Expression of vacuolar H⁺-pyrophosphatase (OVP3) is under control of an anoxia-inducible promoter in rice

Vacuolar H⁺-pyrophosphatase (V-PPase) expression increases in a number of abiotic stresses and is thought to play a role in adaptation to abiotic stresses. This paper reports on the regulation of six V-PPase genes in rice (Oryza sativa L.) coleoptiles under anoxia, using flood tolerant and intolerant cultivars to test our hypothesis. Quantitative PCR analysis showed that one vacuolar H⁺-pyrophosphatase (OVP3) was induced by anoxia, particularly in flood-tolerant rice. Regulation of OVP3 expression under anoxia was investigated by analysing putative OVP promoters. The putative OVP3 promoter contained more previously identified anoxia-inducible motifs than the putative promoters of the other five OVP genes. GUS activity in transgenic rice plants containing the OVP3 promoter region linked to the GUS reporter gene was induced only by anoxia. Salt and cold treatments had little effect on OVP3 promoter-driven GUS expression when compared to the anoxic treatment.