Combined dynamic transcriptome and flavonoid metabolome reveal the role of Mo nanoparticles in the nodulation process...

Symbiotic nitrogen fixation can reduce the impact of agriculture on the environment by reducing fertilizer input. The rapid development of nanomaterials in agriculture provides a new prospect for us to improve the biological nitrogen fixation ability of leguminous crops. Molybdenum is an important component of nitrogenase, and the potential application of MoO₃NPs in agriculture is largely unexplored. In this study, on the basis of verifying that MoO₃NPs can improve the nitrogen fixation ability of soybean, the effects of MoO₃NPs on the symbiotic nitrogen fixation process of soybean were investigated by using dynamic transcriptome and targeted metabolome techniques. Here we showed that compared with conventional molybdenum fertilizer, minute concentrations of MoO₃NPs (0.01-0.1 mg kg^-1) could promote soybean growth and nitrogen fixation efficiency. The nodules number, fresh nodule weight and nitrogenase activity of 0.1 mg kg^-1 were increased by 17 %, 14 % and 27 %, and plant nitrogen accumulation increased by 17 %. Compared with conventional molybdenum fertilizer, MoO₃NPs had a greater effect on apigenin, kaempferol and other flavonoid, and the expression of nodulation related genes such as ENOD93, F3'H. Based on WGCNA analysis, we identified a core gene GmCHS9 that was positively responsive to molybdenum and was highly expressed during MoO₃NPs induced nodulation. MoO₃NPs could improve the nitrogen fixation ability of soybean by promoting the secretion of flavonoids and the expression of key genes. This study provided a new perspective for the nano-strengthening strategy of nodules development and flavonoid biosynthesis by molybdenum.