Salinity-induced changes in gene expression, ion homeostasis, and enzymatic antioxidants in contrasting wheat genotypes

Salinity is a major constraint on plant development and crop production for main crops such as wheat, which is the most important source of calories, especially at early stages of growth, including seed germination and seedling establishment. Salinity tolerance is a complex trait tailored by several mechanisms, including ion homeostasis, the activation of enzymatic antioxidants, and the alteration of ion transporter genes. Contrasting genotypes of wheat that differed in salinity tolerance were selected from a collection of 172 that were tested under salinity stress (175 mM NaCl) and the control (0 mM NaCl), with the aim of revealing the underlying mechanisms of salinity tolerance in the tolerant genotypes compared with the sensitive ones. These parameters, Na, K and P homeostasis; the presence of enzymatic antioxidants; and the expression profiles of the salinity-responsive ion transporter genes TaAVP1 and NHX1 were measured in one sensitive and six tolerant genotypes. The tolerant genotypes presented higher concentrations of Na ⁺ and K ⁺ and higher levels of all the enzymatic antioxidants than did the sensitive ones. The tolerant genotypes differentially expressed AVP1 and NHX1 , which were upregulated in Javelin 48 and Kandahar but downregulated in the tolerant genotype 1018d. These results indicate that the tolerant genotypes differentially expressed the ion transporter genes AVP1 and NHX1 . The tolerant genotype Kule presented the highest Na ⁺ content and the greatest increase in the levels of the antioxidant enzymes ascorbate peroxidase and glutathione reductase, with 9.20-fold and 2.32-fold changes, respectively, under salinity stress. In conclusion, the tolerant genotypes differed in their response to salinity stress and employed various mechanisms to tolerate salinity.