Overexpression of the EuSIP5 Gene to Improve Drought Resistance in Tobacco

Soluble inorganic pyrophosphatase (s-PPase), a pyrophosphate hydrolase, is crucial for various physiological processes including plant growth and development, metabolic functions, and responses to abiotic stresses. However, research on s-PPase in woody plants is limited. To investigate the potential role of soluble inorganic pyrophosphatase in Eucommia ulmoides Oliver (E. ulmoides) in drought stress, the E. ulmoides soluble inorganic pyrophosphatase 5 (EuSIP5) cDNA sequence was amplified via RT-PCR. A bioinformatic analysis suggested that EuSIP5 may be an unstable amphipathic protein predominantly localized in the cytoplasm. In E. ulmoides, the highest expression of the EuSIP5 gene was detected in the leaves and pericarp of male plants from April to October, and in the leaves in July and September. Under drought conditions, the expression of EuSIP5 in E. ulmoides leaves was significantly greater than that in the control. An overexpression vector containing EuSIP5 was constructed and introduced into Nicotiana tabacum L. cv. Xanthi (N. tabacum L.). Compared with that in wild-type (WT) plants, wilting in N. tabacum L. EuSIP5-overexpressing (OE) plants was delayed by 4 days under drought stress. Additionally, the expression levels of the drought-related genes DET2, CYP85A1, P5CS, ERF1, F-box, and NCED1 were elevated in the leaves of transgenic N. tabacum L. Moreover, the activities of the protective enzymes peroxidase, superoxide dismutase, and catalase were significantly greater, whereas the malondialdehyde content was lower in the transgenic plants than in the WT plants. These findings suggest that the introduction of the EuSIP5 gene into N. tabacum L. enhances drought-related gene expression, increases antioxidant capacity, and reduces oxidative stress damage, thereby improving drought resistance.