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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED PLANT GENETIC RESOURCES FOR PASTURES AND RANGELANDS IN THE TEMPERATE SEMIARID REGIONS OF THE WESTERN U.S. Title: Enhanced tolerance to NaC1 and LiC1 stresses by over-expressing Caragana korshinskii sodium/proton exchange 1 (CkNHX1) and the hydrophilic C terminus is required for the activity of CkNHX1 in Atsos3-1 mutant and yeast

Authors
item Yang, D -
item Song, L -
item Hu, J -
item Yin, W -
item Wang, Richard
item Hu, Z -
item Wei-Bo, L -
item Zhi-Guo, C -
item Yu-Hong, S -
item Xiao, H -

Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 6, 2011
Publication Date: January 17, 2012
Citation: Yang, D.H., Song, L.Y., Hu, J., Yin, W.B., Wang, R., Hu, Z.M., Wei-Bo, L., Zhi-Guo, C., Yu-Hong, S., Xiao, H. 2012. Enhanced tolerance to NaC1 and LiC1 stresses by over-expressing Caragana korshinskii sodium/proton exchange 1 (CkNHX1) and the hydrophilic C terminus is required for the activity of CkNHX1 in Atsos3-1 mutant and yeast. Biochem Biophys Res Comm. 417:732-737.

Interpretive Summary: Plants' tolerance to salt can be controlled by different genetic mechanisms that regulate varying biochemical pathways. One of these is the gene NHX controlling sodium/proton exchangers (NHX antiporters). A pea shrub, Caragana korshinskii, is known to tolerate salt, drought, and cold stresses. The NHX gene in this species, named CkNHX1, was isolated and studied. We demonstrated that expression of CkNHX1 significantly enhanced the resistance to NaC1 and LiC1 stresses. Furthermore, the gene product CkNHX1 is mainly present in roots and its hydrophilic C-terminal region is required for Na+/H+ exchanging activity. These findings provide clues to explain this shrub's tolerance to NaC1 and LiC1 salts.

Technical Abstract: Sodium/proton exchangers (NHX antiporters) play important roles in plant responses to salt stress. Previous research showed that hydrophilic C-terminal region of Arabidopsis AtNHX1 negatively regulates the Na+/H+ transporting activity. In this study, CkNHX1 were isolated from Caragana korshinskii, a pea shrub with high tolerance to salt, drought, and cold stresses. Transcripts of CkNHX1 were detected predominantly in roots, and were significantly induced by NaC1 stress in stems. Transgenic yeast and Arabidopsis thaliana sos3-1 (Atsos3-1) mutant over-expressing CkNHX1 and its hydrophilic C terminus-truncated derivative, CkNHX1-^C, were generated and subjected to NaC1 and LiC1 stresses. Expression of CkNHX1 significantly enhanced the resistance to NaC1 and LiC1 stresses in yeast and Atsos3-1 mutant. Whereas, compared with expression of CkNHX1, the expression of CkNHX1-^C had much less effect on NaC1 tolerance in Atsos3-1 and LiC1 tolerance in yeast and Atsos3-1. All together, these results suggest that the predominant expression of CkNHX1 in roots might keep C. korshinskii adapting to the high salt condition in this plant's living environment; CkNHX1 could recover the phenotype of Atsos3-1 mutant; and the hydrophilic C-terminal region of CkNHX1 is required for Na+/H+ and Li+/H+ exchanging activity of CkNHX1.

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