References

Adams, P., Nelson, D. E., Yamada, S., Chmara, W., Jensen, R. G., Bohnert, H. J., and Griffiths, H. (1998). Growth and development of Mesembryanthemum crystallinum (Aizoaceae). New Phytol. 138, 171–190.

Aharon, G. S., Apse, M. P., Duan, S., Hua, X., and Blumwald, E. (2003). Characterization of a family of vacuolar Na+ /H+ antiporters in Arabidopsis thaliana. Plant Soil 253, 245–256.

Akashi, K., Miyake, C., and Yokota, A. (2001). Citrulline, a novel compatible solute in drought-tolerant wild watermelon leaves, is an efficient hydroxyl radical scavenger. FEBS Lett. 508, 438–442.

Akashi, K., Nishimura, N., Ishida, Y., and Yokota, A. (2004). Potent hydroxyl radical-scavenging activity of drought-induced type-2 metallothionein in wild watermelon. Biochem. Biophys. Res. Commun. 323, 72–78.

Alvim, F. C., Carolino, S. M., Cascardo, J. C., Nunes, C. C., Martinez, C. A., Otoni, W. C., and Fontes, E. P. (2001). Enhanced accumulation of BiP in transgenic plants confers tolerance to water stress. Plant Physiol. 126, 1042–1054.

Amtmann, A., and Sanders, D. (1999).Mechanisms of Na+ uptake by plant cells. Adv. Bot. Res. 29, 75–112.

Apse, M. P., and Blumwald, E. (2002). Engineering salt tolerance in plants. Curr. Opin. Biotech. 31, 146–150.

Apse, M. P., Aharon, G. S., Snedden, W. A., and Blumwald, E. (1999). Salt tolerance conferred by overexpression of a vacuolar Na+ /H+ antiport in Arabidopsis. Science 285, 1256–1258.

Arabidopsis Genome Initiative (2000). Analysis of the genome sequence of the flowering plant Arabidopsis thaliana. Nature 408, 796–815.

Arango, M., Gévaudant, F., Oufattole, M., and Boutry, M. (2003). The plasma membrane proton pump ATPase, the significance of gene subfamilies. Planta 216, 355–365.

Audran, C., Borel, C., Frey, A., Sotta, B., Meyer, C., Simonneau, T., and Marion-Poll, A. (1998). Expression studies of the zeaxanthin epoxidase gene in Nicotiana plumbaginifolia. Plant Physiol. 118, 1021–1028.

Bennetzen, J. (2002). The rice genome. Opening the door to comparative plant biology. Science 296, 60–63.

Berthomieu, P., Conéjéro, G., Nublat, A., Brackenbury, W. J., Lambert, C., Savio, C., Uozumi, N., Oiki, S., Yamada, K., Cellier, F., Gosti, F., Simonneau, T., et al. (2003). Functional analysis of AtHKT1 in Arabidopsis shows that Na þ recirculation by the phloem is crucial for salt tolerance. EMBO J. 22, 2004–2014.

Blumwald, E. (2000). Sodium transport and salt tolerance in plants. Curr. Opin. Cell Biol. 12, 431–434.

Blumwald, E., Aharon, G. S., and Apse, M. P. (2000). Sodium transport in plant cells. Biochim. Biophys. Acta 1465, 140–151.

Bohnert, H. J., and Bressan, R. A. (2001). Abiotic stresses, plant reactions, and approaches towards improving stress tolerance. In ‘‘Crop Science, Progress and Prospects’’ (J. No¨ssberger, H. H. Geiger, and P. C. Struik, eds.), pp. 81–100. CABI International, Wallingford, UK. Bohnert, H. J., and Shen, B. (1999). Transformation and compatible solutes. Sci. Horticult. 78, 237–260.

Borsani, O., Cuartero, J., Ferna´ndez, J. A., Valpuesta, V., and Botella, M. A. (2001). Identification of two loci in tomato reveals distinct mechanisms for salt tolerance. Plant Cell 13, 873–887.

Bressan, R. A., Zhang, C., Zhang, H., Hasegawa, P. M., Bohnert, H. J., and Zhu, J. K. (2002). Learning from the Arabidopsis experience. The next gene search paradigm. Plant Physiol. 127, 1354–1360.

Chang, L., and Karin, M. (2001). Mammalian MAP kinase signaling cascades. Nature 410, 37–40.

Cheeseman, J. M. (1988). Mechanisms of salinity tolerance in plants. Plant Physiol. 87, 547–550.

Cheng, N.-H., Pittman, J. K., Barkla, B. J., Shigaki, T., and Hirschi, K. D. (2003). The Arabidopsis cax1 mutant exhibits impaired ion homeostasis, development, and hormonal responses and reveals interplay among vacuolar transporters. Plant Cell 15, 347–364.

Cherel, I., Michard, E., Platet, N., Mouline, K., Alcon, C., Sentenac, H., and Thibaud, J. B. (2002). Physical and functional interaction of the Arabidopsis K þ channel AKT2 and phosphatase AtPP2CA. Plant Cell 14, 1133–1146.

Chinnusamy, V., Schumaker, K., and Zhu, J.-K. (2004). Molecular genetic perspectives on cross-talk and specificity in abiotic stress signaling in plants. J. Exp. Bot. 55, 225–236.

Condon, A. G., Richards, R. A., Rebetzke, G. J., and Farquhar, G. D. (2004). Breeding for high water-use efficiency. J. Exp. Bot. 55, 2447–2460.

Cramer, G. R., Lynch, J. L., Lau¨ chli, A., and Epstein, E. (1987). Influx of Na+ , K+ , and Ca2+ into roots of salt-stressed cotton seedling. Effects of supplemental Ca2+ . Plant Physiol. 83, 510–516.

Cushman, J. C., and Bohnert, H. J. (2000). Genomic approaches to plant stress tolerance. Curr. Opin. Plant Biol. 3, 117–124.

Dambly, S., and Boutry, M. (2001). The two major plant plasma membrane H+ -ATPase display different regulatory properties. J. Biol. Chem. 276, 7017–7022.

Davenport, R. J., and Tester, M. (2000). A weakly voltage-dependent, nonselective cation channel mediates toxic sodium influx in wheat. Plant Physiol. 122, 823–834.

Demidchik, V., and Tester, M. (2002). Sodium fluxes through nonselective cation channels in the plasma membrane of protoplasts from Arabidopsis roots. Plant Physiol. 128, 379–387.

