scholarly journals Double agent indole-3-acetic acid (IAA): Mechanistic analysis of indole-3-acetaldehyde dehydrogenase AldA that synthesizes IAA, an auxin that aids bacterial virulence

2021 ◽  
Author(s):  
Ateek Shah ◽  
Yamini Mathur ◽  
Amrita Hazra
Keyword(s):  
Acetic Acid ◽  
Pseudomonas Syringae ◽  
Active Site ◽  
Industrial Applications ◽  
Active Site Residues ◽  
Innovative Methods ◽  
Mechanistic Analysis ◽  
Double Agent ◽  
Indole 3 Acetic Acid ◽  
Bacterial Plant Pathogen

The large diversity of organisms inhabiting various environmental niches on our planet are engaged in a lively exchange of biomolecules, including nutrients, hormones, and vitamins. In a quest to survive, organisms that we define as pathogens employ innovative methods to extract valuable resources from their host leading to an infection. One such instance is where plant-associated bacterial pathogens synthesize and deploy hormones or their molecular mimics to manipulate the physiology of the host plant. This commentary describes one such specific example - the mechanism of the enzyme AldA, an aldehyde dehydrogenase (ALDH) from the bacterial plant pathogen Pseudomonas syringae which produces the plant auxin hormone indole-3-acetic acid (IAA) by oxidizing the substrate indole-3-acetaldehyde (IAAld) using the cofactor NAD+ (Bioscience Reports, 2020, 40, https://doi.org/10.1042/BSR20202959). Using mutagenesis, enzyme kinetics, and structural analysis, Zhang K. et al., establish that the progress of the reaction hinges on the formation of two distinct conformations of NAD(H) during the reaction course. Additionally, a key mutation in the AldA active site ‘aromatic box’ changes the enzyme’s preference for an aromatic substrate to an aliphatic one. Our commentary concludes that such molecular level investigations help to establish the nature of the dynamics of NAD(H) in ALDH-catalysed reactions, and further show that key active site residues control substrate specificity. We also contemplate that insights from this study can be used to engineer novel ALDH enzymes for environmental, health and industrial applications.

Characterization of the indole-3-acetic acid (IAA) biosynthetic pathway in an epiphytic strain of Erwinia herbicola and IAA production in vitro

1996 ◽  
Vol 42 (6) ◽  
pp. 586-592 ◽  
Author(s):  
M. Brandi ◽  
E. M. Clark ◽  
S. E. Lindow
Keyword(s):  
Acetic Acid ◽  
Pseudomonas Syringae ◽  
Pyruvic Acid ◽  
Enzyme Assays ◽  
Erwinia Herbicola ◽  
Iaa Production ◽  
Acid Pathway ◽  
Culture Supernatants ◽  
Indole 3 Acetic Acid

An epiphytic strain of Erwinia herbicola (strain 299R) synthesized indole-3-acetic acid (IAA) from indole-3-pyruvic acid and indole-3-acetaldehyde, but not from indole-3-acetamide and other intermediates of various IAA biosynthetic pathways in enzyme assays. TLC, HPLC, and GC–MS analyses revealed the presence of indole-3-pyruvic acid, indole-3-ethanol, and IAA in culture supernatants of strain 299R. Indole-3-acetaldehyde was detected in enzyme assays. Furthermore, strain 299R genomic DNA shared no homology with the iaaM and iaaH genes from Pseudomonas syringae pv. savastanoi, even in Southern hybridizations performed under low-stringency conditions. These observations strongly suggest that unlike gall-forming bacteria which can synthesize IAA by indole-3-acetamide, the indole-3-pyruvic acid pathway is the primary route for IAA biosynthesis in this plant-associated strain. IAA synthesis in tryptophan-supplemented cultures of strain 299R was over 10-fold higher under nitrogen-limiting conditions, indicating a possible role for IAA production by bacterial epiphytes in the acquisition of nutrients during growth in their natural habitat.Key words: indole-3-acetic acid, Erwinia, tryptophan, indole-3-pyruvic acid, nitrogen.

