The pyramid of transgenes TsVP and BetA effectively enhances the drought tolerance of maize plants

P>Stress resistance has repeatedly been enhanced in plants by the transfer of a single gene using genetic engineering. However, further enhancement of resistance to abiotic stress is still necessary. In our research, maize plants that were transgenic for both betA (encoding choline dehydrogenase from Escherichia coli) and TsVP (encoding V-H+-PPase from Thellungiella halophila) were produced by cross-pollination. The existence of the transgenes in the pyramided plants was demonstrated by PCR and Southern blotting. The stable expression of transgenes was confirmed by real-time RT-PCR (reverse transcription polymerase chain reaction) analysis. An examination of the drought resistance characteristics demonstrated that the pyramided transgenic plants had higher glycinebetaine contents and H+-PPase activity compared with the parental lines, which had either betA or TsVP, and contained higher relative water content (RWC), greater solute accumulation and lower cell damage under drought stress treatment. The pyramided plants grew more vigorously with less growth retardation, shorter anthesis-silking interval and higher yields than their parental lines and the wild-type. We concluded that co-expression of the two genes involved in different metabolism pathways in pyramided transgenic maize helped to improve the drought resistance over their parental lines that contained either single transgene. Our study suggests that the co-expression of multiple, effective genes in transgenic plants could effectively enhance the resistance to abiotic stress and provide a feasible approach for obtaining maize plants with improved drought resistance.