Heat Stress and Microbial Stress Induced Defensive Phenol Accumulation in Medicinal Plant Sparganium stoloniferum

An approach based on the heat stress and microbial stress model of the medicinal plant Sparganium stoloniferum was proposed to elucidate the regulation and mechanism of bioactive phenol accumulation. This method integrates LC-MS/MS analysis, 16S rRNA sequencing, RT-qPCR, and molecular assays to investigate the regulation of phenolic metabolite biosynthesis in S. stoloniferum rhizome (SL) under stress. Previous research has shown that the metabolites and genes involved in phenol biosynthesis correlate to the upregulation of genes involved in plant-pathogen interactions. High-temperature and the presence of Pseudomonas bacteria were observed alongside SL growth. Under conditions of heat stress or Pseudomonas bacteria stress, both the metabolites and genes involved in phenol biosynthesis were upregulated. The regulation of phenol content and phenol biosynthesis gene expression suggests that phenol-based chemical defense of SL is stimulated under stress. Furthermore, the rapid accumulation of phenolic substances relied on the consumption of amino acids. Three defensive proteins, namely Ss4CL, SsC4H, and SsF3'5'H, were identified and verified to elucidate phenol biosynthesis in SL. Overall, this study enhances our understanding of the phenol-based chemical defense of SL, indicating that bioactive phenol substances result from SL's responses to the environment and providing new insights for growing the high-phenol-content medicinal herb SL.