Abstract
Genes homologous to mammalian Na+/bile acid transporter (NBT) exist in Arabidopsis thaliana and rice genome sequences. Their functions are still unknown, but a gene encoding an NBT homologue is expressed higher in C4 species than in C3 species of Flaveria (Yamaguchi et al. 2002, Plant Cell Physiol. Suppl 43 3aB09). It suggests that the homologue may be related to C4 pathway.
We have isolated a full length cDNA of a putative NBT homologue (McNBT) from the leaf tissue of Mesembryanthemum crystallinum, a facultative Crassulacean acid metabolism (CAM) plant. McNBT encodes a protein which shows 78% homology to the Arabidopsis protein. Low level expression of this gene is detected in the leaf and root tissues of C3 mode of M. crystallinum by using semi-quantitative RT-PCR technique. During CAM induction by addition of 0.35 M NaCl to the rooting medium, mRNA level of the gene is increased only in the leaf tissue.