Demidchik, V., Davenport, R. J., and Tester, M. (2002). Nonselective cation channels in plants. Annu. Rev. Plant Biol. 53, 67–107.

Eastmond, P. J., and Graham, I. A. (2003). Trehalose metabolism: A regulatory role for trehalose-6- phosphate? Curr. Opin. Plant Biol. 6, 231–235.

Ellul, P., Rios, G., Atares, A., Roig, L. A., Serrano, R., and Moreno, V. (2003). The expression of the Saccharomyces cerevisiae HAL1 gene increases salt tolerance in transgenic watermelon [Citrullus lanatus (Thunb.) Matsun. & Nakai.]. Theor. Appl. Genet. 107, 462–469.

Elumalai, R. P., Nagpal, P., and Reed, J. W. (2002). A mutation in the Arabidopsis KT2/KUP2 potassium transporter gene affects shoot cell expansion. Plant Cell 14, 119–131.

Epstein, E. (1961). The essential role of calcium in selective cation transport by plant cells. Plant Physiol. 36, 437–444.

Essah, P. A., Davenport, R., and Tester, M. (2003). Sodium influx and accumulation in Arabidopsis. Plant Physiol. 133, 307–318.

Flowers, T. J. (2004). Improving crop salt tolerance. J. Exp. Bot. 55, 307–319.

Flowers, T. J., and Yeo, A. R. (1992). ‘‘Solute Transport in Plants,’’ pp. 1–176. Blackie Academic & Professional, London.

Flowers, T. J., and Yeo, A. R. (1995). Breeding for salinity resistance in crop plants, where next? Aust. J. Plant Physiol. 22, 875–884.

Flowers, T. J., Hajibagheri, M. A., and Clipson, N. J. W. (1986). Halophytes. Quart. Rev. Biol. 61, 313–337.

Garciadeblas, B., Rubio, F., Quintero, F. J., Banuelos, M. A., Haro, R., and Rodriguez-Navarro, A. (1993). Differential expression of two genes encoding isoforms of the ATPase involved in sodium efflux in Saccharomyces cerevisiae. Mol. Gen. Genet. 236, 363–368.

Garciadeblas, B., Senn, M. E., Banuelos, M. A., and Rodriguez-Navarro, A. (2003). Sodium transport and HKT transporters, the rice model. Plant J. 34, 788–801.

Garg, A. K., Kim, J. K., Owens, T. G., Ranwala, A. P., Choi, Y. D., Kochian, L. V., and Wu, R. J. (2002). Trehalose accumulation in rice plants confers high tolerance levels to different abiotic stresses. Proc. Natl. Acad. Sci. USA 99, 15898–15903.

Gaxiola, R. A., Rao, R., Sherman, A., Grisafi, P., Alper, S. L., and Fink, G. R. (1999). The Arabidopsis thaliana proton transporters, AtNhx1 and Avp1, can function in cation detoxification in yeast. Proc. Natl. Acad. Sci. USA 96, 1480–1485.

Gaxiola, R. A., Li, J., Undurrage, S., Dang, L. M., Allen, G. J., Alper, S. L., and Fink, G. R. (2001). Drought- and salt-tolerant plants result from overexpression of the AVP1 H+ -pump. Proc. Natl. Acad. Sci. USA 98, 11444–11449.

Gaxiola, R. A., Fink, G. R., and Hirschi, K. D. (2002). Genetic manipulation of vacuolar proton pumps and transporters. Plant Physiol. 129, 967–973.

Gisbert, C., Rus, A. M., Bolarin, M. C., Lopez-Coronado, J. M., Arrillaga, I., Montesinos, C., Caro, M., Serrano, R., and Moreno, V. (2000). The yeast HAL1 gene improves salt tolerance of transgenic tomato. Plant Physiol. 123, 393–402.

Glenn, E., Brown, J. J., and Blumwald, E. (1999). Salt tolerance and crop potential of halophytes. Crit. Rev. Plant Sci. 18, 227–255.

Goff, S. A., Ricke, D., Lan, T. H., Presting, G., Wang, R., Dunn, M., Glazebrook, J., Sessions, A., Oeller, P., Varma, H., Hadley, D., Hutchison, D., et al. (2002). A draft sequence of the rice genome (Oryza sativa L. ssp. japonica). Science 296, 92–100.

Greenway, H., and Osmond, C. B. (1972). Salt responses of enzymes from species differing in salt tolerance. Plant Physiol. 49, 256–259.

Grillo, S., Leone, A., Xu, Y., Tucci, M., Francione, R., Hasegawa, P. M., Monti, L., and Bressan, R. A. (1995). Control of osmotin gene expression by ABA and osmotic stress in vegetative tissues of wildtype and ABA-deficient mutants of tomato. Physiol. Plant 93, 498–504.

Guo, Y., Halfter, U., Ishitani, M., and Zhu, J. K. (2001). Molecular characterization of functional domains in the protein kinase sos2 that is required for plant salt tolerance. Plant Cell 13, 1383–1400.

Hasegawa, P. M., Bressan, R. A., and Pardo, J. M. (2000a). The dawn of plant salt to tolerance genetics. Trends Plant Sci. 5, 317–319.

Hasegawa, P. M., Bressan, R. A., Zhu, J.-K., and Bohnert, H. J. (2000b). Plant cellular and molecular responses to high salinity. Annu. Rev. Plant Physiol. Plant Mol. Biol. 51, 463–499.

Hayashi, H., Alia, Mustardy, L., Deshnium, P., Ida, M., and Murata, N. (1997). Transformation of Arabidopsis thaliana with the coda gene for choline oxidase; accumulation of glycinebetaine and enhanced tolerance to salt and cold stress. Plant J. 12, 133–142.

Henikoff, S., Till, B. J., and Comai, L. (2004). Tilling. Traditional mutagenesis meets functional genomics. Plant Physiol. 135, 630–636.

Hill, A. E., Shachar-Hill, B., and Shachar-Hill, Y. (2004). What are aquaporins for? J.Membr. Biol. 197, 1–32.

Himmelbach, A., Yang, Y., and Grill, E. (2003). Relay and control of abscisic acid signaling. Curr. Opin. Plant Biol. 6, 470–479.

Hirschi, K. D. (2004). The calcium conundrum. Both versatile nutrient and specific signals. Plant Physiol. 136, 2438–2442.

