N 52. Functional Characterization of SlNhaD1, a Cation/H+ Antiporter from Tomato,
and Its Implication in Salt Tolerance
Olías R., Li J., Alvarez de Morales P., Eljakaoui Z., Morales S., de Dios Alché J.,
Benito B., Belver A.
Maintaining a high K+/Na+ ratio in the cell cytosol is a key aspect in plant salt
tolerance. In this context, K+, Na+, and H+ transporters play a crucial role. We have
identified and cloned a SlNhaD1 gene from tomato ( Solanum lycopersicum L.).
Homology-based searches revealed that this gene encodes a putative Na+/H+
antiporter. Analysis of the amino acid sequence of SlNhaD1 predicted the presence
of both a chloroplast transit peptide and a 12-13 transmembrane domains.
Experiments of SlNhaD1-GFP transient expression in Nicotiana benthamiana
showed the fluorescence mainly localized in several types of plastids present all
throughout plant organs. Preliminary results of characterization in heterologous
system were carried out using the E. coli TKW4205 strain, which is deficient in all K+
transporters. In this system, the SlNhaD1 protein was able to restore the strain
growth under K+-deficient conditions. In addition, virus-induced silencing (VIGS)
was used for in planta functional characterization of SlNhaD1. Phenotype evaluation
of tomato plants under saline conditions is being carried out in order to determine the
importance of this protein in salt tolerance. Our results suggest that
SlNhaD1 plays an important role in plastid ion homeostasis.