Abstract: Selenium (Se) is an essential microelement for human, and Se enriched products are important sources for Se intake in human. Tea plants (Camellia sinensis) have strong selenium enrichment ability. However, there is limited research on the molecular mechanism of phosphate transporters involved in Se absorption. In this study, CsPHT1;3 gene was cloned and its characteristics and responses to Se concentrations, valence, pH, time and expression in various Se-enriched tea resources were investigated. Gene characteristic analysis of CsPHT1;3 shows that CsPHT1;3 is grouped into phosphate transporter PHT1 subfamily and localized in the plasma membrane. The CsPHT1;3 protein contains the conserved domain GGDYPLSATIxSE, which belongs to the PHT1 protein. Expression pattern analysis of CsPHT1;3 in various tissues suggests that the expression levels of CsPHT1;3 in mature leaves and root tissues were significantly higher than those in other tissues. The induction results of different Se concentrations and valence states indicate that CsPHT1;3 was significantly induced by Se⁴⁺ at 1 d and 7 d after treatments. The expression of CsPHT1;3 in roots was obviously induced by Se⁶⁺ except for 3 d after treatment but largely unaffected by Se⁶⁺ concentration. The results of different pH and Se⁴⁺ treatments show that, at pH5, the highest expression of CsPHT1;3 in tea roots was observed at 24 h. While at pH3, the highest expression of CsPHT1;3 in tea roots was observed at 48 h. Moreover, at pH7, the highest expression of CsPHT1;3 in tea roots was observed at 72 h. The results of sodium selenate treatment on different Se-enriched tea resources indicate that the expression of CsPHT1;3 in the leaves and roots did not respond to sodium selenate treatment. However, the results of sodium selenite treatment on different Se-enriched tea resources suggest that CsPHT1;3 is significantly up-regulated in the leaves of Se-enriched tea resources. The above studies indicated that CsPHT1;3 may participate in the absorption and redistribution of selenite by roots in tea plants, which is important for the breeding of Se-enriched tea cultivars.

Key words: tea plants, Se intake, selenite, selenium, pH