Adaptive physiological traits and flavonoid metabolism of Nekemias grossedentata on coal gangue stress

Coal gangue pollution caused by coal mining is a serious ecological problem, phytoremediation is considered to be the best treatment model. Nekemias grossedentata(NG), the king of flavonoids, is found in some coal mining areas. However, its adaptation mechanism to gangue stress remains unclear. Exploring the physiological response and metabolic changes of NG in gangue matrices aims to provide important insights into ecological restoration of mines. Here, an integrative analysis of physiological, metabolome and transcriptome of NG under normal and stress conditions was performed. Under gangue stress, the activities of SOD, POD, GST, ASA and CAT in NG increased by 1.76, 1.67, 1.47, 1.19 and 1.19 times, respectively. Meanwhile, the contents of soluble sugars, total phenols, total flavonoids, and proline enhanced by 1.32, 1.23, 1.20 and 1.16 times. Additionally, metabolomics analysis showed that 37 flavonoids were upregulated with varying degrees, among which nobiletin, kaempferol and (-)-catechin showed significant upregulation, with 12.65, 2.32 and 2.19 times. Compared with the control group, the genes encoded by FLS, F3'H, F3'5'H and C3'H were up-regulated by 1.69, 1.34, 1.31, 1.15 folds, indicating that they play an important role in regulating the main biosynthetic pathways of flavonoids. And the genes CAT and VCT4 upregulated 1.45 and 1.41 folds, indicating that they need to play an important role in regulating plant antioxidant enzyme activity. These findings uncover the dynamic changes and molecular mechanisms of flavonoids and other stress factors under coal gangue stress, presenting new opportunities for gangue ecological restoration and nobiletin metabolic accumulation.