Comparative analysis of carbon and nitrogen metabolism, antioxidant indexes, polysaccharides and lobetyolin changes...

Codonopsis pilosula is a traditional Chinese herbal medicinal plant and contains various bioactive components, such as C. pilosula polysaccharides (CPPs) and lobetyolin (Lob). Hydrogen peroxide (H₂O₂) and nitric oxide (NO) are gaseous molecule and have been well known for their ability to relieve some adverse influences on plant from abiotic stress. Endophytic fungus is non-pathogenic plant-associated fungus that could play a significant role in improving plant tolerance by signal molecule. In this work, we determined how inoculation of Trichoderma strain RHTA01 with C. pilosula changed the plant's growth, metabolite accumulation, and related enzyme activity. Results demonstrated that application of Trichoderma strain RHTA01 significantly improved the growth of C. pilosula. Moreover, it noticeably decreased antioxidant enzyme superoxide dismutase (SOD) and catalase (CAT) activity in C. pilosula leaves, reduced the content of H₂O₂ and malondialdehyde (MDA), and weakened the peroxidation of cell membrane lipids, which reduced the damage of abiotic stress to C. pilosula. Research has shown that it had obvious effects on levels of nitrogen and carbon metabolic enzymes. For example, sucrose synthase (SS) and acid invertase (AI) levels in C. pilosula roots were nearly 1.43 and 1.7 times higher, respectively, than those in the control (CK) group. In addition, it was notable that the production of CPPs and Lob, the most significant secondary metabolites in C. pilosula, were influenced by Trichoderma strain RHTA01. The obtained results indicate that inoculating C. pilosula with Trichoderma stimulates the carbon and nitrogen metabolism of the plant, and helps to increase the content of CPPs and Lob in the root of the plant.