Ascorbate-glutathione cycle confers salt tolerance in Egyptian lentil cultivars

In order to investigate the salt tolerance mechanism in Egyptian lentils, five cultivars were grown under different salinity levels. The results indicated that Giza 9 is salt-tolerant, while Giza 4 is a salt-sensitive lentil cultivar, as Giza 9 showed the highest germination percentage and relative water content, the lowest decline in root and shoot length, and the highest proline content. Relative gene expression of ADH, CYS3, APX, SOD, and GR was significantly upregulated in Giza 9 roots after 24 h of high salt treatment (250 mM), while CAT transcripts level was non-significantly reduced (0.5-fold) relative to control. However, in Giza 4, only CAT gene was significantly upregulated in both root (2.3-fold) and shoot (8.5-fold) tissues. Investigation of ascorbate-glutathione enzymatic activities revealed significantly higher ascorbate peroxidase and glutathione reductase activities in Giza 9 roots compared to its shoots. Moreover, endogenous reduced glutathione (GSH) content as well as reduced ascorbate content were significantly high in the roots of Giza 9 compared to Giza 4. These results strongly indicate the involvement of ascorbate-glutathione cycle in the tolerance mechanism of Giza 9. Furthermore, exogenous application of 350 μM of GSH assisted Giza 4 seedlings to tolerate salinity stress. As far as we know, this is the first work reporting the involvement of ascorbate-glutathione cycle in salt tolerance of lentil.