Abstract
Nicotine, a major alkaloid in tobacco plants, acts as a defensive compound against insects. Nicotine is produced in the tobacco roots and transported to the leaves for storage. Nicotine level is controlled by two unlink loci, Nic1 and Nic2. We analyzed the difference in the expression pattern between wild-type root and low alkaloid mutant (nic1nic2) root by using fluorescence differential display technique. We found several genes were reduced in expression in the mutant root. Among them, two genes (NtMATE1, NtMATE2) encode similar proteins, which contain 12 putative transmembrane segments, with homology to multidrug and toxic compound extrusion (MATE) family transporters. These proteins are very similar to TRANSPARENTS TESTA 12, which may control the vacuolar sequestration of proanthocyanidins in Arabidopsis thaliana. Expression of these genes was tightly controlled by NIC regulatory genes and observed specifically in the wild type root. These results suggest that these transporter-like proteins participate in nicotine transport.
