Role of Endophytic Bacteria in the Remobilization of Leaf Nitrogen Mediated by CsEGGT in Tea Plants (Camellia sinensis L.)

As an important economic plant, tea (Camellia sinensis) has a good economic value and significant health effects. Theanine is an important nitrogen reservoir, and its synthesis and degradation are considered important for nitrogen storage and remobilization in tea plants. Our previous research indicated that the endophyte CsE7 participates in the synthesis of theanine in tea plants. Here, the tracking test confirmed that CsE7 tended to be exposed to mild light and preferentially colonized mature tea leaves. CsE7 also participated in glutamine, theanine, and glutamic acid circulatory metabolism (Gln-Thea-Glu) and contributed to nitrogen remobilization, mediated by the gamma-glutamyl-transpeptidase (CsEGGT) with hydrolase preference. The reisolation and inoculation of endophytes further verified their role in accelerating the remobilization of nitrogen, especially in the reuse of theanine and glutamine. This is the first report about the photoregulated endophytic colonization and the positive effect of endophytes on tea plants mediated and characterized by promoting leaf nitrogen remobilization.

Automated summary

As an important economic plant, tea (Camellia sinensis) has good economic value and significant health effects. The synthesis and degradation of theanine by the endophyte CsE7 play a crucial role in nitrogen storage and remobilization in tea plants. CsE7 tends to colonize mature tea leaves exposed to mild light, and it participates in the circulatory metabolism of glutamine, theanine, and glutamic acid (Gln-Thea-Glu), contributing to nitrogen remobilization. The positive effect of endophytes on tea plants in promoting leaf nitrogen remobilization, particularly through the reuse of theanine and glutamine, is reported for the first time.