title: Polyamine Resistance Is Increased by Mutations in a Nitrate Transporter Gene NRT1.3 (AtNPF6.4) in Arabidopsis thaliana.
abstract: Polyamines are small basic compounds present in all living organisms and act in a variety of biological processes. However, the mechanism of polyamine sensing, signaling and response in relation to other metabolic pathways remains to be fully addressed in plant cells. As one approach, we isolated Arabidopsis mutants that show increased resistance to spermine in terms of chlorosis. We show here that two of the mutants have a point mutation in a nitrate transporter gene of the NRT1/PTR family (NPF), NRT1.3 (AtNPF6.4). These mutants also exhibit increased resistance to putrescine and spermidine while loss-of-function mutants of the two closest homologs of NRT1.3, root-specific NRT1.1 (AtNPF6.3) and petiole-specific NRT1.4 (AtNPF6.2), were shown to have a normal sensitivity to polyamines. When the GUS reporter gene was expressed under the control of the NRT1.3 promoter, GUS staining was observed in leaf mesophyll cells and stem cortex cells but not in the epidermis, suggesting that NRT1.3 specifically functions in parenchymal tissues. We further found that the aerial part of the mutant seedling has normal levels of polyamines but shows reduced uptake of norspermidine compared with the wild type. These results suggest that polyamine transport or metabolism is associated with nitrate transport in the parenchymal tissue of the shoot.
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University Okayama, Japan.
authors.forename: Wurina
authors.initials: W
authors.lastname: Tong
authors.affiliation: National Institute for Basic Biology Okazaki, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Imai
authors.affiliation: Graduate School of Science and Technology, Kumamoto University Kumamoto, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Tabata
authors.affiliation: National Institute for Basic Biology Okazaki, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Shigenobu
authors.affiliation: National Institute for Basic Biology Okazaki, Japan.
authors.forename: Katsushi
authors.initials: K
authors.lastname: Yamaguchi
authors.affiliation: National Institute for Basic BiologyOkazaki, Japan; Department of Biology, Duke UniversityDurham, NC, USA.
authors.forename: Masashi
authors.initials: M
authors.lastname: Yamada
authors.affiliation: National Institute for Basic Biology Okazaki, Japan.
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Hasebe
authors.affiliation: Graduate School of Science and Technology, Kumamoto University Kumamoto, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Sawa
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University Okayama, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Motose
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University Okayama, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Takahashi
keywords: Arabidopsis; NRT1/PTR family; nitrate transporter; parenchymal tissue; polyamines