Characterization of a novel potato gene coding for a putative RNA binding protein involved in plant response to water stress.

Plants respond to abiotic stresses by complex mechanisms involving a wide gene network. In order to preserve productivity of species in adverse environmental conditions is crucial to identify and characterize molecular functions that regulate the stress response and, above all, the adaptative response. Previously, we reported a transcriptome analysis of potato cell exposed to short (shock) and long- term (acclimation) water stress induced by PolyEthyleneGlycole. Comparison of two different responses was performed by the TIGR 10k potato array challenged with RNA isolated from untreated, PEG-shocked and PEG-acclimated cells (Ambrosone et al. 2006, proceedings of SIGA annual congress). Among the genes consistently induced during long- term water deficit the EST AW906734 coding for gene sato2, acronimous of SAlt Tolerance, was identified. Sato2 gene encodes for a protein conferring salt resistance by complementation of a yeast defective mutant (Ros et al. unpublished) and contains a conserved RNA-binding protein domain.We isolated the sato2 coding sequence of S. tuberosum by RT-PCR using primer designed on sato2 tentative consensus of S. lycopersicum. Sequence translation and BlastP search reveals that the protein is highly conserved with more than 60% homology in several species as B. vulgaris, V. faba, S. olearia and A. thaliana. Gene expression of sato2 was accurately investigated in potato cells, leaves and roots by qRT- PCR confirming the gene is responsive to water deficit conditions. A characterization of the A. thaliana sato hortologous gene (Atsato, At4g16830) was carried out. At4g16830 is a nuclear RNA-binding protein of 355 aa containing a RGG box with unknown function (www.arabidopsis.org). The gene resulted up- regulated in Arabidopsis cells exposed to 50 uM ABA, 150 mM NaCl and 10% PEG. Phenotypic and physiological analysis of Atsato knockout (Atsato KO) indicated that the mutant was severely affected by ABA, NaCl and PEG treatments. In particular, root elongation of Atsato KO was inhibited in presence of 80 mM NaCl and in PEG treatments compared to wt Columbia (Col-0) genotype. To investigate the localization of the SATO2, transgenic plants overexpressing YFP fusion protein was obtained. The SATO2::YFP-fluorescence signal revealed SATO2 localizes in cytoplasm of arabidopsis cells. We utilized promoter GUS fusion to understand the genetic regulation of sato2 in arabidopsis. GUS expression was found in leaves, petals, sepals, stomata and pollen. Gain of function and molecular interaction studies are in progress to establish the functional role of sato in water stress response.