Molecular cloning and functional characterisation of an H+-pyrophosphatase from &ITIris lactea&IT

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 IIVP from l. lactea and investigated its function in transgenic tobacco. IIVP was found to comprise 771 amino acid residues and showed 88% similarity with Arabidopsis AtVP1. IIVP was mainly expressed in shoots and was up-regulated by salt stress. Overexpression of IIVP 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, IIVP encoding a tonoplast H+-pyrophosphatase can reduce Na+ toxicity in plant cells through increased sequestration of ions into vacuoles by enhanced H+-pyrophosphatase activity.