Overexpression of a PLDα1 gene from Setaria italica enhances the sensitivity of Arabidopsis to abscisic acid and improves its drought tolerance

Phospholipase D (PLD) plays an important role in various physiological processes in plants, including drought tolerance. Here, we report the cloning and characterization of the full-length cDNA of PLD alpha 1 from foxtail millet, which is a cereal crop with high water use efficiency. The expression pattern of the SiPLD alpha 1 gene in foxtail millet revealed that it is up-regulated under dehydration, ABA and NaCl treatments. Heterologous overexpression of SiPLD alpha 1 in Arabidopsis can significantly enhance their sensitivity to ABA, NaCl and mannitol during post-germination growth. Under water deprivation, overexpression of SiPLD alpha 1 in Arabidopsis resulted in significantly enhanced tolerance to drought stress, displaying higher biomass and RWC, lower ion leakage and higher survival percentages than the wild type. Further analysis indicated that transgenic plants showed increased transcription of the stress-related genes, RD29A, RD29B, RAB18 and RD22, and the ABA-related genes, ABI1 and NCED3 under dehydration conditions. These results demonstrate that SiPLD alpha 1 is involved in plant stress signal transduction, especially in the ABA signaling pathway. Moreover, no obvious adverse effects on growth and development in the 35S::SiPLD alpha 1 transgenic plants implied that SiPLD alpha 1 is a good candidate gene for improving crop drought tolerance.