Identification of IAA-regulated genes in Pseudomonas syringae pv. tomato strain DC3000

2021 ◽  
Author(s):  
Arnaud-Thierry Djami-Tchatchou ◽  
Zipeng Alex Li ◽  
Paul Stodghill ◽  
Melanie J. Filiatrault ◽  
Barbara N. Kunkel
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Acetic Acid ◽  
Stress Response ◽  
Pseudomonas Syringae ◽  
Plant Pathogen ◽  
Type Iii Secretion ◽  
Plant Hormone ◽  
Indole 3 Acetic Acid ◽  
Exogenous Iaa

The auxin indole-3-acetic acid (IAA) is a plant hormone that not only regulates plant growth and development but also plays important roles in plant-microbe interactions. We previously reported that IAA alters expression of several virulence-related genes in the plant pathogen Pseudomonas syringae pv. tomato strain DC3000 ( Pto DC3000). To learn more about the impact of IAA on regulation of Pto DC3000 gene expression we performed a global transcriptomic analysis of bacteria grown in culture, in the presence or absence of exogenous IAA. We observed that IAA repressed expression of genes involved in the Type III secretion (T3S) system and motility and promoted expression of several known and putative transcriptional regulators. Several of these regulators are orthologs of factors known to regulate stress responses and accordingly expression of several stress response-related genes was also upregulated by IAA. Similar trends in expression for several genes were also observed by RT-qPCR. Using an Arabidopsis thaliana auxin receptor mutant that accumulates elevated auxin, we found that many of the P. syringae genes regulated by IAA in vitro were also regulated by auxin in planta . Collectively the data indicate that IAA modulates many aspects of Pto DC3000 biology, presumably to promote both virulence and survival under stressful conditions, including those encountered in or on plant leaves. IMPORTANCE Indole-3-acetic acid (IAA), a form of the plant hormone auxin, is used by many plant-associated bacteria as a cue to sense the plant environment. Previously, we showed that IAA can promote disease in interactions between the plant pathogen Pseudomonas syringae strain Pto DC000 and one of its hosts, Arabidopsis thaliana . However, the mechanisms by which IAA impacts the biology of Pto DC3000 and promotes disease are not well understood. Here we demonstrate that IAA is a signal molecule that regulates gene expression in Pto DC3000. The presence of exogenous IAA affects expression of over 700 genes in the bacteria, including genes involved in Type III secretion and genes involved in stress response. This work offers insight into the roles of auxin promoting pathogenesis.

scholarly journals Indole-3-Acetaldehyde Dehydrogenase-dependent Auxin Synthesis Contributes to Virulence ofPseudomonas syringaeStrain DC3000

2017 ◽  
Author(s):  
Sheri A. McClerklin ◽  
Soon Goo Lee ◽  
Ron Nwumeh ◽  
Joseph M. Jez ◽  
Barbara N. Kunkel
Keyword(s):  
Acetic Acid ◽  
Pseudomonas Syringae ◽  
Virulence Factors ◽  
Plant Hormone ◽  
Disease Development ◽  
Hormone Signaling ◽  
Host Defenses ◽  
Acetaldehyde Dehydrogenase ◽  
Indole 3 Acetic Acid

