Summary of Current and Future Research:

The research is conducted in two main directions: one is concerned with the gene csa and its encoded protein phospholipid hydroperoxide glutathione peroxidase, and the other is aimed at elucidation of the role of lipid metabolism in salt tolerance.

We have isolated the promoter of csa fused it to GUS as a reporter gene and used it for transformation of cultured tobacco cells as well as tobacco plants. In addition, we prepared two deletion constructs of the promoter and we are currently quantifying the expression of GUS under various stress conditions, and trying to identify promoter regions required for its expression.

We characterized a 9-lipoxygenase activity in citrus cells, which is transiently induced by salt. We are currently studying the expression of the protein and its relation to salt tolerance.

We have found salt-induced changes in the degree of fatty acid unsaturation in salt-tolerant cells only, and we are currently trying to find out its relationship to salt stress and salt-tolerance.*

Relevant Publications:
(Complete list available)

1. Ben-Hayyim, G., Faltin, Z., Gepstein, S., Camoin, L., Strosberg, A. D. and Eshdat, Y. (1993). Isolation and characterization of salt-associated protein in Citrus. Plant Sci.88:129-140.
2. Holland, D., Ben-Hayyim, G., Faltin, Z., Camoin, L., Strosberg, A.D.and Eshdat, Y. (1993). Molecular characterization of salt-stress associated protein in citrus: protein and cDNA sequence homology to mammalian glutathione peroxidases. Plant Mol.Biol.21:923-927.
3. Holland, D., Ben-Hayyim, G., Faltin, Z., Camoin, L., Strosberg, A.D. and Eshdat, Y. (1993). Primary sequence of Cit-SAP from Citrus sinensis.Plant Mol.Biol.21:738.
4. Holland, D., Eshdat, Y. Faltin, Z. and Ben-Hayyim, G. (1993) Molecular cloning of csa, a gene from citrus encoding a protein potentially involved in the defencse against oxidative stress. Acta Hort.329:228-230.
5. Yermiyahu, U., Nir, S., Ben-Hayyim, G. and Kafkafi, U. (1994) Quantitative competition of calcium with sodium or magnesium for sorption sites on plasma membrane vesicles of melon (Cucumis meloL.) root cells. J.Membrane Biol.138:55-63.
6. Gabbay-Azaria, R., Pick, U., Ben-Hayyim, G. and Tel-Or, E. (1994) The involvement of a vanadate-sensitive ATPase in plasma membrane of a marine cyanobacterium in salt tolerance. Physiol. Plant.90:692-698.
7. Holland, D., Faltin, Z., Perl, A. , Ben-Hayyim, G. and Eshdat, Y. (1994) A novel plant glutathione peroxidase like protein provides tolerance to oxygen radicals generated by paraquat in Escherichia coli.FEBS Letters337:52-55.
8. Libal-Weksler, Y., Nir, M., Ben-Hayyim, G. and Tel-Or E. (1994) Starch metabolism in salt tolerant and salt sensitive Shamouti callus. Plant Physiol. Biochem.32:655-659.
9. Naot, D., Ben-Hayyim, G., Eshdat, Y. and Holland, D. (1995) Drought, heat and salt stress induce the expression of a citrus homologue of an atypical late embryogenesis Lea5 gene.Plant Mol.Biol.27:619-622.
10. Naot, D., Holland, D., Avsian-Kretchmer, O., Eshdat, Y. and Ben-Hayyim, G. (1995) Induction of gene encoding an oleosin homologue in cultured citrus cells exposed to salt stress. Gene161:171-173.
11. Beeor-Tzahar, T., Ben-Hayyim, G., Holland, D., Faltin, Z. and Eshdat, Y. (1995) A stress associated citrus protein is a distinct plant phospholipid hydroperoxide glutathione peroxidase. FEBS Lett.366:151-155.
12. Ben-Hayyim, G., Martin-Tanguy, J. and Tepfer D, (1996) Changing root and shoot architecture with the rolA gene from Agrobacterium rhizogenes: interaction with gibberellic acid and polyamine metabolism. Physiol. plant.96:237-243.
13. Eshdat, Y., Holland, D., Faltin, Z., Ben-Hayyim, G. (1997) Plant glutathione peroxidasesPhysiol. Plant.100: 234-240
14. Gueta-Dahan, Y., Yaniv, Z., Zilinskas, B.A. and Ben-Hayyim, G. (1997) Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in citrus. Planta203:460-469
15. Yermiyahu, U., Nir, S., Ben-Hayyim, G., Kafkafi, U. and Kinraide, B. (1997) Root elongation in saline solution related to calcium binding to root cell plasma membranes. Plant and Soil191:67-76
16. Faltin, Z., Camoin, L., Ben-Hayyim, G., Perl, A., Beeor-Tzahar, T., Stosberg, A.D., Holland, D. and Eshdat, Y. (1998) Cysteine Is the presumed catalytic residue of Citrus sinensis phospholipid hydroperoxide glutathione peroxidase over-expressed under salt stress. Physiol. Plant. 104: 741-746
17. Avsian-Kretchmer, O., Eshdat, Y., Gueta-Dahan, Y., Ben-Hayyim, G. (1999) Regulation of stress-induced phospholipid hydroperoxide glutathione peroxidase expression in citrus. Planta 209: 469-477
18. Bin, Y., Faltin, Z., Ben-Hayyim, G., Eshdat, Y., Gressel, J. (2000) Correlation of glutathione peroxidase to paraquat/oxidative stress resistance in Conyzadetermined by direct fluorometric assay. Pesticided Biochemistry and Physiology66:182-194