Modulation of ion transporter genes of salt-stressed sorghum (Sorghum bicolor L. Moench) by foliar application of digitoxin.

Salinity poses a major threat to cereal crops such as sorghum. The foliar application of digitoxin at concentrations of 50, 100, and 200ppm was tested for its potential to alleviate salt stress in sorghum (Sorghum bicolor ) exposed to 200mM NaCl. Various growth parameters were analyzed, such as relative water content, malondialdehyde (MDA), osmoregulatory compunds (soluble carbohydrates and proline), ionic markers (Na+ and K+ levels in shoots and roots), and the expression of specific ion transporter genes including NHX , SOS1 , AKT1 , PPV , and PHA1 during the seedling stage. Digitoxin treatment significantly enhanced biochemical and ionic characteristics in salt-stressed plants by enhancing the membrane stability index and reducing MDA levels while boosting soluble carbohydrates, free amino acids, and proline. Real-time PCR showed that digitoxin application triggered the upregulation of genes promoting Na+ and K+ balance and reducing ion toxicity. This study underscores the potential role of digitoxin in improving salt tolerance through its influence on the regulation of ion transporter gene expression specific for K+ and Na+ ion transport and homeostasis. The effect of digitoxin on the ion transporters seems to be dose-dependent. The mechanism of digitoxin's effect on ion transporter gene expression of salt-stressed plants is discussed.