Characterization of a novel plant gene that confers salt tolerance to Escherichia coli

To identily genes with crucial role in plant adaptationi tolerance to osmotic stress we have recently isolated, through a functional approach, different potato cONA clones able to conler NaCI tolerance to E coli cells. One of these, clone N2.1, has an ORF coding for a protein of 433 aminoacids with i?nteresti?nq features, including three putative intraspanning membrane domains along with a consensus motif for ATP/GTP binding. The gene is con- stitutively expressed in potato root tissues and its expression seems not to be regulated by NaCI (100mM). Homology search in the Arabidopsis genome database identified a single gene sequence which share 72% identity with the potato N2.1 clone, presently classified as unknown protein. As detected by RT-PCR, in 15 day- old Arabidopsis seedlings the gene is expressed at very low level, but it is rapidly and highly activated upon salt stress (160mM NaCI). Beside sodium, the gene is also highly induced by different ions such as K+ (125 mM KCI), Li+ (25 mM LiCI), and Cs+ (18 mM CsCI). Arabidopsis transgenic plants with sense and antisense constructs have been obtained and two different T-DNA insertion lines of the Salk collection have been identilied. Their phenotypic and molecular characterization are currently under way to deline the functional role of N2. 1 gene in the pathway of the plant celle response to salt and osmotic stress.