Disruption of the rice nitrate transporter OsNPF2.2 hinders root-to-shoot nitrate transport and vascular development.
Plants have evolved to express some members of the nitrate transporter 1/peptide transporter family (NPF) to uptake and transport nitrate. However, little is known of the physiological and functional roles of this family in rice (Oryza sativa L.). Here, we characterized the vascular specific transporter OsNPF2.2. Functional analysis using cDNA-injected Xenopus laevis oocytes revealed that OsNPF2.2 is a low-affinity, pH-dependent nitrate transporter. Use of a green fluorescent protein tagged OsNPF2.2 showed that the transporter is located in the plasma membrane in the rice protoplast. Expression analysis showed that OsNPF2.2 is nitrate inducible and is mainly expressed in parenchyma cells around the xylem. Disruption of OsNPF2.2 increased nitrate concentration in the shoot xylem exudate when nitrate was supplied after a deprivation period; this result suggests that OsNPF2.2 may participate in unloading nitrate from the xylem. Under steady-state nitrate supply, the osnpf2.2 mutants maintained high levels of nitrate in the roots and low shoot:root nitrate ratios; this observation suggests that OsNPF2.2 is involved in root-to-shoot nitrate transport. Mutation of OsNPF2.2 also caused abnormal vasculature and retarded plant growth and development. Our findings demonstrate that OsNPF2.2 can unload nitrate from the xylem to affect the root-to-shoot nitrate transport and plant development.
Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement &Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
Yuge
Y
Li
Rice Institute, Chongqing Academy of Agricultural Sciences, Chongqing 401329, China.
Jie
J
Ouyang
Department of Life Science, National Taiwan University, Taipei, Taiwan.
Ya-Yun
YY
Wang
1] Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement &Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China [2] University of Chinese Academy of Sciences, Beijing 100049, China.
Rui
R
Hu
Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement &Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
Kuaifei
K
Xia
Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement &Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
Jun
J
Duan
Guangdong Key Lab of Biotechnology for Plant Development, College of Life Science, South China Normal University, Guangzhou 510631, China.
Yaqin
Y
Wang
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Yi-Fang
YF
Tsay
Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement &Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
Mingyong
M
Zhang
D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism; D052584:Xylem / Q000378:metabolism
D027321:Anion Transport Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins