Osmotolerance and growth stimulation of transgenic tobacco cells accumulating free proline by silencing proline dehydrogenase expression with double‐stranded RNA interference technique

Abstract

Many higher plants accumulate free proline (Pro) to counteract osmotic stress. To examine the role of free Pro in salt resistance, we suppressed the tobacco Pro dehydrogenase (NtProDH) gene using a double‐stranded RNA interference technique in tobacco Bright Yellow 2 cells. Northern blot analysis showed reduced levels of the NtProDH transcripts in the transgenic line. The free Pro level in transgenic cells was about 1.2‐ to 3.0‐fold, and the Pro dehydrogenase activity was about 4.9–32.2% of those in wild‐type (WT) cells. The transgenic cells had an appearance markedly different from that of WT cells. Microscopic analysis revealed that the transgenic tobacco cells were mostly barrel shaped as in a filament, cylindrical and small. In synchronous cultures, transgenic cells showed more active cell division than WT cells. Hypersensitivity to exogenous Pro increased in the transgenic tobacco cells. The transgenic cells showed an increased osmotolerance, perhaps by free Pro accumulation.