Characterization of a vacuolar zinc transporter OZT1 in rice (Oryza sativa L.)

The CDF family is a ubiquitous family that has been identified in prokaryotes, eukaryotes, and archaea. Members of this family are important heavy metal transporters that transport metal ions out of the cytoplasm. In this research, a full length cDNA named Oryza sativa Zn Transporter 1 (OZT1) that closely related to rat ZnT-2 (Zn Transporter 2) gene was isolated from rice. The OZT1 encoding a CDF family protein shares 28.2 % ~ 84.3 % of identities and 49.3 % ~ 90.9 % of similarities with other zinc transporters such as RnZnT-2, HsZnT-8, RnZnT-8 and AtMTP1. OZT1 was constitutively expressed in various rice tissues. The OZT1 expression was significantly induced both in the seedlings of japonica rice Nipponbare and indica rice IR26 in response to Zn(2+) and Cd(2+) treatments. Besides, OZT1 expression was also increased when exposed to other excess metals, such as Cu(2+), Fe(2+) and Mg(2+). Subcellular localization analysis indicated that OZT1 localized to vacuole. Heterologous expression of OZT1 in yeast increased tolerance to Zn(2+) and Cd(2+) stress but not the Mg(2+) stress. Together, OZT1 is a CDF family vacuolar zinc transporter conferring tolerance to Zn(2+) and Cd(2+) stress, which is important to transporting and homeostasis of Zn, Cd or other heavy metals in plants.