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 Control of vein-forming, striped gene expression by auxin signaling

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Anmol Krishna ◽  
Jason Gardiner ◽  
Tyler J. Donner ◽  
Enrico Scarpella
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Acetic Acid ◽  
Target Gene ◽  
Target Genes ◽  
Auxin Signaling ◽  
Plant Leaves ◽  
Vein Formation ◽  
Indole 3 Acetic Acid ◽  
Differential Affinity

Abstract Background Activation of gene expression in striped domains is a key building block of biological patterning, from the recursive formation of veins in plant leaves to that of ribs and vertebrae in our bodies. In animals, gene expression is activated in striped domains by the differential affinity of broadly expressed transcription factors for their target genes and the combinatorial interaction between such target genes. In plants, how gene expression is activated in striped domains is instead unknown. We address this question for the broadly expressed MONOPTEROS (MP) transcription factor and its target gene ARABIDOPSIS THALIANA HOMEOBOX FACTOR8 (ATHB8). Results We find that ATHB8 promotes vein formation and that such vein-forming function depends on both levels of ATHB8 expression and width of ATHB8 expression domains. We further find that ATHB8 expression is activated in striped domains by a combination of (1) activation of ATHB8 expression through binding of peak levels of MP to a low-affinity MP-binding site in the ATHB8 promoter and (2) repression of ATHB8 expression by MP target genes of the AUXIN/INDOLE-3-ACETIC-ACID-INDUCIBLE family. Conclusions Our findings suggest that a common regulatory logic controls activation of gene expression in striped domains in both plants and animals despite the independent evolution of their multicellularity.

scholarly journals iac Gene Expression in the Indole-3-Acetic Acid-Degrading Soil Bacterium Enterobacter soli LF7

2018 ◽  
Vol 84 (19) ◽  
Author(s):  
Isaac V. Greenhut ◽  
Beryl L. Slezak ◽  
Johan H. J. Leveau
Keyword(s):  
Gene Expression ◽  
Acetic Acid ◽  
Promoter Region ◽  
Deletion Mutant ◽  
Plant Hormone ◽  
Major Facilitator Superfamily ◽  
Soil Bacterium ◽  
Content Type ◽  
Indole 3 Acetic Acid

ABSTRACT We show for soil bacterium Enterobacter soli LF7 that the possession of an indole-3-acetic acid catabolic (iac) gene cluster is causatively linked to the ability to utilize the plant hormone indole-3-acetic acid (IAA) as a carbon and energy source. Genome-wide transcriptional profiling by mRNA sequencing revealed that these iac genes, chromosomally arranged as iacHABICDEFG and coding for the transformation of IAA to catechol, were the most highly induced (>29-fold) among the relatively few (<1%) differentially expressed genes in response to IAA. Also highly induced and immediately downstream of the iac cluster were genes for a major facilitator superfamily protein (mfs) and enzymes of the β-ketoadipate pathway (pcaIJD-catBCA), which channels catechol into central metabolism. This entire iacHABICDEFG-mfs-pcaIJD-catBCA gene set was constitutively expressed in an iacR deletion mutant, confirming the role of iacR, annotated as coding for a MarR-type regulator and located upstream of iacH, as a repressor of iac gene expression. In E. soli LF7 carrying the DNA region upstream of iacH fused to a promoterless gfp gene, green fluorescence accumulated in response to IAA at concentrations as low as 1.6 μM. The iacH promoter region also responded to chlorinated IAA, but not other aromatics tested, indicating a narrow substrate specificity. In an iacR deletion mutant, gfp expression from the iacH promoter region was constitutive, consistent with the predicted role of iacR as a repressor. A deletion analysis revealed putative −35/−10 promoter sequences upstream of iacH, as well as a possible binding site for the IacR repressor. IMPORTANCE Bacterial iac genes code for the enzymatic conversion of the plant hormone indole-3-acetic acid (IAA) to catechol. Here, we demonstrate that the iac genes of soil bacterium Enterobacter soli LF7 enable growth on IAA by coarrangement and coexpression with a set of pca and cat genes that code for complete conversion of catechol to central metabolites. This work contributes in a number of novel and significant ways to our understanding of iac gene biology in bacteria from (non-)plant environments. More specifically, we show that LF7's response to IAA involves derepression of the MarR-type transcriptional regulator IacR, which is quite fast (less than 25 min upon IAA exposure), highly specific (only in response to IAA and chlorinated IAA, and with few genes other than iac, cat, and pca induced), relatively sensitive (low micromolar range), and seemingly tailored to exploit IAA as a source of carbon and energy.

