Enhanced lignin and cellulose metabolism promote cell wall synthesis and growth of wild soybean HRA under alkali stress

Abstract Background and Aims Soil salinization adversely threatens plant survival and food production globally. The mobilization of storage reserves in cotyledons and establishment of the hypocotyl/root axis (HRA) structure and function are crucial to the growth of dicotyledonous plants during the post-germination growth period. Here we report the adaptive mechanisms of wild and cultivated soybeans in response to alkali stress in soil during the post-germination growth period. Methods Differences in physiological parameters, microstructure, and the types, amounts and metabolic pathways of small-molecule metabolites and gene expression were compared and multi-omics integration analysis was performed between wild and cultivated soybean under sufficient and artificially simulated alkali stress during the post-germination growth period in this study. Key Results Structural analysis showed that the cell wall thickness of wild soybean under alkali stress increased, whereas cultivated soybeans were severely damaged. A comprehensive analysis of small-molecule metabolites and gene expression revealed that protein breakdown in wild soybean cotyledons under alkali stress was enhanced, and transport of amino acids and sucrose increased. Additionally, lignin and cellulose syntheses in wild soybean HRA under alkali stress were enhanced. Conclusions Overall, protein decomposition and transport of amino acids and sucrose increased in wild soybean cotyledons under alkali stress, which in turn promoted HRA growth. Similarly, alkali stress enhanced lignin and cellulose synthesis in the wild soybean HRA, which subsequently enhanced cell wall synthesis, thereby maintaining the stability and functionality of the HRA under alkali stress. This study presents important practical implications for the utilization of wild plant resources and sustainable development of agriculture.