Integration of the metabolome and transcriptome reveals the resistance mechanism to low nitrogen in wild soybean seedling roots

Wild soybean is the progenitor of cultivated soybean that has excellent low-nitrogen (N) tolerance. This study revealed the mechanism of resistance to low N in wild soybean seedling roots by analyzing the differences in the physiology, metabolome and transcriptome. Under low-N stress, low-N-tolerant wild soybean seedling roots underwent less growth inhibition, producing longer roots that had a higher carbon (C)/N ratio and C, NO3-, Fe2+, Zn2+, Ca2+, K+ and B3+ contents compared with common wild soybean. The comparison of the metabolomes and transcriptomes of two genotypes of wild soybean revealed that low-N-tolerant wild soybean reduced its energy consumption by decreasing the synthesis of energy-consuming amino acids. In addition, it enhanced the synthesis of proline and secondary metabolites to resist low-N stress. Enhancing the metabolism of shikimic acid was a unique mechanism involved in low-N tolerance of the low-N-tolerant wild soybean. Moreover, some genes involved in flavonoid synthesis were identified. This study could provide a basis for the investigation and application of wild resources in soybean breeding.