A Single Latent Plant Growth-Promoting Endophyte BH46 Enhances Houttuynia cordata Thunb. Yield and Quality

Plant growth-promoting endophytes (PGPE) can effectively regulate plant growth and metabolism. The regulation is modulated by metabolic signals, and the resulting metabolites can have considerable effects on the plant yield and quality. Here, tissue culture Houttuynia cordata Thunb., was inoculated with Rhizobium sp. (BH46) to determine the effect of BH46 on H. cordata growth and metabolism, and elucidate associated regulatory mechanisms. The results revealed that BH46 metabolized indole-3-acetic acid and induced 1-aminocyclopropane-1-carboxylate deaminase to decrease ethylene metabolism. Host peroxidase synthesis MPK3/MPK6 genes were significantly downregulated, whereas eight genes associated with auxins, cytokinins, abscisic acid, jasmonic acid, and antioxidant enzymes were significantly upregulated. Eight genes associated with flavonoid biosynthesis were significantly upregulated, with the CPY75B1 gene regulating the production of rutin and quercitrin and the HCT gene directly regulating the production of chlorogenic acid. Therefore, BH46 influences metabolic signals in H. cordata to modulate its growth and metabolism, in turn, enhancing yield and quality of H. cordata.