Heterologous expression of the TsVP gene improves the drought resistance of maize

In this study, it was shown that the TsVP gene [vacuolar H+-pyrophosphatase (V-H+-PPase) gene from a dicotyledonous halophyte Thellungiella halophila] could be transferred into the monocotyledonous crop maize (Zea mays L.), and that the heterologous expression of the transgene improved the drought resistance of transgenic plants. Polymerase chain reaction amplification and Southern blotting confirmed the existence of the foreign gene in transformed plants and their progeny. Expression differences of the TsVP gene in different transgenic lines were monitored by reverse transcriptase-polymerase chain reaction. The measurement of isolated vacuolar membrane vesicles from the TsVP transgenic and wild-type (WT) plants demonstrated that the transgenic plants had higher V-H+-PPase activity, and the performance of maize-expressed TsVP in response to osmotic/drought stress was better in lines with higher V-H+-PPase activity. Transgenic plants showed a higher percentage of seed germination, better developed root systems and greater biomass, greater solute accumulation and less cell membrane damage relative to WT plants under osmotic stress. After drought stress treatment, transgenic plants showed less growth retardation and shorter anthesis-silking interval, and produced much larger grain yields, than WT plants. It was concluded that the high V-H+-PPase activity of transgenic maize improved the drought resistance of plants. This report provides a feasible approach to increase monocotyledonous crop yields under conditions of soil water deficit by the heterologous expression of TsVP.