title: Gene expression and localization of a β-1,3-glucanase of Lotus japonicus.
abstract: Phytohormone abscisic acid (ABA) inhibits root nodule formation of leguminous plants. LjGlu1, a β-1,3-glucanase gene of Lotus japonicus, has been identified as an ABA responsive gene. RNA interference of LjGlu1 increased nodule number. This suggests that LjGlu1 is involved in the regulation of nodule formation. Host legumes control nodule number by autoregulation of nodulation (AON), in which the presence of existing root nodules inhibits further nodulation. For further characterization of LjGlu1, we focused on the expression of LjGlu1 in relation to AON. In a split-root system, LjGlu1 expression peaked when AON was fully induced. Hairy roots transformed with LjCLE-RS1, a gene that induces AON, were generated. Expression of LjGlu1 was greater in the transgenic roots than in untransformed roots. LjGlu1 was not induced in a hypernodulating mutant inoculated with Mesorhizobium loti. These results suggest that the expression of LjGlu1 is involved in the system of AON. However, neither hypernodulation nor enlarged nodulation zone was observed on the transgenic hairy roots carrying LjGlu1-RNAi, suggesting that LjGlu1 is not a key player of AON. Recombinant LjGlu1 showed endo-β-1,3-glucanase activity. LjGlu1-mOrange fusion protein suggested that LjGlu1 associated with M. loti on the root hairs. Exogenous β-1,3-glucanase inhibited infection thread formation by both the wild type and the mutant, and nodule numbers were reduced. These results suggest that LjGlu1 is expressed in response to M. loti infection and functions outside root tissues, resulting in the inhibition of infection.
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Ken-Ichi
authors.initials: KI
authors.lastname: Osuki
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Hashimoto
authors.affiliation: Department of Environmental Science, Saga University, 1 Honjo-machi, Saga, 840-8502, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.|Developmental Neurobiology Unit, Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Araragi
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Takahara
authors.affiliation: Department of Chemistry and Bioscience, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Kurosawa
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Ken-Ichi
authors.initials: KI
authors.lastname: Kucho
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Higashi
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Abe
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065, Japan. uttan@sci.kagoshima-u.ac.jp.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Uchiumi
mesh_terms: D018506:Gene Expression Regulation, Plant; D043326:Glucan 1,3-beta-Glucosidase / Q000235:genetics* / Q000378:metabolism; D000070116:Lotus / Q000201:enzymology* / Q000235:genetics* / Q000382:microbiology; D059128:Mesorhizobium / Q000502:physiology; D009154:Mutation / Q000235:genetics; D055170:Plant Root Nodulation / Q000235:genetics; D030821:Plants, Genetically Modified; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D053204:Root Nodules, Plant / Q000378:metabolism / Q000382:microbiology; D014170:Transformation, Genetic
chemical_list: D011994:Recombinant Proteins; D043326:Glucan 1,3-beta-Glucosidase
keywords: Infection; Legume; Lotus japonicus; Mesorhizobium loti; Nodulation; β-1,3-glucanase