Integrated transcriptomic and metabolomic analysis of prohexadione calcium-mediated alleviation of salt stress in oilseed rape (Brassica napus L.) seedlings

Salt stress severely limits the growth of oilseed rape (Brassica napus L.). Prohexadione calcium (Pro-Ca) has been reported to alleviate salt stress in oilseed rape. However, the underlying mechanisms of Pro-Ca-mediated salt stress alleviation in oilseed rape remains unclear. In this study, experimental materials were the kale-type oilseed rape varieties moderately salt-tolerant ‘Huayouza 158R’ and highly salt-tolerant ‘Huayouza 62’. 0, 100, and 150 mM NaCl were applied before sowing, and samples were collected after 21 days of cultivation to evaluate Pro-Ca priming on morphological, physiological, and molecular responses. Pro-Ca priming with 100 mM NaCl (Pro-Ca + S100) or 150 mM NaCl (Pro-Ca + S150) regulating morphogenesis, improving photosynthetic efficiency, and enhancing the antioxidant system compared with 100 mM NaCl (S100) and 150 mM NaCl (S150) alone. Transcriptomic analysis identified 381 and 832 differentially expressed genes (DEGs) in Huayouza 158R under Pro-Ca + S100-vs-S100 and Pro-Ca + S150-vs-S150, respectively, and 317 and 184 DEGs in Huayouza 62 under the same. Metabolomic analysis identified 312 and 487 differential metabolites (DIMs) in Huayouza 158R under Pro-Ca + S100-vs-S100 and Pro-Ca + S150-vs-S150, respectively, and 603 and 593 DIMs in Huayouza 62 under the same. Integrated transcriptomic and metabolomic analyses revealed that Pro-Ca priming up-regulated PLC4-related genes in the Huayouza 158R phosphatidylinositol signaling system pathway (ko04070) in S100. Under S150 treatment, Pro-Ca priming up-regulated YUCCA8 and YUCCA9 genes in the Huayouza 158R tryptophan metabolic pathway (ko00380), and down-regulated the abundance of indole-3-acetaldehyde. In Huayouza 62, Pro-Ca priming down-regulated lipoxygenase-related genes in the linoleic acid metabolic pathway (ko00591). In this pathway, lecithin was up-regulated while 9-KODE and 9,10,13-TriHOME were down-regulated in S100. In contrast, in S150, gamma-linolenic acid was up-regulated, while 9-KODE and 9,10,13-TriHOME were down-regulated. The results showed that Pro-Ca priming could alleviate the effects of salt stress in both oilseed rape varieties by regulating morphogenesis, improving photosynthetic efficiency, and enhancing the antioxidant system. However, the specific molecular mechanisms differ between the two varieties. This study provides a molecular basis for the alleviation of salt stress-induced damage by Pro-Ca-mediated in oilseed rape.