title: Indole-3-acetic acid production via the indole-3-pyruvate pathway by plant growth promoter Rhizobium tropici CIAT 899 is strongly inhibited by ammonium.
abstract: Like many rhizobia, Rhizobium tropici produces indole-3-acetic acid (IAA), an important signal molecule required for root hair infection in rhizobia-legume symbioses. However, the IAA biosynthesis pathway and its regulation by R. tropici are still poorly understood. In this study, IAA synthesis and the effects of mineral N in IAA production by R. tropici CIAT 899 were verified by ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). Furthermore, expression of genes related to IAA biosynthesis and metabolism were evaluated by RT-qPCR. Results indicated that IAA production by CIAT 899 was 12 times lower in the presence of [Formula: see text] . Moreover, it was found that indole-3-pyruvate (IPyA) is the major IAA biosynthesis intermediate. Genes y4wE, lao and iorA were identified by analysis of R. tropici genome in silico and were upregulated by tryptophan, indicating a possible role of these genes in IAA biosynthesis by CIAT 899. In conclusion, we show that IPyA is the major pathway for IAA biosynthesis in CIAT 899 and that its production is strongly inhibited by [Formula: see text] . Although present results arose from in vitro experiments, they provide new insight into the role of nitrogen in early events related to legume nodulation.
authors.affiliation: Laboratório de Genética de Microrganismos, Departamento de Biologia Geral, Universidade Estadual de Londrina, PR-445, Km 380, Campus Universitário, PO Box 6001, CP 86.051-970, Londrina, PR, Brazil. Electronic address: eddie.imada@gmail.com.
authors.forename: Eddie Luidy
authors.initials: EL
authors.lastname: Imada
authors.affiliation: Laboratório de Biotecnologia do Solo, Embrapa Soja, PO Box 231, CP 86.001-970, Londrina, PR, Brazil. Electronic address: amandaaapr@gmail.com.
authors.forename: Amanda Alves de Paiva
authors.initials: AAP
authors.lastname: Rolla Dos Santos
authors.affiliation: Departamento de Bioquímica e Biotecnologia, Universidade Estadual de Londrina, PR-445, Km 380, Campus Universitário, PO Box 6001, CP 86.051-970, Londrina, PR, Brazil. Electronic address: almoliva@uel.br.
authors.forename: André Luiz Martinez de
authors.initials: ALM
authors.lastname: Oliveira
authors.affiliation: Laboratório de Biotecnologia do Solo, Embrapa Soja, PO Box 231, CP 86.001-970, Londrina, PR, Brazil. Electronic address: mariangela.hungria@embrapa.br.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Hungria
authors.affiliation: Laboratório de Genética de Microrganismos, Departamento de Biologia Geral, Universidade Estadual de Londrina, PR-445, Km 380, Campus Universitário, PO Box 6001, CP 86.051-970, Londrina, PR, Brazil. Electronic address: elisete@uel.br.
authors.forename: Elisete Pains
authors.initials: EP
authors.lastname: Rodrigues
mesh_terms: D064751:Ammonium Compounds / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D053898:Biosynthetic Pathways / Q000235:genetics; D007887:Fabaceae / Q000254:growth & development / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics; D010937:Plant Growth Regulators / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D060888:Real-Time Polymerase Chain Reaction; D042162:Rhizobium tropici / Q000187:drug effects / Q000378:metabolism*; D013559:Symbiosis
chemical_list: D064751:Ammonium Compounds; D001426:Bacterial Proteins; D007210:Indoleacetic Acids; D007211:Indoles; D010937:Plant Growth Regulators; C008122:indol-3-yl pyruvic acid; C030737:indoleacetic acid
keywords: Fertilizers; Indoles; Nitrogen fixation; Plant growth regulators; Symbiosis; Tryptophan