@article{e08fc42bb91b4e6abd9593f67d59843d,
title = "Rice amino acid transporter-like 6 (OsATL6) is involved in amino acid homeostasis by modulating the vacuolar storage of glutamine in roots",
abstract = "Glutamine is a product of ammonium (NH4+) assimilation catalyzed by glutamine synthetase (GS) and glutamate synthase (GOGAT). The growth of NH4+-preferring paddy rice (Oryza sativa L.) depends on root NH4+ assimilation and the subsequent root-to-shoot allocation of glutamine; however, little is known about the mechanism of glutamine storage in roots. Here, using transcriptome and reverse genetics analyses, we show that the rice amino acid transporter-like 6 (OsATL6) protein exports glutamine to the root vacuoles under NH4+-replete conditions. OsATL6 was expressed, along with OsGS1;2 and OsNADH-GOGAT1, in wild-type (WT) roots fed with sufficient NH4Cl, and was induced by glutamine treatment. We generated two independent Tos17 retrotransposon insertion mutants showing reduced OsATL6 expression to determine the function of OsATL6. Compared with segregants lacking the Tos17 insertion, the OsATL6 knock-down mutant seedlings exhibited lower root glutamine content but higher glutamine concentration in the xylem sap and greater shoot growth under NH4+-replete conditions. The transient expression of monomeric red fluorescent protein-fused OsATL6 in onion epidermal cells confirmed the tonoplast localization of OsATL6. When OsATL6 was expressed in Xenopus laevis oocytes, glutamine efflux from the cell into the acidic bath solution increased. Under sufficient NH4+ supply, OsATL6 transiently accumulated in sclerenchyma and pericycle cells, which are located adjacent to the Casparian strip, thus obstructing the apoplastic solute path, and in vascular parenchyma cells of WT roots before the peak accumulation of GS1;2 and NADH-GOGAT1 occurred. These findings suggest that OsATL6 temporarily stores excess glutamine, produced by NH4+ assimilation, in root vacuoles before it can be translocated to the shoot.",
keywords = "Oryza sativa L., amino acid transporter, ammonium assimilation, glutamine transport, roots, vacuoles",
author = "Saori Ogasawara and Masataka Ezaki and Ryusuke Ishida and Kuni Sueyoshi and Shunya Saito and Yuki Hiradate and Toru Kudo and Mitsuhiro Obara and Soichi Kojima and Nobuyuki Uozumi and Kentaro Tanemura and Toshihiko Hayakawa",
note = "Funding Information: The Tos17-insertion mutants were developed by Drs H. Hirochika and A. Miyao (National Institute of Agrobiological Sciences), and the seeds and OsATLa cDNA clones were provided by the RGRC. We thank Dr T. Nakagawa (Shimane University) for providing pUGW55, Dr Y.-F. Tsay (Academia Sinica) for providing pGEMHE, Drs M.H. Sato (Kyoto Prefectural University) and T. Uemura (Tokyo University) for providing sGFP-AtVAM3, Dr Y. Niwa (Shizuoka University) for providing sGFP, Dr R.Y. Tsien (California University) for providing mRFP, Dr P.A. Rea (Pennsylvania University) for providing the anti-V-PPase antibody, and Ms Y. Shiroto and Mr Y. Hongo for experimental assistance. This work was supported in part by a KAKENHI grant (17H03780 to TH) awarded by the Japan Society for the Promotion of Science and a Genomics-based Technology grant for Agricultural Improvement (LCT-0007 to MO) awarded by the Ministry of Agriculture, Forestry and Fisheries of Japan. Funding Information: The ‐insertion mutants were developed by Drs H. Hirochika and A. Miyao (National Institute of Agrobiological Sciences), and the seeds and cDNA clones were provided by the RGRC. We thank Dr T. Nakagawa (Shimane University) for providing pUGW55, Dr Y.‐F. Tsay (Academia Sinica) for providing pGEMHE, Drs M.H. Sato (Kyoto Prefectural University) and T. Uemura (Tokyo University) for providing , Dr Y. Niwa (Shizuoka University) for providing , Dr R.Y. Tsien (California University) for providing , Dr P.A. Rea (Pennsylvania University) for providing the anti‐V‐PPase antibody, and Ms Y. Shiroto and Mr Y. Hongo for experimental assistance. This work was supported in part by a KAKENHI grant (17H03780 to TH) awarded by the Japan Society for the Promotion of Science and a Genomics‐based Technology grant for Agricultural Improvement (LCT‐0007 to MO) awarded by the Ministry of Agriculture, Forestry and Fisheries of Japan. Tos17 OsATLa sGFP‐AtVAM3 sGFP mRFP Publisher Copyright: {\textcopyright} 2021 Society for Experimental Biology and John Wiley & Sons Ltd.",
year = "2021",
month = sep,
doi = "10.1111/tpj.15403",
language = "English",
volume = "107",
pages = "1616--1630",
journal = "Plant Journal",
issn = "0960-7412",
publisher = "Wiley-Blackwell",
number = "6",
}