Molecular Cloning of Saslah3, a Novel Slow Anion Channel Slac/slah Family Gene, From Euhalophyte Suaeda Altissima (L.) Pall and Analysis of the Encoded Protein

Abstract Cloning of the SaSLAH3 gene (OQ271227.1), an AtSLAH3 ortholog from the slow anion channels family (SLAC/SLAH), that was originally identified in Arabidopsis thaliana, has been carried out from the euhalophyte Suaeda altissima. Under hydroponic conditions, this species related to Amaranthaceae/Chenopodiaceae is capable to complete life cycle on nutrient solutions containing NaCl at high concentrations up to 1 M. Cloning of SaSLAH3 was performed based on a putative similarity of SaSLAH3 with the SLAH3 homologs from the related species Suaeda glauca and Suaeda fruticosa, using transcriptomes assembled previously. Membrane topology, analyzed by in silico approach, the 3-D structure, presence of conservative phenylalanine-bearing motives and as well as MEME-generated sequence motif patterns of SaSLAH3, all of these features were found typical for the SLAC/SLAH channels and had validated SaSLAH3 belonging to this family. Analysis of SLAC/SLAH phylogenetic relationship demonstrated the evolutionary divergence of SLAC-like proteins into three distinct groups characteristic of this family with location of SaSLAH3 in SLAH2/3 clade. Investigation of the expression profile by quantitative Real-Time PCR revealed increasing SaSLAH3 expression in roots and leaves upon elevation of NaCl concentration in nutrient solution under conditions of both sufficient nitrate supply and nitrate deficiency. SaSLAH3 is suggested to play an important role in enhancing chloride loading into root xylem and, thereafter in chloride delivery to shoot under salinity. Another physiological role of SaSLAH3 may be attributed to regulation of nitrate concentration in cytoplasm to ensure proper nitrogen nutrition of S. altissima plants under conditions of stiff competition of nitrate with chloride.