Hohmann, S. (2002). Osmotic stress signaling and osmoadaptation in yeasts. Microbiol. Mol. Biol. Rev. 66, 300–372.

Holmstrom, K. O., Somersalo, S., Mandal, A., Palva, T. E., and Welin, B. (2000). Improved tolerance to salinity and low temperature in transgenic tobacco producing glycine betaine. J. Exp. Bot. 51, 177–185.

Hong, Z., Lakkineni, K., Zhang, Z., and Verma, D. P. (2000). Removal of feedback inhibition of delta(1)- pyrroline-5-carboxylate synthetase results in increased proline accumulation and protection of plants from osmotic stress. Plant Physiol. 122, 1129–1136.

Horie, T., and Schroeder, J. I. (2004). Sodium transporters in plants. Diverse genes and physiological functions. Plant Physiol. 136, 2457–2462.

Hoth, S., Morgante, M., Sanchez, J. P., Hanafey, M. K., Tingey, S. V., and Chua, N. H. (2002). Genomewide gene expression profiling in Arabidopsis thaliana reveals new targets of abscisic acid and largely impaired gene regulation in the abi1–1 mutant. J. Cell Sci. 115, 4891–4900.

Hugouvieux, V., Kwan, J. M., and Schroeder, J. I. (2001). An mRNA binding protein, ABH1, modulates early abscisic acid signal transduction in Arabidopsis. Cell 106, 477–487.

Hugouvieux, V., Murata, Y., Young, J. J., Kwak, J. M., Mackesy, D. Z., and Schroeder, J. I. (2002). Localization, ion channel regulation, and genetic interactions during abscisic acid signaling of the nuclear mRNA cap-binding protein, ABH1. Plant Physiol. 130, 1276–1287.

Ichimura, K., Mizoguchi, T., Yoshida, R., Yuasa, T., and Shinozaki, K. (2000). Various abiotic stresses rapidly activate Arabidopsis MAP kinases ATMPK4 and ATMPK6. Plant J. 24, 655–665.

Inan, G., Zhang, Q., Li, P., Wang, Z., Cao, Z., Zhang, H., Zhang, C., Quist, T. M., Goodwin, S. M., Zhu, J., Shi, H., Damsz, B., et al. (2004). Salt cress. A halophyte and cryophyte Arabidopsis relative model system and its applicability to molecular genetic analyses of growth and development of extremophiles. Plant Physiol. 135, 1718–1737.

Ingram, J., and Bartels, D. (1996). The molecular basis of dehydration tolerance in plants. Annu. Rev. Plant Physiol. Plant Mol. Biol. 48, 377–403.

Ishitani, M., Xiong, L., Stevenson, B., and Zhu, J. K. (1997). Genetic analysis of osmotic and cold stress signal transduction in Arabidopsis, interactions and convergence of abscisic acid-dependent and abscisic acid-independent pathways. Plant Cell 9, 1935–1949.

Iuchi, S., Kobayashi, M., Yamaguchi-Shinozaki, K., and Shinozaki, K. (2000). A stress-inducible gene for 9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis under water stress in drought-tolerant cowpea. Plant Physiol. 123, 553–562.

Jacoby, B. (1999). Nutrient uptake in plants. In ‘‘Handbook of Plant and Crop Stress’’ (M. Pessarakli, ed.), pp. 1–23. Dekker, New York.

Jang, I. C., Oh, S. J., Seo, J. S., Choi, W. B., Song, S. I., Kim, C. H., Kim, Y. S., Seo, H. S., Choi, Y. D., Nahm, B. H., and Kim, J. K. (2003). Expression of a bifunctional fusion of the Escherichia coli genes for trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase in transgenic rice plants increases trehalose accumulation and abiotic stress tolerance without stunting growth. Plant Physiol. 131, 516–524.

Jeong, M. J., Park, S. C., and Byun, M. O. (2001). Improvement of salt tolerance in transgenic potato plants by glyceraldehyde-3-phosphate dehydrogenase gene transfer. Mol. Cell 12, 185–189.

Jonak, C.,ö kre´sz, L., Bo¨gre, L., and Hirt, H. (2002). Complexity, cross talk and integration of plant MAP kinase signaling. Curr. Opin. Plant Biol. 5, 415–424.

Jung, K., Veen, M., and Altendorf, K. (2000). K þ and ionic strength directly influence the autophosphorylation activity of the putative turgor sensor KdpD of Escherichia coli. J. Biol. Chem. 275, 40142–40147.

Kasuga, M., Liu, Q., Miura, S., Yamaguchi-Shinozaki, K., and Shinozaki, K. (1999). Improving plant drought, salt, and freezing tolerance by gene transfer of a single stress-inducible transcription factor. Nat. Biotechnol. 17, 287–291.

Kishor, P., Hong, Z., Miao, G. H., Hu, C., and Verma, D. (1995). Overexpression of [delta]-pyrroline-5- carboxylate synthetase increases proline production and confers osmotolerance in transgenic plants. Plant Physiol. 108, 1387–1394.

Knight, H., Trewavas, A. J., and Knight, M. R. (1997). Calcium signaling in Arabidopsis thaliana responding to drought and salinity. Plant J. 12, 1067–1078.

Koiwa, H., Barb, A. W., Xiong, L., Li, F., Mcculy, M. G., Lee, B. H., Sokolchik, I., Zhu, J., Gong, Z., and Reddy, M. (2002). C-terminal domain phosphatase-like family members (AtCPLs) differentially regulate Arabidopsis thaliana abiotic stress signaling, growth, and development. Proc. Natl. Acad. Sci. USA 99, 10893–10898.

Koiwa, H., Hausmann, S., Bang, W. Y., Ueda, A., Kondo, N., Hiraguri, A., Fukuhara, T., Bahk, J. D., Yun, D. J., Bressan, R. A., Hasegawa, P. M., and Shuman, S. (2004). Arabidopsis C-terminal domain phosphatase-like 1 and 2 are essential Ser-5-specific C-terminal domain phosphatases. Proc. Natl. Acad. Sci. USA 101, 14539–14544.

Koyama, M. L., Levesley, A., Koebner, R. M. D., Flowers, T. J., and Yeo, A. R. (2001). Quantitative trait loci for component physiological traits determining salt tolerance in rice. Plant Physiol. 125, 406–422.

