Interaction of osmotic and temperature stress on transgenic soybean

The triphenyltetrazolium chloride (TTC) assay is based on the ability of viable cells to metabolically reduce tetrazolium salts to formazan. It was used as a method to screen the viability differences of soybean plants transformed with a P5CR gene in antisense direction controlled by an Inducible heat shock promoter (IHSP). Differences were detected between the transgenics and the control plants using this method. The transgenics exhibited a sensitive reaction in that formazan production was reduced following an osmotic stress treatment. The control plants however exhibited a tolerant reaction in that formazan production was highest during stress treatment. The efficiency of protein synthesis in the transgenic plants was lower than in the control plants when the inducible heat shock promoter was activated. This indicated that underexpression of the P5CR gene resulted in declined protein synthesis due to proline shortage. The transgenics had a lower seed production than the control plants indicating that the antisense P5CR gene also influenced seed production negatively. The screening methods showed that the control plants were the most viable of the plants tested. The decrease in the proline level due to the activated antisense P5CR gene yielded plants that are directly or indirectly more sensitive to osmotic stress. It appears that the antisense transgenics were not able to withstand the osmotic stress due to the decline in proline synthesis. These findings indicate that proline plays an adaptive role during osmotic stress in soybean plants.