AbstractThe bacterial pathogenPseudomonas syringaemodulates plant hormone signaling to promote infection and disease development.P. syringaeuses several strategies to manipulate auxin physiology inArabidopsis thalianato promote pathogenesis, including synthesis of indole-3-acetic acid (IAA), the predominant form of auxin in plants, and production of virulence factors that alter auxin responses in the host; however, the role of pathogen-derived auxin inP. syringaepathogenesis is not well understood. Here we demonstrate thatP. syringaestrain DC3000 produces IAA via a previously uncharacterized pathway and identify a novel indole-3-acetaldehyde dehydrogenase, AldA, that functions in IAA biosynthesis by catalyzing the NAD-dependent formation of IAA from indole-3-acetaldehyde (IAAld). Biochemical analysis and solving of the 1.9 Å resolution x-ray crystal structure reveal key features of AldA for IAA synthesis, including the molecular basis of substrate specificity. Disruption ofaldAand a close homolog,aldB, lead to reduced IAA production in culture and reduced virulence onA. thaliana.We use these mutants to explore the mechanism by which pathogen-derived auxin contributes to virulence and show that IAA produced by DC3000 suppresses salicylic acid-mediated defenses inA. thaliana.Thus, auxin is a DC3000 virulence factor that promotes pathogenicity by suppressing host defenses.Author SummaryPathogens have evolved multiple strategies for suppressing host defenses and modulating host physiology to promote colonization and disease development. For example, the plant pathogenPseudomonas syringaeuses several strategies to the manipulate hormone signaling of its hosts, including production of virulence factors that alter hormone responses in and synthesis of plant hormones or hormone mimics. Synthesis of indole-3-acetic acid (IAA), a common form of the plant hormone auxin, by many plant pathogens has been implicated in virulence. However, the role of pathogen-derived IAA during pathogenesis by leaf spotting pathogens such asP. syringaestrain DC3000 is not well understood. Here, we demonstrate thatP. syringaestrain DC3000 uses a previously uncharacterized biochemical pathway to synthesize IAA, catalyzed by a novel aldehyde dehydrogenase, AldA, and carry out biochemical and structural studies of the AldA protein to investigate AldA activity and substrate specificity. We also generate analdAmutant disrupted in IAA synthesis to show that IAA is a DC3000 virulence factor that promotes pathogenesis by suppressing host defense responses.

scholarly journals Occurrence of Indole-3-Acetic Acid-Producing Bacteria on Pear Trees and Their Association with Fruit Russet

1998 ◽  
Vol 88 (11) ◽  
pp. 1149-1157 ◽  
Author(s):  
Steven E. Lindow ◽  
Caroline Desurmont ◽  
Rachel Elkins ◽  
Glenn McGourty ◽  
Ellen Clark ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Pseudomonas Fluorescens ◽  
Pseudomonas Syringae ◽  
High Performance ◽  
Culture Media ◽  
Bacterial Populations ◽  
Chromatography Analysis ◽  
Population Sizes ◽  
Acid Producing Bacteria ◽  
Indole 3 Acetic Acid

A relatively high percentage of epiphytic bacteria on pear leaf and fruit surfaces had the ability to produce indole-3-acetic acid (IAA) in culture media supplemented with tryptophan. While over 50% of the strains produced at least small amounts of IAA in culture, about 25% of the strains exhibited high IAA production as evidenced by both colorimetric and high-performance liquid chromatography analysis of culture supernatants. A majority of the strains that produced high amounts of IAA were identified as Erwinia herbicola (Pantoea agglomerans), while some strains of Pseudomonas syringae, Pseudomonas viridiflava, Pseudomonas fluorescens, Pseudomonas putida, and Rahnella aquaticus that produced high amounts of IAA also were found on pear. Fruit russeting was significantly increased in 39 out of 46 trials over an 8-year period in which IAA-producing bacteria were applied to trees compared with control trees. A linear relationship was observed between fruit russet severity and the logarithm of the population size of different IAA-producing bacteria on trees in the 30 days after inoculation, when normalized for the amount of IAA produced by each strain in culture. On average, the severity of fruit russet was only about 77% that on control trees when trees were treated at the time of bloom with Pseudomonas fluorescens strain A506, which does not produce IAA. Both total bacterial populations on pear in the 30-day period following full bloom and fruit russet severity varied greatly from year to year and in different commercial orchards over a 10-year period. There was a strong linear correlation between the logarithm of total bacterial population sizes and fruit russet severity.

scholarly journals Auxin Production Is a Common Feature of Most Pathovars of Pseudomonas syringae

