Effect of salt stress on the expression of NHX-type ion transporters in Medicago intertexta and Melilotus indicus plants
2007
Zahran, Hamdi H. | Marín-Manzano, M Carmen | Sánchez-Raya, A Juan | Bedmar, Eulogio J. | Venema, Kees | Rodríguez-Rosales, M Pilar
Medicago intertexta and Melilotus indicus, two wild leguminous herbs with different tolerance to salinity were investigated for NaCl-induced changes in the expression level of some Na⁺ transporters. M. indicus plants grew well at NaCl concentration from 0 to 400 mM, whereas growth of M. intertexta plants was severely inhibited at NaCl concentrations higher than 100 mM. In M. intertexta, increasing NaCl in the growth media caused a strong increase in Na⁺ content concomitant with a decrease in K⁺ content in leaves and, above all, roots. In comparison, M. indicus plants cultivated in the presence of NaCl accumulated much less Na⁺ in leaves and roots and no differences in K⁺ content among plants grown in nutrient solution containing 100-400 mM NaCl were detected. The expression levels of four genes coding for NHX-type Na⁺/H⁺ antiporters in the above two wild legumes were studied in plants cultivated under the different NaCl concentrations. Expression levels of the genes were higher in M. intertexta as compared with M. indicus plants. In M. intertexta, salt treatments increased MtNHX1, MtNHX3 and MtNHX4 transcript levels in leaves and roots. However, in M. indicus NaCl treatments only induced the expression of MtNHX1 in roots. Our data suggest that two different mechanisms, Na⁺ avoidance or accumulation into cellular compartments, are developed by the two wild legumes to cope with salt stress, and that expression of NHX antiporters is linked to the accumulator phenotype.
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