Kurkela, S., and Franck, M. B. (1990). Cloning and characterization of a cold- and ABA-inducible Arabidopsis gene. Plant Mol. Biol. 15, 137–144.

Läuchli, A. (1996). Salinity—Potassium interaction in crop plants. In ‘‘Frontiers in Potassium Nutrition, New Perspectives on the Effects of Potassium on Physiology of Plants’’ (D. M. Oosterhuis, and G. A. Berkowitz, eds.), pp. 71–76. Proceeding of a Symposium, published by the Potash&Phosphate Institute/Potash & Phosphate Institute of Canada.

Läuchli, A., and Epstein, E. (1990). Plant responses to saline and sodic conditions. In ‘‘Salinity Assessment and Management’’ (K. K. Tanji, ed.), pp. 113–137. Amer. Soc. Civil Eng., New York.

Laurie, S., Feeney, K. A., Maathuis, F. J. M., Heard, P. J., Brown, S. J., and Leigh, R. A. (2002). A role for HKT1 in sodium uptake by wheat roots. Plant J. 32, 139–149.

Lee, E. K., Kwon, M., Ko, J. H., Yi, H., Hwang, M. G., Chang, S., and Cho, M. H. (2004). Binding of sulfonylurea by AtMRP5, an Arabidopsis multidrug resistance-related protein that functions in salt tolerance. Plant Physiol. 134, 528–538.

Li, J., Lee, Y. R. J., and Assmann, S. M. (1998). Guard cells possess a calcium-dependent protein kinase that phosphorylates the KAT1 potassium channel. Plant Physiol. 116, 785–795.

Lin, H. X., Zhu, M. Z., Yano, M., Gao, J. P., Liang, Z. W., Su, W. A., Hu, X. H., Ren, Z. H., and Chao, D. Y. (2004). QTLs for Na þ and K þ uptake of the shoots and roots controlling rice salt tolerance. Theor. Appl. Genet. 108, 253–260.

Loudet, O., Chaillou, S., Krapp, A., and Daniel-Vedele, F. (2003). Quantitative trait loci analysis of water and anion contents in interaction with nitrogen availability in Arabidopsis thaliana. Genetics 163, 711–722.

Lu, C., Han, M. H., Guevara-Garcia, A., and Fedoroff, N. V. (2002). Mitogen-activated protein kinase signaling in postgermination arrest of development by abscisic acid. Proc. Natl. Acad. Sci. USA 99, 15812–15817.

Maas, E. V. (1990). Crop salt tolerance. In ‘‘Agricultural Salinity Assessment and Management’’ (K. K. Tanji, ed.), pp. 262–304. Amer. Soc. Civil Eng., New York.

Maathuis, F. J. M., and Sanders, D. (1996). Mechanisms of potassium absorption by higher plant roots. Physiol. Plant. 96, 158–168.

Maathuis, F. J. M., Verlin, D., Smith, F. A., Sanders, D., Fernández, J. A., and Walker, N. A. (1996). The physiological relevance of Na+ -coupled K+ -transport. Plant Physiol. 112, 1609–1616.

Majee, M., Maitra, S., Dastidar, K. G., Pattnaik, S., Chatterjee, A., Hait, N. C., Das, K. P., and An Majumder, A. L. (2004). A novel salt-tolerant L-myo-inositol-1-phosphate synthase from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice, molecular cloning, bacterial overexpression, characterization, and functional introgression into tobacco conferring salt tolerance phenotype. J. Biol. Chem. 279, 28539–28552.

Marin, K., Suzuki, I., Yamaguchi, K., Ribbeck, K., Yamamoto, H., Kanesaki, Y., Hagemann, M., and Murata, N. (2003). Identification of histidine kinases that act as sensors in the perception of salt stress in Synechocystis sp. PCC 6803. Proc. Natl. Acad. Sci. USA 100, 9061–9066.

Mäser, P., Gierth, M., and Schroeder, J. I. (2002). Molecular mechanisms of potassium and sodium uptake in plants. Plant Soil 247, 43–54.

Matsumoto, T. K., Ellsmore, A. J., Cessna, S. G., Low, P. S., Pardo, J. M., Bressan, R. A., and Hasegawa, P. M. (2002). An osmotically induced cytosolic Ca2+ transient activates calcineurin signaling to mediate ion homeostasis and salt tolerance of Saccharomyces cerevisiae. J. Biol. Chem. 277, 33075–33080.

Mazel, A., Leshem, Y., Tiwari, B. S., and Levine, A. (2004). Induction of salt and osmotic stress tolerance by overexpression of an intracellular vesicle trafficking protein AtRab7 (AtRabG3e). Plant Physiol. 134, 118–128.

Mckersie, B. D., Bowley, S. R., Harjanto, E., and Leprince, O. (1996). Water-deficit tolerance and field performance of transgenic alfalfa overexpressing superoxide dismutase. Plant Physiol. 111, 1177–1181.

Mikolajczyk, M., Awotunde, O. S., Muszyska, G., Klessig, D. F., and Dobrowolska, G. (2000). Osmotic stress induces rapid activation of a salicylic acid-induced protein kinase and a homolog of protein kinase ASK1 in tobacco cells. Plant Cell 12, 165–178.

Mittova, V., Theodoulou, F. L., Kiddle, G., Gomez, L., Volokita, M., Tal, M., Foyer, C. H., and Guy, M. (2003). Coordinate induction of glutathione biosynthesis and glutathione-metabolizing enzymes is correlated with salt tolerance in tomato. FEBS Lett. 554, 417–421.

Mukhopadhyay, A., Vij, S., and Tyagi, A. K. (2004). Overexpression of a zinc-finger protein gene from rice confers tolerance to cold, dehydration, and salt stress in transgenic tobacco. Proc. Natl. Acad. Sci. USA 101, 6309–6314.

Munns, R. (1993). Physiological processes limiting plant growth in saline soils, some dogmas and hypotheses. Plant Cell Environ. 16, 15–24.

Munns, R. (2002). Comparative physiology of salt and water stress. Plant Cell Environ. 25, 239–250.

Munns, R., Husain, S., Rivelli, A. R., James, R. A., Condon, A. G., Lindsay, M. P., Lagudah, E. S., Schachtman, D., and Hare, R. A. (2002). Avenues for increasing salt tolerance of crops, and the role of physiologically-based selection traits. Plant Soil 247, 93–105.

