmotic balance (promoting proline accumulation) and alleviating oxidative stress (enhancing ROS detoxification capacity). This work elucidated the adaptive evolution of the UNE gene family within the Brassica genus, and established BnUNE12 as a key molecular target for breeding salt tolerant rapeseed cultivars, providing a valuable genetic resource for molecular breeding of stress-resistant crops.