Molecular and functional analyses of rice NHX-type Na+/H+ antiporter genes
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We previously cloned a vacuolar Na+/H+ antiporter gene (OsNHX1) from rice (Oryza sativa). Here we identified four additional NHX-type antiporter genes in rice (OsNHX2 through OsNHX5) and performed molecular and functional analyses of those genes. The exon–intron structure of the OsNHX genes and the phylogenetic tree of the OsNHX proteins suggest that the OsNHX proteins are categorized into two subgroups (OsNHX1 through OsNHX4 and OsNHX5). OsNHX1, OsNHX2, OsNHX3, and OsNHX5 can suppress the Na+, Li+, and hygromycin sensitivity of yeast nhx1 mutants and their sensitivity to a high K+ concentration. The expression of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 is regulated differently in rice tissues and is increased by salt stress, hyperosmotic stress, and ABA. When we studied the expression of β-glucuronidase (GUS) driven by either the OsNHX1 or the OsNHX5 promoter, we observed activity in the stele, the emerging part of lateral roots, the vascular bundle, the water pore, and the basal part of seedling shoots with both promoters. In addition, each promoter had a unique expression pattern. OsNHX1 promoter–GUS activity only was localized to the guard cells and trichome, whereas OsNHX5 promoter–GUS activity only was localized to the root tip and pollen grains. Our results suggest that the members of this gene family play important roles in the compartmentalization into vacuoles of the Na+ and K+ that accumulate in the cytoplasm and that the differential regulation of antiporter gene expression in different rice tissues may be an important factor determining salt tolerance in rice.
KeywordsGene expression Na+/H+ antiporter gene Oryza Salt tolerance
Basic-domain leucine zipper
Expressed sequence tag
P1-derived artificial chromosome
Rapid amplification of cDNA ends
Rice Genome Research Program
We thank Dr. Rajini Rao (Johns Hopkins University, USA) for kindly providing the yeast strains, K601 and R100. We also thank Drs. I. Mitsuhara and Y. Ohashi for kindly providing the vectors, pTN2 and pE2113–GUS. The cDNA clones including OsNHX2 and OsNHX5 and PAC clones including OsNHX1 and OsNHX5 were gifts from the Rice Genome Research Program. We thank Drs. Y. Nagamura and M. Yano for technical advice. We also thank C. Tsuiki, K. Toyoshima, T. Kataoka, and S. Li for technical assistance. This work was supported by Grants-in-Aid from the Ministry of Agriculture, Forestry and Fisheries of Japan (Development of Innovative Transgenic Plants no.2113 and Rice Genome Project MP-2126).
- Fukuoka H, Ogawa T, Mitsuhara I, Iwai T, Isuzugawa K, Nishizawa Y, Gotoh Y, Nishizawa Y, Tagiri A, Ugaki M, Ohshima M, Yano H, Murai N, Niwa Y, Hibi T, Ohashi Y (2000) Agrobacterium-mediated transformation of monocot and dicot plants using the NCR promoter derived from soybean chlorotic mottle virus. Plant Cell Rep 19:815–820CrossRefGoogle Scholar
- Gietz RD, Schiestl RH (1995) Transforming yeast with DNA. Methods Mol Cell Biol 5:255–269Google Scholar
- Goff SA, Ricke D, Lan T-H, Presting G, Wang R, Dunn M, Glazebrook J, Sessions A, Oeller P, Varma H, Hadley D, Hutchison D, Martin C, Katagiri F, Lange BM, Moughamer T, Xia Y, Budworth P, Zhong J, Miguel T, Paszkowski U, Zhang S, Colbert M, Sun W, Chen L, Cooper B, Park S, Wood TC, Mao L, Quail P, Wing R, Dean R, Yu Y, Zharkikh A, Shen R, Sahasrabudhe S, Thomas A, Cannings R, Gutin A, Pruss D, Reid J, Tavtigian S, Mitchell J, Eldredge G, Scholl T, Miller RM, Bhatnagar S, Adey N, Rubano T, Tusneem N, Robinson R, Feldhaus J, Macalma T, Oliphant A, Briggs S (2002) A draft sequence of the rice genome (Oryza sativa L. ssp. japonica). Science 296:92–100CrossRefPubMedGoogle Scholar
- Mitsuhara I, Ugaki M, Hirochika H, Ohshima M, Murakami T, Gotoh Y, Katayose Y, Nakamura S, Honkura R, Nishimiya S, Ueno K, Mochizuki A, Tanimoto H, Tsugawa H, Otsuki Y, Ohashi Y (1996) Efficient promoter cassettes for enhanced expression of foreign genes in dicotyledonous and monocotyledonous plants. Plant Cell Physiol 37:49–59PubMedGoogle Scholar
- Sze H, Padmanaban S, Cellier F, Honys D, Cheng N-H, Bock KW, Conéjéro G, Li X, Twell D, Ward JM, Hirschi KD (2004) Expression patterns of a novel AtCHX gene family highlight potential roles in osmotic adjustment and K+ homeostasis in pollen development. Plant Physiol 136:2532–2547CrossRefPubMedGoogle Scholar