Molecular cloning and expression analysis of ammonium transporters in tea plants (Camellia sinensis (L.) O. Kuntze) under different nitrogen treatments

Ammonium is a major inorganic nitrogen source for tea plant growth and is mainly taken up and transported by ammonium transporters (AMTs). Here, we analyzed the NH4+ uptake kinetics of three tea cultivars, Longjing43 (LJ43), Zhongcha108 (ZC108) and Zhongcha302 (ZC302). The results revealed that ZC302 had a higher NH4+ uptake efficiency than the other two cultivars. The full CDS sequences of three Camellia sinensis ammonium transporter (CsAMT) genes, i.e., CsAMT1.1, CsAMT1.2 and CsAMT3.1, were cloned. Analysis of tissue-specific expression showed that CsAMT1.2 followed a root-specific expression pattern, while transcripts of CsAMT1.1 and CsAMT3.1 were mainly accumulated in leaves. The temporal course experiment on gene expression levels showed CsAMT1.1 and CsAMT3.1 followed a reciprocal expression pattern in leaves as CsAMT1.1 was up-regulated by a short time (2 h, 6 h) nitrogen (N) supply both in the leaves and buds of LJ43 and ZC108; and the expression of CsAMT3.1 in leaves was increased by a long time (72 h) N supply, particularly in ZC302. Therefore, we inferred that CsAMT1.1 and CsAMT3.1 might play important roles in photorespiratory ammonium metabolism. The expression of CsAMT1.2 was extremely high in roots and can be greatly induced by N over a short period of time, especially in ZC302; thus, we concluded CsAMT1.2 might play an important role in ammonium uptake from soils in tea plant roots.