Over-Expression of AtEXPB2 Alleviates Salt Stress Damage in Transgenic Tobacco Plants

Expansin protein is a component of the cell wall that is generally accepted as a key regulator of the cell wall extension during plant growth and stress response. Expansins loosen the cell wall in a pH-dependent manner. To investigate the role of AtEXPB2, an Arabidopsis expansin gene, its mRNA expression level was analyzed in response to salt stress in overexpressed tobacco (Nicotiana tabacum L.). This over-expression of AtEXPB2 in transgenic lines was studied under salt stress in order to evaluate their resistance to salt stress conditions. In the findings of the current study, however, transgenic plants' cellular characteristics were probably altered because of the changes in some morphological traits like capsule seed weight, capsule weight, and root length; this alteration did not have any unfavorable effects on transgenic plant phenotypes. Transgenic lines were better than wild-type plant in terms of some morphological parameters, such as capsule number, capsule weight, total seed weight, and capsule seed number. In other words, seed yield was higher in transgenic lines than those in the control. Overexpression of AtEXPB2 conferred tolerance to salt stress by enhancing the activity of antioxidant enzymes, proline content, RWC, and chlorophyll, as well as reducing electrolyte leakage index (ELI). In addition, relative expression of AtEXPB2 and H+-ATPase gene increased in transgenic plants under salinity stress. Overall, these results confirmed the role of expansin proteins in plant stress tolerance.