Gene expression and physiological analysis of Atriplex halimus (L.) under salt stress

Atriplex halimus (L.) is a xero-halophyte shrub adapted to extreme drought and salinity stresses. Ability of local A. halimus to tolerate salinity stress was investigated. Two-month-old A. halimus plants were exposed to salt stress (0, 150, 300 and 600 mM NaCl) in properly aerated liquid medium. Differential gene expression of stressed plants was investigated using real-time PCR analysis. Furthermore, stress related physiological changes including photosynthetic efficiency, chlorophyll, carotenoid, free proline and MDA content were measured. Stressed plants showed increased expression of salt response genes compared to the control (intermediateassociated protein, acetohydroxy acid reductoisomerase, early-responsive to dehydration stress-related protein, ER-lumenal protein and membrane protein). Their expression was much higher at 150 mM than 300 mM stress level, indicating their specificity for low level salt stress. Photosynthetic activity was slightly decreased with both extended stress exposure and increased salt concentration, while total chlorophyll and proline increased under saline stress. The MDA level was significantly lower after 70 h compared to 30 h stress. Adaptation to salt stress is a complex trait governs by molecular changes expressed as physiological processes during plant development.