1998 ◽  
Vol 11 (2) ◽  
pp. 156-162 ◽  
Author(s):  
Eric Glickmann ◽  
Louis Gardan ◽  
Sylvie Jacquet ◽  
Shafik Hussain ◽  
Miena Elasri ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Pseudomonas Syringae ◽  
Related Species ◽  
Gene Encoding ◽  
Iaa Production ◽  
Auxin Production ◽  
Indole 3 Acetic Acid

We investigated indole-3-acetic acid (IAA) production by 57 pathovars of Pseudomonas syringae and related species. Most of those analyzed produced IAA, especially in the presence of tryptophan. Eight strains produced high IAA concentrations in the absence of Trp. The iaaM and iaaH genes of P. savastanoi pv. savastanoi were detected in a limited number of strains only, including the eight above-mentioned strains. Thus, IAA synthesis in most assayed strains of P. syringae and related species does not involve genes highly similar to iaaM and iaaH. In contrast, the iaaL gene encoding an IAA-lysine synthase was detected in most pathovars, and was often found on plasmids.

scholarly journals Screening of metabolites from endophytic fungi of some Nigerian medicinal plants for antimicrobial activities

2019 ◽  
Vol 3 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Peter M. Eze ◽  
Joy C. Nnanna ◽  
Ugochukwu Okezie ◽  
Happiness S. Buzugbe ◽  
Chika C. Abba ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Secondary Metabolites ◽  
Endophytic Fungi ◽  
Hplc Analysis ◽  
Antimicrobial Activities ◽  
Industrial Applications ◽  
Diffusion Method ◽  
Fungal Isolation ◽  
Indole 3 Acetic Acid ◽  
Fungal Extracts

AbstractEndophytic fungi associated with Nigerian plants have recently generated significant interest in drug discovery programmes due to their immense potential to contribute to the discovery of new bioactive compounds. This study was carried out to investigate the secondary metabolites of endophytic fungi isolated from leaves ofNewbouldia laevis, Ocimum gratissimum, andCarica papayaThe plants were collected from Agulu, Anambra State, South-East Nigeria. Endophytic fungal isolation, fungal fermentation; and extraction of secondary metabolites were carried out using standard methods. The crude extracts were screened for antimicrobial activities using the agar well diffusion method, and were also subjected to high performance liquid chromatography (HPLC) analysis to identify their constituents. A total of five endophytic fungi was isolated, two fromN. laevis(NL-L1 and NL-L2), one fromO. gratissimum(SL-L1), and two fromC. papaya(PPL-LAC and PPL-LE2). In the antimicrobial assay, the extracts of NL-L2, SL-L1, and PPL-LE2 displayed mild antibacterial activity against both Gram negative and Gram positive test bacteria. PPL-LAC extract showed mild activity only againstS. aureus, while no antimicrobial activity was recorded for NL-L1 extract. All the endophytic fungal extracts showed no activity against the test fungiC. albicansandA. fumigatusHPLC analysis of the fungal extracts revealed the presence of ethyl 4-hydroxyphenyl acetate and ferulic acid in NL-L1; ruspolinone in NL-L2; protocatechuic acid, scytalone, and cladosporin in SL-L1; indole-3-acetic acid and indole-3-carbaldehyde in PPL-LE2; and indole-3-acetic acid in PPL-LAC. The findings of this study revealed the potentials possessed by these plants as source of endophytes that express biological active compounds. These endophytes hold key of possibilities to the discovery of novel molecules for pharmaceutical, agricultural and industrial applications.

α-N-acetyl-indole-3-acetyl-ε-L-lysine: A metabolite of indole-3-acetic acid from Pseudomonas syringae pv. savastanoi

1985 ◽  
Vol 25 (1) ◽  
pp. 125-128 ◽  
Author(s):  
Antonio Evidente ◽  
Giuseppe Surico ◽  
Nicola S. Iacobellis ◽  
Giacomino Randazzo
Keyword(s):  
Acetic Acid ◽  
Pseudomonas Syringae ◽  
Indole 3 Acetic Acid
Sign in / Sign up

Export Citation Format

Share Document