Nagaoka, S., and Takano, T. (2003). Salt tolerance-related protein STO binds to a Myb transcription factor homologue and confers salt tolerance in Arabidopsis. J. Exp. Bot. 54, 2231–2237.

Nakayama, H., Yoshida, K., Ono, H., Murooka, Y., and Shinmyo, A. (2000). Ectoine, the compatible solute of Halomonas elongata, confers hyperosmotic tolerance in cultured tobacco cells. Plant Physiol. 122, 1239–1247.

Nakayama, H., Yoshida, K., and Shinmyo, A. (2004). Yeast plasma membrane Ena1p ATPase alters alkali-cation homeostasis and confers increased salt tolerance in tobacco cultured cells. Biotechnol. Bioeng. 85, 776–789.

Nanjo, T., Kobayashi, M., Yoshiba, Y., Kakubari, Y., Yamaguchi-Shinozaki, K., and Shinozaki, K. (1999). Antisense suppression of praline degradation improves tolerance to freezing and salinity in Arabidopsis thaliana. FEBS Lett. 461, 205–210.

Niu, X., Bressan, R. A., Hasegawa, P. M., and Pardo, J. M. (1995). Ion homeostasis in NaCl stress environments. Plant Physiol. 109, 735–742.

Nomura, M., Ishitani, M., Takabe, T., Rai, A. K., and Takabe, T. (1995). Synechococcus sp. PCC7942 transformed with Escherichia coli bet genes produces glycine betaine from choline and acquires resistance to salt stress. Plant Physiol. 107, 703–708.

Nordin, K., Heino, P., and Palva, E. T. (1991). Separate signal pathways regulate the expression of a low-temperature-induced gene in Arabidopsis thaliana (L.) Heynh. Plant Mol. Biol. 16, 1061–1071.

Norlyn, J. D. (1979). Breeding salt-tolerant crop plants. Basic Life Sci. 14, 293–309.

Novillo, F., Alonso, J. M., Ecker, J. R., and Salinas, J. (2004). CBF2/DREB1C is a negative regulator of CBF1/DREB1B and CBF3/DREB1A expression and plays a central role in stress tolerance in Arabidopsis. Proc. Natl. Acad. Sci. USA 101, 3985–3990.

Nublat, A., Desplans, J., Casse, F., and Berthomieu, P. (2001). sas1, an Arabidopsis mutant overaccumulating sodium in the shoot, shows deficiency in the control of the root radial transport of sodium. Plant Cell 13, 125–137.

O’Leary, J. W., Glenn, E. P., and Watson, M. C. (1985). Agricultural production of halophytes irrigated with seawater. Plant Soil 89, 311–321.

Pardo, J. M., and Quintero, F. J. (2002). Plants and sodium ions, keeping company with the enemy. Genome Biol. 3, 1017.1–1017.4.

Pardo, J. M., Reddy, M. P., Yang, S., Maggio, A., Huh, G.-H., Matsumoto, T., Coca, M. A., Paino- D’Urzo, M., Koiwa, H., Yun, D.-J., Watad, A. A., Bressan, R. A., et al. (1998). Stress signaling through Ca2+ /calmodulin-dependent protein phosphatase calcineurin mediates salt adaptation in plants. Proc. Natl. Acad. Sci. USA 95, 9681–9686.

Park, J. M., Park, C. J., Lee, S. B., Ham, B. K., Shin, R., and Paek, K. H. (2001). Overexpression of the tobacco Tsi1 gene encoding an EREBP/AP2-type transcription factor enhances resistance against pathogen attack and osmotic stress in tobacco. Plant Cell 13, 1035–1046.

Perruc, E., Charpenteau, M., Ramirez, B. C., Jauneau, A., Galaud, J. P., Ranjeva, R., and Ranty, B. (2004). A novel calmodulin-binding protein functions as a negative regulator of osmotic stress tolerance in Arabidopsis thaliana seedlings. Plant J. 38, 410–420.

Pilot, G., Gaymard, F., Mouline, K., Cherel, I., and Sentenac, H. (2003). Regulated expression of Arabidopsis shaker K+ channel genes involved in K+ uptake and distribution in the plant. Plant Mol. Biol. 51, 773–787.

Price, A. H., Cairns, J. E., Horton, P., Jones, H. G., and Griffiths, H. (2002). Linking drought-resistance mechanisms to drought avoidance in upland rice using a QTL approach, progress and new opportunities to integrate stomatal and mesophyll responses. J. Exp. Bot. 53, 989–1004.

Provart, N. J., and Mccourt, P. (2004). Systems approaches to understanding cell signaling and gene regulation. Curr. Opin. Plant Biol. 7, 605–609.

Qi, Z., and Spalding, E. P. (2004). Protection of plasma membrane K+ transport by the salt overly sensitive1 Na+ -H+ antiporter during salinity stress. Plant Physiol. 136, 2548–2555.

Qiu, Q.-S., Guo, Y., Dietrich, M. A., Schumaker, K. S., and Zhu, J.-K. (2002). Regulation of sos1, a plasma membrane Na+ /H+ exchanger in Arabidopsis thaliana, by sos2 and sos3. Proc. Natl. Acad. Sci. USA 99, 8436–8441.

Qiu, Q.-S., Barkla, B. J., Vera-Estrella, R., Zhu, J.-K., and Schumaker, K. S. (2003). Na+ /H+ exchange activity in the plasma membrane of Arabidopsis. Plant Physiol. 132, 1041–1052.

Quesada, V., Garcia-Martinez, S., Piqueras, P., Ponce, M. R., and Micol, J. L. (2002). Genetic architecture of NaCl tolerance in Arabidopsis. Plant Physiol. 130, 951–963.

Quintero, F. J., Garciadeblas, B., and Rodriguez-Navarro, A. (1996). The SAL1 gene of Arabidopsis, encoding an enzyme with 30(20),50-bisphosphate nucleotidase and inositol polyphosphate 1-phosphatase activities, increases salt tolerance in yeast. Plant Cell 8, 529–537.

Quintero, F. J., Ohta, M., Shi, H., Zhu, J.-K., and Pardo, J. M. (2002). Reconstitution in yeast of the Arabidopsis sos signaling pathway for Na+ homeostasis. Proc. Natl. Acad. Sci. USA 99, 9061–9066.

Rains, D. W., and Epstein, E. (1965). Transport of sodium in plant tissue. Science 148, 1611.

