Molecular cloning and functional characterisation of an H(+)-pyrophosphatase from Iris lactea

Tonoplast H(+)-pyrophosphatases (VPs) mediate vacuolar Na(+) sequestration, a process important for salt tolerance of plants. The function of VP in the highly drought- and salt-tolerant perennial Iris lactea under salt stress is unclear. Here, we isolated IlVP from I. lactea and investigated its function in transgenic tobacco. IlVP was found to comprise 771 amino acid residues and showed 88% similarity with Arabidopsis AtVP1. IlVP was mainly expressed in shoots and was up-regulated by salt stress. Overexpression of IlVP enhanced growth of transgenic tobacco plants compared with wild-type (WT) plants exposed to salt stress. Transgenic plants accumulated higher quantities of Na(+) and K(+) in leaves, stems, and roots under salt stress, which caused higher leaf relative water content and decreased cell membrane damage compared with WT plants. Overall, IlVP encoding a tonoplast H(+)-pyrophosphatase can reduce Na(+) toxicity in plant cells through increased sequestration of ions into vacuoles by enhanced H(+)-pyrophosphatase activity.