scholarly journals Investigating the reaction and substrate preference of indole-3-acetaldehyde dehydrogenase from the plant pathogen Pseudomonas syringae PtoDC3000

2020 ◽  
Vol 40 (12) ◽  
Author(s):  
Kaleena Zhang ◽  
Josephine S. Lee ◽  
Regina Liu ◽  
Zita T. Chan ◽  
Trenton J. Dawson ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Pathogen ◽  
Aromatic Aldehydes ◽  
Site Directed Mutagenesis ◽  
Acetaldehyde Dehydrogenase ◽  
Aldehyde Dehydrogenases ◽  
Enzyme Superfamily ◽  
Model Plant Arabidopsis Thaliana ◽  
Indole 3 Acetic Acid ◽  
Plant Arabidopsis Thaliana

Abstract Aldehyde dehydrogenases (ALDHs) catalyze the conversion of various aliphatic and aromatic aldehydes into corresponding carboxylic acids. Traditionally considered as housekeeping enzymes, new biochemical roles are being identified for members of ALDH family. Recent work showed that AldA from the plant pathogen Pseudomonas syringae strain PtoDC3000 (PtoDC3000) functions as an indole-3-acetaldehyde dehydrogenase for the synthesis of indole-3-acetic acid (IAA). IAA produced by AldA allows the pathogen to suppress salicylic acid-mediated defenses in the model plant Arabidopsis thaliana. Here we present a biochemical and structural analysis of the AldA indole-3-acetaldehyde dehydrogenase from PtoDC3000. Site-directed mutants targeting the catalytic residues Cys302 and Glu267 resulted in a loss of enzymatic activity. The X-ray crystal structure of the catalytically inactive AldA C302A mutant in complex with IAA and NAD+ showed the cofactor adopting a conformation that differs from the previously reported structure of AldA. These structures suggest that NAD+ undergoes a conformational change during the AldA reaction mechanism similar to that reported for human ALDH. Site-directed mutagenesis of the IAA binding site indicates that changes in the active site surface reduces AldA activity; however, substitution of Phe169 with a tryptophan altered the substrate selectivity of the mutant to prefer octanal. The present study highlights the inherent biochemical versatility of members of the ALDH enzyme superfamily in P. syringae.

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 The scope of flavin-dependent reactions and processes in the model plant Arabidopsis thaliana

2021 ◽  
Vol 189 ◽  
pp. 112822
Author(s):  
Reinmar Eggers ◽  
Alexandra Jammer ◽  
Shalinee Jha ◽  
Bianca Kerschbaumer ◽  
Majd Lahham ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Model Plant ◽  
Model Plant Arabidopsis Thaliana ◽  
Plant Arabidopsis Thaliana

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.

scholarly journals The Flavoproteome of the Model Plant Arabidopsis thaliana

2020 ◽  
Vol 21 (15) ◽  
pp. 5371 ◽  
Author(s):  
Patrick Schall ◽  
Lucas Marutschke ◽  
Bernhard Grimm
Keyword(s):  
Arabidopsis Thaliana ◽  
Transcriptional Control ◽  
Gene Families ◽  
Flavin Mononucleotide ◽  
Biotic And Abiotic Stress ◽  
Homologous Genes ◽  
Model Plant Arabidopsis Thaliana ◽  
Metabolic Activities ◽  
Flavin Binding ◽  
Plant Arabidopsis Thaliana

Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are essential cofactors for enzymes, which catalyze a broad spectrum of vital reactions. This paper intends to compile all potential FAD/FMN-binding proteins encoded by the genome of Arabidopsis thaliana. Several computational approaches were applied to group the entire flavoproteome according to (i) different catalytic reactions in enzyme classes, (ii) the localization in subcellular compartments, (iii) different protein families and subclasses, and (iv) their classification to structural properties. Subsequently, the physiological significance of several of the larger flavoprotein families was highlighted. It is conclusive that plants, such as Arabidopsis thaliana, use many flavoenzymes for plant-specific and pivotal metabolic activities during development and for signal transduction pathways in response to biotic and abiotic stress. Thereby, often two up to several homologous genes are found encoding proteins with high protein similarity. It is proposed that these gene families for flavoproteins reflect presumably their need for differential transcriptional control or the expression of similar proteins with modified flavin-binding properties or catalytic activities.

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