OsPTR9 can enhance nitrogen use efficiency, growth and grain yield of rice
Zhongming Fang¹, Xing Yang¹, Kuaifei Xia¹, Marianne Suter Grotemeyer², Stefan Meier², Doris Rentsch², Mingyong Zhang^1*

¹Key Laboratory of South China Agricultural Plant Genetics and Breeding, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;
² Institute of Plant Sciences, University of Bern, Altenbergrain21, 3013 Bern, Switzerland.
*Correspondence author: e-mail zhangmy@scbg.ac.cn, Tel: +20 3725 2891

Abstract
The rice PTR/NRT1 (peptide transporter/nitrate transporter 1) gene family comprises a total of 83 di/tripeptide and low affinity nitrate transporters. In Arabidopsis; some members also recognize other substrates like carboxylates, auxin, abscisic acid (ABA) or the defence compound glucosinolate. Little is known about members of this gene family in rice (Oryza sativa L.). Here, we show that the altered OsPTR9 expression affects on nitrogen use efficiency, growth and grain yield. OsPTR9 expression is regulated by the exogenous N source and by the day-night cycle. Increased expression of OsPTR9 in transgenic rice plants resulted in enhanced ammonium uptake, promotion of lateral root formation, and increased grain yield. On the other hand, down-regulation of OsPTR9 in a T-DNA insertion line (osptr9) and in the OsPTR9-RNAi rice plants had the opposite effect. These results suggest that OsPTR9 may hold potential in improving nitrogen use efficiency and grain yield for rice breeding.

Key words: peptide, nitrate, transporter, OsPTR9, rice, grain yield