title: Alternative mechanism for the evaluation of indole-3-acetic acid (IAA) production by Azospirillum brasilense strains and its effects on the germination and growth of maize seedlings.
abstract: We evaluated the production of indole-3-acetic acid (IAA) by Azospirillum brasilense strains in vitro (cell culture supernatants) and in vivo (stems and roots of maize seedlings) to clarify the role of this phytohormone as a signaling and effector molecule in the symbiotic interaction between maize and A. brasilense. The three strains all showed IAA production when cultured in NFb medium supplemented with 100 μg/ml L-tryptophan. The level of IAA production was 41.5 μg/ml for Yu62, 12.9 μg/ml for Az39, and 0.15 μg/ml for ipdC-. The release of IAA into culture medium by the bacteria appeared to be the main activator of the early growth promotion observed in the inoculated maize seedlings. The application of supernatants with different IAA contents caused significant differences in the seedling growth. This observation provides the basis for novel technological tools for effective quality control procedures on inoculants. The approach described can be incorporated into different inoculation methods, including line sowing, downspout, and foliar techniques, and increase the sustainability of symbiotic plant-bacteria systems.
authors.affiliation: Laboratorio de Fisiología Vegetal, Universidad Nacional de Río Cuarto, 5800, Río Cuarto, Argentina.
authors.forename: Oscar
authors.initials: O
authors.lastname: Masciarelli
authors.forename: Lucia
authors.initials: L
authors.lastname: Urbani
authors.forename: Herminda
authors.initials: H
authors.lastname: Reinoso
authors.forename: Virginia
authors.initials: V
authors.lastname: Luna
mesh_terms: D015806:Azospirillum brasilense / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D018525:Germination / Q000187:drug effects*; D007210:Indoleacetic Acids / Q000378:metabolism*; D063245:Plant Development / Q000187:drug effects*; D036226:Seedlings / Q000187:drug effects / Q000382:microbiology; D014364:Tryptophan / Q000378:metabolism; D003313:Zea mays / Q000187:drug effects* / Q000382:microbiology*
chemical_list: D003470:Culture Media; D007210:Indoleacetic Acids; C030737:indoleacetic acid; D014364:Tryptophan
references.citation: Environ Microbiol. 2008 May;10(5):1365-73
references.pmid: 18248455
references.citation: FEMS Microbiol Lett. 2005 May 1;246(1):125-32
references.pmid: 15869971
references.citation: Plant Physiol. 1988;86:890-4
references.pmid: 11538240
references.citation: Appl Microbiol Biotechnol. 2009 Nov;85(2):371-81
references.pmid: 19655138
references.citation: Can J Microbiol. 2004 Aug;50(8):521-77
references.pmid: 15467782
references.citation: Appl Microbiol Biotechnol. 2007 Jul;75(5):1143-50
references.pmid: 17345081
references.citation: BMC Microbiol. 2008 Dec 22;8:231
references.pmid: 19099608
references.citation: Plant Physiol. 1984 Oct;76(2):342-6
references.pmid: 16663844
references.citation: Plant Physiol. 1985;77:824-7
references.pmid: 11539043
references.citation: Eur J Biochem. 1999 Feb;259(3):572-6
references.pmid: 10092839
references.citation: Appl Environ Microbiol. 1983 Jun;45(6):1775-9
references.pmid: 16346311
references.citation: Mol Gen Genet. 1991 Sep;229(1):41-51
references.pmid: 1896020