Expression analysis of LeNHX1 gene in mycorrhizal tomato under salt stress

The plant growth, stem sap flow, Na(+) and Cl(-) content, and the expression of vacuolar Na(+)/H(+) antiporter gene (LeNHX1) in the leaves and roots of tomato under different NaCl stresses (0.5% and 1%) were studied to analyze the effect of arbuscular mycorrhizal fungi (AMF) on Na(+) and Cl(-) accumulation and ion exchange. The results showed that arbuscular mycorrhizal (AM) plant growth and stem sap flow increased and salt tolerance improved, whereas Na(+) and Cl(-) accumulated. Na(+) significantly decreased, and no significant decline was detected in Cl(-) content after AMF inoculation compared with the non-AM plants. The LeNHX1 gene expression was induced in the AM and non-AM plants by NaCl stress. However, AMF did not improve the LeNHX1 level, and low expression was observed in the AM tomato. Hence, the mechanism that reduced the Na(+) damage to tomato induced by AMF has little relation to LeNHX1, which can export Na(+) from the cytosol to the vacuole across the tonoplast.