Rains, D. W., and Epstein, E. (1967). Sodium absorption by barley roots: Role of the dual mechanisms of alkali cation transport. Plant Physiol. 42, 314–318.

Ramage, R. (1980). Genetic methods to breed salt tolerance in plants. In ‘‘Genetic Engineering of Osmoregulation Impact on Plant Productivity for Food, Chemicals and Energy’’ (D. Rains, R. Valentine, and A. Hollaender, eds.), pp. 311–318. Plenum Press, New York.

Ribaut, J.-M., and Hoisington, D. (1998). Marker-assisted selection, new tools and strategies. Trends Plant Sci. 3, 236–239.

Rigas, S., Debrosses, G., Haralampidis, K., Vicente-Agullo, F., Feldmann, K. A., Grabov, A., Dolan, L., and Hatzopoulos, P. (2001). TRH1 encodes a potassium transporter required for tip growth in Arabidopsis root hairs. Plant Cell 13, 139–151.

Roberts, S. K., and Tester, M. (1997). A patch clamp study of Na þ transport in maize roots. J. Exp. Bot. 48, 431–440.

Romero, C., Belles, J. M., Vaya, J. L., Serrano, R., and Culian˜ez-Maciá , F. A. (1997). Expression of the yeast trehalose-6-phosphate synthase gene in transgenic tobacco plants, pleiotropic phenotypes include drought tolerance. Planta 201, 293–297.

Rontein, D., Basset, G., and Hanson, A. D. (2002). Metabolic engineering of osmoprotectant accumulation in plants. Metab. Eng. 4, 49–56.

Ros, R., Montesinos, C., Rimon, A., Padan, E., and Serrano, R. (1998). Altered Na+ and Li+ homeostasis in Saccharoyces cerevisiae expressing the bacterial cation antiporter NhaA. J. Bacteriol. 180, 3131–3136.

Roxas, V. R., Smigh, R. K., Jr., Allen, E. R., and Allen, R. D. (1997). Overexpression of glutathione-Stransferase/ glutathione peroxidase enhances the growth of transgenic tobacco seedlings during stress. Nat. Biotechnol. 15, 988–991.

Rubio, F., Gassmann, W., and Schroeder, J. I. (1995). Sodium-driven potassium uptake by the plant transporter HKT1 and mutations conferring salt tolerance. Science 270, 1660–1663.

Rubio, F., Schwarz, M., Gassmann, W., and Schroeder, J. I. (1999). Genetic selection of mutations in the high affinity K þ transporter HKT1 that defines functions of a loop site for reduced Na+ permeability and increased Na þ tolerance. J. Biol. Chem. 274, 6839–6847.

Rus, A., Yokoi, S., Sharkhuu, A., Reddy, M., Lee, B.-H., Matsumoto, T. K., Koiwa, H., Zhu, J.-K., Bressan, R. A., and Hasegawa, P. M. (2001). AtHK1 is a salt tolerance determinant that controls Na+ entry into plant roots. Proc. Natl. Acad. Sci. USA 98, 14150–14155.

Rus, A., Lee, B.-H., Munoz-Mayor, A., Sharkhuu, A., Miura, K., Zhu, J.-K., Bressan, R. A., and Hasegawa, P. M. (2004). AtHKT1 facilitates Na+ homeostasis and K+ nutrition in planta. Plant Physiol. 136, 2500–2511.

Rush, P. W., and Epstein, E. (1981). Breeding and selection for salt tolerance by the incorporation of wild germplasm into a domestic tomato. J. Am. Soc. Hort. Sci. 106, 699–704.

Saijo, Y., Hata, S., Kyozuka, J., Shimamoto, K., and Izui, K. (2000). Over-expression of a single Ca2+ -dependent protein kinase confers both cold and salt/drought tolerance on rice plants. Plant J. 23, 319–327.

Sakamoto, H., Maruyama, K., Sakuma, Y., Meshi, T., Iwabuchi, M., Shinozaki, K., and Yamaguchi- Shinozaki, K. (2004). Arabidopsis Cys2/His2-type zinc-finger proteins function as transcription repressors under drought, cold, and high-salinity stress conditions. Plant Physiol. 136, 2734–2746.

Schachtman, D. P. (2000). Molecular insights into the structure and function of plant K+ transport mechanisms. Biochim. Biophys. Acta 1465, 127–139.

Seki, M., Ishida, J., Narusaka, M., Fujita, M., Nanjo, T., Umezawa, T., Kamiya, A., Nakajima, M., Enju, A., and Sakurai, T. (2002). Monitoring the expression pattern of around 7,000 Arabidopsis genes under ABA treatments using a full-length cDNA microarray. Funct. Integr. Genom. 2, 282–291.

Seo, M., Koiwai, H., Akaba, S., Komano, T., Oritani, T., Kamiya, Y., and Koshiba, T. (2000). Abscisic aldehyde oxidase in leaves of Arabidopsis thaliana. Plant J. 23, 481–488.

Serrano, R. (1996). Salt tolerance in plants and microorganisms, toxicity targets and defense responses. Int. Rev. Cytol. 165, 1–52.

Serrano, R., and Rodriguez-Navarro, P. L. (2002). Plants, genes and ions. Workshop on the molecular basis of ionic homeostasis and salt tolerance in plants. EMBO Rep. 3, 116–119.

Serrano, R., Culian˜z-Macia´ , A., and Moreno, V. (1999). Genetic engineering of salt and drought tolerance with yeast regulatory genes. Sci. Hortic. 78, 261–269.

Shen, B., Jensen, R. G., and Bohnert, H. J. (1997). Mannitol protects against oxidation by hydroxyl radicals. Plant Physiol. 115, 527–532.

Sheveleva, E., Chmara, W., Bohnert, H. J., and Jensen, R. G. (1997). Increased salt and drought tolerance by D-ononitol production in transgenic Nicotiana tabacum L. Plant Physiol. 115, 1211–1219.

Sheveleva, E., Jensen, R. G., and Bohnert, H. J. (2000). Disturbance in the allocation of carbohydrates to regenerative organs in transgenic Nicotiana tabacum L. J. Exp. Bot. 51, 115–122.

Shi, H., and Zhu, J.-K. (2002). Regulation of expression of the vacuolar Na þ /H þ antiporter gene AtNHX1 by salt stress and ABA. Plant Mol. Biol. 50, 543–550.

