Biosynthesis of indole‐3‐acetic acid in Azospirillum brasilense

Abstract

Quantum chemical methods AM1 and PM3 and chromatographic methods were used to qualitatively characterize pathways of bacterial production of indole-3-acetic acid (IAA). The standard free energy changes (DG8 H sum ) for the synthesis of tryptophan (Trp) from chorismic acid via anthranilic acid and indole were calculated, as were those for several possible pathways for the synthesis of IAA from Trp, namely via indole-3-acetamide (IAM), indole-3-pyruvic acid (IPyA), and indole-3-acetonitrile (IAN). The DG8 H sum for Trp synthesis from chorismic acid was ± 402 (± 434) kJ´mol ±1 (values in parentheses were calculated by PM3). The DG8 H sum for IAA synthesis from Trp were 2 565 (± 548) kJ´mol ±1 for the IAN pathway, ± 481 (± 506) kJ´mol ±1 for the IAM pathway, and ± 289 (± 306) kJ´mol ±1 for the IPyA pathway. By HPLC analysis, the possibility was assessed that indole, anthranilic acid, and Trp might be utilized as precursors for IAA synthesis by Azospirillum brasilense strain Sp 245. The results indicate that there is a high motive force for Trp synthesis from chorismic acid and for IAA synthesis from Trp, and make it unlikely that anthranilic acid and indole act as the precursors to IAA in a Trp-independent pathway.

Indole-3-acetic acid: A widespread physiological code in interactions of fungi with other organisms

“…22 Zakharova et al 23 showed that several bacterial IAA biosynthetic pathways might exist in Azospirillum brasilense, a nitrogen-fixing bacterium found in the rhizosphere of various grass species. IAA can be synthesized from Trp through IAM, IPA, and IAN pathways in A. brasilense.…”

“…IAA can be synthesized from Trp through IAM, IPA, and IAN pathways in A. brasilense. 23 However, feeding experiments with labeled precursors have indicated that Trp-independent IAA production in A. brasilense is derived from the intermediates of Trp pathways. 4,23 However, no specific enzymes or genes of this pathway have yet been identified, and only a few studies on the IAA biosynthetic pathway in fungi have been conducted.…”

“…23 However, feeding experiments with labeled precursors have indicated that Trp-independent IAA production in A. brasilense is derived from the intermediates of Trp pathways. 4,23 However, no specific enzymes or genes of this pathway have yet been identified, and only a few studies on the IAA biosynthetic pathway in fungi have been conducted. 6,16,24 Feeding experiments and in vitro assays have confirmed the presence of IAM and IPA pathways in the mycoherbicide Colletotrichum gloeosporioides f. sp.…”

Diversidade da microbiota endofítica na cultura da palma (Opuntia spp. e Nopalea spp.) no Semiárido de Pernambuco

“…No entanto, alguns autores sugerem que 80% do ácido indolacético sintetizado por este gênero é derivado de uma via independente da adição de triptofano ao meio de cultura, pois outros compostos podem ser metabolizados (ZAKHAROVA et al, 1999). De acordo com Ona et al (2005), a produção de AIA só ocorre sob condições do que o gene 16S rDNA e os genes rrs (Ribossomais).…”

Exploiting inter-organismal chemical communication for improved inoculants

“…In either case, their effects on plant growth are pronounced. ePGPR increase plant growth directly through the production of phytohormones (Zakharova et al 1999), or the facilitation nutrient uptake (Glick 1995). Indirect promotion of plant growth is through antibiosis via antibiotic type compounds (Maurhofer et al 1992), through siderophores that bind available Fe (Carson et al 2000) or enhanced resistance to biotic stresses and/or abiotic stresses such as frost damage (Sturz et al 2000).…”