Exogenous proline enhances the sensitivity of Tobacco BY-2 cells to arsenate

Arsenic causes physiological and structural disorders in plants. Proline is accumulated as a compatible solute in plants under various stress conditions and mitigates stresses. Here, we investigated the effects of exogenous proline on tobacco Bright Yellow-2 (BY-2) cultured cells under AsO4- stress. Arsenate did not inhibit BY-2 cell growth at 40 and 50 mu M but did it at 60 mu M. Proline at 0.5 to 10 mM did not affect the cell growth but delayed it at 20 mM. At 40 mu M AsO4-, neither 0.5 mM nor 1 mM proline affected the cell growth but 10 mM proline inhibited it. In the presence of AsO4-, 10 mM proline increased the number of Evans Blue-stained (dead) cells and decreased the number of total cells. Together, our results suggest that exogenous proline does not alleviate arsenate toxicity but enhances the sensitivity of BY-2 cells to arsenate.