Overexpression of vacuolar H+-pyrophosphatase (H+-PPase) gene from Ammopiptanthus nanus enhances drought tolerance in maize

Maize is acutely vulnerable to water deficit. Due to the slow progress in conventional breeding, more beneficial genes should be transformed into maize for improvement of drought tolerance. In the present study, the vacuolar H+-pyrophosphatase (H+-PPase) gene (AnVP1) from Ammopiptanthus nanus was transformed into maize by Agrobacterium-mediated calli transformation. After identification of integration and ectopic expression of the AnVP1 gene by PCR amplification, DNA resequencing, reverse transcription PCR, real-time quantitative PCR, Western blotting and measurement of H+-PPase content, the transgenic lines were evaluated for their drought tolerance in greenhouse and field. The results of greenhouse phenotyping showed that the expression of AnVP1 decreased the negative effects of drought stress on transgenic maize with the improved performance, higher germination ratio, relative water content, biomass and more robust root system, slightly blasted leaves, lower electrolyte leakage and malondialdehyde content. The results of yield phenotyping showed that kernel yield of L1, L4 and L10 lines was significantly higher than WT under water deficit conditions. In conclusion, ectopic expression of the AnVP1 gene significantly enhanced drought tolerance of the transgenic maize, which is hopefully used for commercialized release after further safety assessment, because the expression of some endogenous genes was affected slightly.