Transcriptomic and metabolomic analysis of roots of oiltea camellia

Nitrogen is an essential nutrient for plant growth, but its availability is limited in the soil of natural ecosystems. Usually, external nitrogen (N) supply is required for the cultured plants. It is important to discover the key genes for nitrogen utilization efficiency (NUE). To investigate the genes for NUE in oiltea camellia, we performed RNA-sequencing of oiltea root to reveal the genome-wide gene expression in response to three synthetic N forms, NH4+, NH4NO3, and NO3. The expression of a number of AMTs and NTRs was downregulated with all nitrogen forms and there were no AMTs or NTRs with significantly increased expression. Up- and downregulation of AQPs was seen in the NO3- and NH4NO3 treated plants, whereas only downregulation of AQPs was found following NH4+ treatment. Additionally, the metabolomic data showed that the accumulation of Glu and Gln was promoted by NH4+ and NH4NO3 treatment but not by NO3-. We suggest that the different expression profiles of genes involved in N transport and assimilation account for the different N uptake and concentrations of Glu and Gln in plants supplied with different N forms. This study will help improve the NUE and guide the agricultural production of oiltea camellia in the future.