Shi, H., Ishitani, M., Kim, C., and Zhu, J.-K. (2000). The Arabidopsis thaliana salt tolerance gene sos1 encodes a putative Na+ /H+ antiporter. Proc. Natl. Acad. Sci. USA 97, 6896–6901.

Shi, H., Lee, B.-H., Wu, S.-J., and Zhu, J.-K (2003). Overexpression of a plasma membrane Na+ /H+ antiporter gene improves salt tolerance in Arabidopsis thaliana. Nat. Biotechnol. 21, 81–85.

Shinozaki, K., and Yamaguchi-Shinozaki, K. (1999). Molecular responses to drought stress.

In ‘‘Molecular Responses to Cold, Drought, Heat and Salt Stress in Higher Plants’’ (K. Shinozaki and K. Shinozaki-Yamaguchi, eds.), pp. 11–28. R. G. Landes, Austin, Texas.

Shinozaki, K., Yamaguchi-Shinozaki, K., and Seki, M. (2003). Regulatory network of gene expression in the drought and cold stress responses. Curr. Opin. Plant Biol. 6, 410–417.

Singla-Pareek, S. L., Reddy, M. K., and Sopory, S. K. (2003). Genetic engineering of the glyoxalase pathway in tobacco leads to enhanced salinity tolerance. Proc. Natl. Acad. Sci. USA 100, 14672–14677.

Sondergaard, T. E., Schulz, A., and Palmgren, M. G. (2004). Energization of transport processes in plants. Roles of the plasma membrane H+ -ATPase. Plant Physiol. 136, 2475–2482.

Su, H., Golldack, D., Katsuhara, M., Zhao, C., and Bohnert, H. J. (2001). Expression and stressdependent induction of potassium channel transcripts in the common ice plant. Plant Mol. Biol. 51, 773–787.

Su, H., Golldack, D., Zhao, C., and Bohnert, H. J. (2002). The expression of HAK-type K(þ) transporters is regulated in response to salinity stress in common ice plant. Plant Physiol. 129, 1482–1493.

Su, H., Balderas, E., Vera-Estrella, R., Golldack, D., Quigley, F., Zhao, C., Pantoya, O., and Bohnert, H. J. (2003). Expression of the cation transporter McHKT1 in a halophyte. Plant Mol. Biol. 52, 967–980.

Sulpice, R., Tsukaya, H., Nonaka, H., Mustardy, L., Chen, T. H., and Murata, N. (2003). Enhanced formation of flowers in salt-stressed Arabidopsis after genetic engineering of the synthesis of glycine betaine. Plant J. 36, 165–176.

Suzuki, I., Los, D. A., Kanesaki, Y., Mikami, K., and Murata, N. (2000). The pathway for perception and transduction of low-temperature signals in Synechocystis. EMBO J. 19, 1327–1334.

Taji, T., Seki, M., Satou, M., Sakurai, T., Kobayashi, M., Ishiyama, K., Narusaka, Y., Narusaka, M., Zhu, J. K., and Shinozaki, K. (2004). Comparative genomics in salt tolerance between Arabidopsis and Arabidopsis-related halophyte salt cress using Arabidopsis microarray. Plant Physiol. 135, 1697–1709.

Talke, I. N., Blaudez, D., Maathuis, F. J. M., and Sanders, D. (2003). CNGCs, prime targets of plant cyclic nucleotide signaling? Trends Plant Sci. 8, 286–293.

Tani, H., Chen, X., Nurmberg, P., Grant, J. J., Santamaria, M., Chini, A., Gilroy, E., Birch, P. R., and Loake, G. J. (2004). Activation tagging in plants, a tool for gene discovery. Funct. Integr. Genom. 4, 258–266.

Tarczynski, M., Jensen, R. G., and Bohnert, H. J. (1993). Stress protection of transgenic tobacco by production of the osmolyte mannitol. Science 259, 508–510.

Teige, M., Scheikl, E., Eulgem, T., Doczi, R., Ichimura, K., Shinozaki, K., Dangl, J. L., and Hirt, H. (2004). The MKK2 pathway mediates cold and salt stress signaling in Arabidopsis. Mol. Cell. 15, 141–152.

Tester, M., and Davenport, R. (2003). Na+ tolerance and Na+ transport in higher plants. Ann. Bot. (Lond.) 91, 503–527.

Trewavas, A. J. (2001). The population/biodiversity paradox. Agricultural efficiency to save wilderness. Plant Physiol. 125, 174–179.

Tuberosa, R., Salvi, S., Sanguineti, M. C., Landi, P., MacCaferri, M., and Conti, S. (2002). Mapping QTLs regulating morpho-physiological traits and yield: Case studies, shortcomings and perspectives in drought-stressed maize. Ann. Bot. (Lond.) 89, 941–963.

Urano, K., Yoshiba, Y., Nanjo, T., Ito, T., Yamaguchi-Shinozaki, K., and Shinozaki, K. (2004). Arabidopsis stress-inducible gene for arginine decarboxylase AtADC2 is required for accumulation of putrescine in salt tolerance. Biochem. Biophys. Res. Commun. 313, 369–375.

Urao, T., Yakubov, B., Satoh, R., Yamaguchi-Shinozaki, K., Seki, M., Hirayama, T., and Shinozaki, K. (1999). A transmembrane hybrid-type histidine kinase in Arabidopsis functions as an osmosensor. Plant Cell 11, 1743–1754.

Van Camp, W. (2005). Yield enhancement genes: Seeds for growth. Curr. Opin. Biotechnol. 16, 147–153.

Van Camp, W., Capiau, K., Van Montagu, M., Inze, D., and Slooten, L. (1996). Enhancement of oxidative stress tolerance in transgenic tobacco plants overproducing Fe-superoxide dismutase in chloroplasts. Plant Physiol. 112, 1703–1714.

Veena, Reddy, V. S., and Sopory, S. K. (1999). Glyoxalase I from Brassica juncea, molecular cloning, regulation and its over-expression confer tolerance in transgenic tobacco under stress. Plant J. 17, 385–395.

Vera-Estrella, R., Barkla, B. J., Bohnert, H. J., and Pantoja, O. (1999). Salt-stress in Mesembryanthemum crystallinum suspensions activates adaptive mechanisms similar to those observed in the whole plant. Planta 207, 426–435.

Verslues, P. E., and Bray, E. A. (2004). LWR1 and LWR2 are required for osmoregulation and osmotic adjustment in Arabidopsis. Plant Physiol. 136, 2831–2842.

