Tryptophan-Independent Indole-3-Acetic Acid Synthesis: Critical Evaluation of the Evidence

Nonhebel, Heather M.

doi:10.1104/pp.15.01091

Cited by 45 publications

(24 citation statements)

References 31 publications

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“…IAA biosynthesis consists of a complex set of tryptophan dependent and independent pathways that is not yet fully understood (Zhao, 2010 ; Tivendale et al, 2014 ). The tryptophan independent pathway remains genetically undefined (Normanly, 2010 ; Nonhebel, 2015 ). In contrast, the tryptophan dependent pathways have been well studied in A. thaliana (Sztein et al, 2000 ; Zhao, 2010 ), with many of the genes encoding for its enzymes functionally described.…”

Section: Resultsmentioning

confidence: 99%

Indole-3-Acetic Acid Is Produced by Emiliania huxleyi Coccolith-Bearing Cells and Triggers a Physiological Response in Bald Cells

et al. 2016

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Indole-3-acetic acid (IAA) is an auxin produced by terrestrial plants which influences development through a variety of cellular mechanisms, such as altering cell orientation, organ development, fertility, and cell elongation. IAA is also produced by bacterial pathogens and symbionts of plants and algae, allowing them to manipulate growth and development of their host. They do so by either producing excess exogenous IAA or hijacking the IAA biosynthesis pathway of their host. The endogenous production of IAA by algae remains contentious. Using Emiliania huxleyi, a globally abundant marine haptophyte, we investigated the presence and potential role of IAA in algae. Homologs of genes involved in several tryptophan-dependent IAA biosynthesis pathways were identified in E. huxleyi. This suggests that this haptophyte can synthesize IAA using various precursors derived from tryptophan. Addition of L-tryptophan to E. huxleyi stimulated IAA production, which could be detected using Salkowski's reagent and GC × GC-TOFMS in the C cell type (coccolith bearing), but not in the N cell type (bald). Various concentrations of IAA were exogenously added to these two cell types to identify a physiological response in E. huxleyi. The N cell type, which did not produce IAA, was more sensitive to it, showing an increased variation in cell size, membrane permeability, and a corresponding increase in the photosynthetic potential quantum yield of Photosystem II (PSII). A roseobacter (bacteria commonly associated with E. huxleyi) Ruegeria sp. R11, previously shown to produce IAA, was co-cultured with E. huxleyi C and N cells. IAA could not be detected from these co-cultures, and even when stimulated by addition of L-tryptophan, they produced less IAA than axenic C type culture similarly induced. This suggests that IAA plays a novel role signaling between different E. huxleyi cell types, rather than between a bacteria and its algal host.

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Section: Resultsmentioning

confidence: 99%

Indole-3-Acetic Acid Is Produced by Emiliania huxleyi Coccolith-Bearing Cells and Triggers a Physiological Response in Bald Cells

et al. 2016

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“…The biosynthesis of IAA as a natural auxin could be mediated by two main directions: via an l -tryptophan ( l -Trp)-dependent or an l -Trp-independent pathway [ 46 , 47 ] ( Figure 2 ). De novo synthesis through the l -Trp-independent pathway is well described in microorganisms [ 48 ] but still discussed in higher plants [ 49 , 50 ]. In contrast, l -Trp-dependent pathways are a significant source of endogenous IAA for higher plants [ 40 ], as l -Trp is synthesized by the shikimate pathway localized in the chloroplast stroma.…”

Section: Auxinsmentioning

confidence: 99%

Auxins and Cytokinins—The Role of Subcellular Organization on Homeostasis

Skalický

Kubeš

Napier

et al. 2018

IJMS

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Plant hormones are master regulators of plant growth and development. Better knowledge of their spatial signaling and homeostasis (transport and metabolism) on the lowest structural levels (cellular and subcellular) is therefore crucial to a better understanding of developmental processes in plants. Recent progress in phytohormone analysis at the cellular and subcellular levels has greatly improved the effectiveness of isolation protocols and the sensitivity of analytical methods. This review is mainly focused on homeostasis of two plant hormone groups, auxins and cytokinins. It will summarize and discuss their tissue- and cell-type specific distributions at the cellular and subcellular levels.

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“…In the case of the tryptophan-dependent pathway, the tryptophan is converted to indole-3-piruvate by the TRYPTOPHAN AMINO TRANSFERASE, and then by the action of YUCCA family monooxygenase, the indole-3-piruvate is converted to IAA (Kasahara 2015;Tivendale et al 2014;Zhao 2014). On the other hand, the Ax biosynthesis tryptophan-independent involves the conversion of IBA to IAA, via β-oxidation in the peroxisomes (Nonhebel 2015;Wang et al 2015).…”

Section: Introductionmentioning

confidence: 98%

The Role of the Auxins During Somatic Embryogenesis

Nic-Can

Loyola‐Vargas

2016

Somatic Embryogenesis: Fundamental Aspects and Applications

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It is well known that auxins (Ax) and cytokinins (Ck) are key regulators of plant cell division and differentiation. These growth regulators can induce plant cell reprogramming. The balance between Ax and Ck during their application in the plant tissue culture determines the state of cell di-or dedifferentiation. Other plant growth regulators can also induce callus. However, Ax is the most widely used plant growth regulator to control organ regeneration, callus induction or somatic embryogenesis induction. Ax plays a central role in early and post-embryogenic plant development. Elegant studies have shown that temporal and spatial Ax distribution mediates important steps during the early embryo patterning formation of zygotic embryogenesis (ZE). The application of exogenous Ax into the culture medium can unbalance the endogenous of this growth regulator and modify the IAA metabolism inside the cell. In most of the cultures, it has been demonstrated that the removal of the exogenous Ax from of culture medium promotes the formation of embryogenic structures. The increment in the endogenous Ax regulates the expression of a great number of transcription factors, several of them related to stress. The other aspect about the homeostasis of Ax, which has an effect on the induction of somatic embryogenesis, is its transport. In this chapter, a revision and analysis about the role of Ax in different aspects of somatic embryogenesis is made.

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Tryptophan-Independent Indole-3-Acetic Acid Synthesis: Critical Evaluation of the Evidence

Cited by 45 publications

References 31 publications

Indole-3-Acetic Acid Is Produced by Emiliania huxleyi Coccolith-Bearing Cells and Triggers a Physiological Response in Bald Cells

Indole-3-Acetic Acid Is Produced by Emiliania huxleyi Coccolith-Bearing Cells and Triggers a Physiological Response in Bald Cells

Auxins and Cytokinins—The Role of Subcellular Organization on Homeostasis

The Role of the Auxins During Somatic Embryogenesis

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