title: Nitric oxide metabolism and indole acetic acid biosynthesis cross-talk in Azospirillum brasilense SM.
abstract: Production of nitric oxide (NO) and the presence of NO metabolism genes, nitrous oxide reductase (nosZ), nitrous oxide reductase regulator (nosR) and nitric oxide reductase (norB) were identified in the plant-associated bacterium (PAB) Azospirillum brasilense SM. NO presence was confirmed in all overexpressing strains, while improvement in the plant growth response of these strains was mediated by increased NO and indole-3-acetic acid (IAA) levels in the strains. Electron microscopy showed random distribution to biofilm, with surface colonization of pleiomorphic Azospirilla. Quantitative IAA estimation highlighted a crucial role of nosR and norBC in regulating IAA biosynthesis. The NO quencher and donor reduced/blocked IAA biosynthesis by all strains, indicating their common regulatory role in IAA biosynthesis. Tryptophan (Trp) and l-Arginine (Arg) showed higher expression of NO genes tested, while in the case of ipdC, only Trp and IAA increased expression, while Arg had no significant effect. The highest nosR expression in SMnosR in the presence of IAA and Trp, along with its 2-fold IAA level, confirmed the relationship of nosR overexpression with Trp in increasing IAA. These results indicate a strong correlation between IAA and NO in A. brasilense SM and suggest the existence of cross-talk or shared signaling mechanisms in these two growth regulators.
authors.affiliation: TERI Deakin Nanobiotechnology Centre, Biotechnology and Bioresources Division, The Energy and Resources Institute, Darbari Seth Block, India Habitat Centre, Lodhi Road, New Delhi 110003, India. Electronic address: vatsala.koul@students.teriuniversity.ac.in.
authors.forename: Vatsala
authors.initials: V
authors.lastname: Koul
authors.affiliation: TERI Deakin Nanobiotechnology Centre, Biotechnology and Bioresources Division, The Energy and Resources Institute, Darbari Seth Block, India Habitat Centre, Lodhi Road, New Delhi 110003, India. Electronic address: chandrakant.tripathi@teri.res.in.
authors.forename: Chandrakant
authors.initials: C
authors.lastname: Tripathi
authors.affiliation: TERI Deakin Nanobiotechnology Centre, Biotechnology and Bioresources Division, The Energy and Resources Institute, Darbari Seth Block, India Habitat Centre, Lodhi Road, New Delhi 110003, India. Electronic address: aloka@teri.res.in.
authors.forename: Alok
authors.initials: A
authors.lastname: Adholeya
authors.affiliation: TERI Deakin Nanobiotechnology Centre, Biotechnology and Bioresources Division, The Energy and Resources Institute, Darbari Seth Block, India Habitat Centre, Lodhi Road, New Delhi 110003, India. Electronic address: mandira.malhotra@gmail.com.
authors.forename: Mandira
authors.initials: M
authors.lastname: Kochar
mesh_terms: D001120:Arginine / Q000378:metabolism; D015806:Azospirillum brasilense / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000254:growth & development; D015964:Gene Expression Regulation, Bacterial; D007210:Indoleacetic Acids / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D009569:Nitric Oxide / Q000302:isolation & purification / Q000378:metabolism*; D018517:Plant Roots / Q000382:microbiology / Q000648:ultrastructure; D015398:Signal Transduction; D045868:Sorghum / Q000254:growth & development / Q000382:microbiology*; D014364:Tryptophan / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007210:Indoleacetic Acids; D008565:Membrane Proteins; C075970:NosR protein, Bacteria; D009569:Nitric Oxide; C030737:indoleacetic acid; D014364:Tryptophan; D001120:Arginine
keywords: Azospirillum brasilense; Scanning electron microscopy; ipdC; norBC; nosR; nosZ