Villalobos, M. A., Bartels, D., and Iturriaga, G. (2004). Stress tolerance and glucose insensitive phenotypes in Arabidopsis overexpressing the CpMYB10 transcription factor gene. Plant Physiol. 135, 309–324.

Vitart, V., Baxter, I., Doerner, P., and Harper, J. F. (2001). Evidence for a role in growth and salt resistance of a plasma membrane H+ -ATPase in the root endodermis. Plant J. 27, 191–201.

Wada, Y., Miyamoto, K., Kusano, T., and Sano, H. (2004). Association between up-regulation of stressresponsive genes and hypomethylation of genomic DNA in tobacco plants. Mol. Genet. Genom. 271, 658–666.

Waditee, R., Hibino, T., Nakamura, T., Incharoensakdi, A., and Takabe, T. (2002). Overexpression of a Na+ /H+ antiporter confers salt tolerance on a freshwater cyanobacterium, making it capable of growth in sea water. Proc. Natl. Acad. Sci. USA 99, 4109–4114.

Wang, W., Vinocur, B., and Altman, A. (2003). Plant responses to drought, salinity and extreme temperatures, towards genetic engineering for stress tolerance. Planta 218, 1–14.

Ward, J. M., Hirschi, K. D., and Sze, H. (2003). Plants pass the salt. Trends Plant Sci. 8, 200–201.

Warren, G., Mckown, R., Martin, A. L., and Teutonico, V. (1996). Isolation of mutations affecting the development of freezing tolerance in Arabidopsis thaliana (L.) Heynh. Plant Physiol. 111, 1011–1019.

Werner, J. E., and Finkelstein, R. R. (1995). Arabidopsis mutants with reduced response to NaCl and osmotic stress. Physiol. Plant. 93, 659–666.

Winicov, I., and Bastola, D. R. (1999). Transgenic overexpression of the transcription factor A1fin1 enhances expression of the endogenous MsPRP2 gene in alfalfa and improves salinity tolerance of the plants. Plant Physiol. 120, 473–480.

Wu, C. A., Yang, G. D., Meng, Q. W., and Zheng, C. C. (2004). The cotton GhNHX1 gene encoding a novel putative tonoplast Na(þ)/H(þ) antiporter plays an important role in salt stress. Plant Cell Physiol. 45, 600–607.

Xiong, L., and Zhu, J. K. (2003). Regulation of abscisic acid biosynthesis. Plant Physiol. 133, 29–36.

Xiong, L., Gong, Z., Rock, C. D., Subramanian, S., Guo, Y., Xu, W., Galbraith, D., and Zhu, J.-K. (2001a). Modulation of abscisic acid signal transduction and biosynthesis by an Sm-like protein in Arabidopsis. Dev. Cell 1, 771–781.

Xiong, L., Ishitani, M., Lee, H., and Zhu, J. K. (2001b). The Arabidopsis LOS5/ABA3 locus encodes a molybdenum cofactor sulfurase and modulates cold stress- and osmotic stress-responsive gene expression. Plant Cell 13, 2063–2083.

Xiong, L., Lee, H., Ishitani, M., Tanaka, Y., Stevenson, B., Koiwa, H., Bressan, R. A., Hasegawa, P. M., and Zhu, J.-K. (2002a). Repression of stress-responsive genes by FIERY2, a novel transcriptional regulator in Arabidopsis. Proc. Natl. Acad. Sci. USA 99, 10899–10904.

Xiong, L., Schumaker, K. S., and Zhu, J.-K. (2002b). Cell signaling during cold, drought, and salt stress. Plant Cell 14, S165–S183.

Yale, J., and Bohnert, H. J. (2001). Transcript expression in Saccharomyces cerevisiae at high salinity. J. Biol. Chem. 276, 15996–16007.

Yokoi, S., Quintero, F. J., Cubero, B., Ruiz, M. T., Bressan, R. A., Hasegawa, P. M., and Pardo, J. M. (2002). Differential expression and function of Arabidopsis thaliana NHX Na+ /H+ antiporters in the salt stress response. Plant J. 30, 529–539.

Yu, J., Hu, S., Wang, J., Wong, G. K., Li, S., Liu, B., Deng, Y., Dai, L., Zhou, Y., Zhang, X., Cao, M., Liu, J., et al. (2002). A draft sequence of the rice genome (Oryza sativa L. ssp. indica). Science 296, 79–92.

Zhang, H. X., and Blumwald, E. (2001). Transgenic salt-tolerant tomato plants accumulate salt in foliage but not in fruit. Nat. Biotech. 19, 765–768.

Zhang, H. X., Hodson, J. N., Williams, J. P., and Blumwald, E. (2001). Engineering salt-tolerant Brassica plants, characterization of yield and seed oil quality in transgenic plants with increased sodium accumulation. Proc. Natl. Acad. Sci. USA 98, 12832–12836.

Zhang, H., Huang, Z., Xie, B., Chen, Q., Tian, X., Zhang, X., Zhang, H., Lu, X., Huang, D., and Huang, R. (2004). The ethylene-, jasmonate-, abscisic acid- and NaCl-responsive tomato transcription factor JERF1 modulates expression of GCC box-containing genes and salt tolerance in tobacco. Planta 220, 262–270.

Zhao, Z., Chen, G., and Zhang, C. (2001). Interaction between reactive oxygen species and nitric oxide in drought-induced abscisic acid synthesis in root tips of wheat seedlings. Aust. J. Plant Physiol. 28, 1055–1061.

Zhifang, G., and Loescher, W. H. (2003). Expression of a celery mannose 6-phosphate reductase in Arabidopsis thaliana enhances salt tolerance and induces biosynthesis of both mannitol and a glucosyl-mannitol dimmer. Plant Cell Environ. 26, 275–283.

Zhu, J.-K. (2000). Genetic analysis of plant salt tolerance using Arabidopsis. Plant Physiol. 124, 941–948.

Zhu, J.-K. (2001). Plant salt tolerance. Trends Plant Sci. 6, 66–71.

Zhu, J.-K. (2002). Salt and drought stress signal transduction in plants. Annu. Rev. Plant Biol. 53, 247–273.

Zhu, J.-K. (2003). Regulation of ion homeostasis under salt stress. Curr. Opin. Plant Biol. 6, 441–445.