scholarly journals Control of Vein-Forming, Striped Gene-Expression by Auxin Signaling

2020 ◽  
Author(s):  
Anmol Krishna ◽  
Jason Gardiner ◽  
Tyler J. Donner ◽  
Enrico Scarpella
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Acetic Acid ◽  
Target Gene ◽  
Target Genes ◽  
Auxin Signaling ◽  
Plant Leaves ◽  
Vein Formation ◽  
Indole 3 Acetic Acid ◽  
Differential Affinity

ABSTRACTActivation of gene expression in striped domains is a key building block of biological patterning, from the recursive formation of veins in plant leaves to that of ribs and vertebrae in our bodies. In animals, gene expression is activated in striped domains by the differential affinity of broadly expressed transcription factors for their target genes and the combinatorial interaction between such target genes. In plants, how gene expression is activated in striped domains is instead unknown. We address this question for the broadly expressed MONOPTEROS (MP) transcription factor and its target gene ARABIDOPSIS THALIANA HOMEOBOX FACTOR8 (ATHB8). We find that ATHB8 promotes vein formation and that such vein-forming function depends on both levels of ATHB8 expression and width of ATHB8 expression domains. We further find that ATHB8 expression is activated in striped domains by a combination of (1) activation of ATHB8 expression through binding of peak levels of MP to a low-affinity MP-binding site in the ATHB8 promoter and (2) repression of ATHB8 expression by MP target genes of the INDOLE-3-ACETIC-ACID-INDUCIBLE family such as BODENLOS. Our findings suggest that a common regulatory logic controls activation of gene expression in striped domains in both plants and animals despite the independent evolution of their multicellularity.

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 Analysis of the impact of indole-3-acetic acid (IAA) on gene expression during leaf senescence in Arabidopsis thaliana

2020 ◽  
Vol 26 (4) ◽  
pp. 733-745 ◽  
Author(s):  
Nihal Gören-Sağlam ◽  
Elizabeth Harrison ◽  
Emily Breeze ◽  
Gül Öz ◽  
Vicky Buchanan-Wollaston
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Acetic Acid ◽  
Leaf Senescence ◽  
The Impact ◽  
Indole 3 Acetic Acid

scholarly journals Biochemical and Genetic Bases of Indole-3-Acetic Acid (Auxin Phytohormone) Degradation by the Plant-Growth-Promoting Rhizobacterium Paraburkholderia phytofirmans PsJN

2016 ◽  
Vol 83 (1) ◽  
Author(s):  
Raúl Donoso ◽  
Pablo Leiva-Novoa ◽  
Ana Zúñiga ◽  
Tania Timmermann ◽  
Gonzalo Recabarren-Gajardo ◽  
...  
Keyword(s):  
Energy Source ◽  
Gene Regulation ◽  
Acetic Acid ◽  
Plant Growth ◽  
Plant Hormone ◽  
Content Type ◽  
Gene Functions ◽  
Plant Growth Promoting ◽  
Growth Promoting ◽  
Indole 3 Acetic Acid

ABSTRACT Several bacteria use the plant hormone indole-3-acetic acid (IAA) as a sole carbon and energy source. A cluster of genes (named iac) encoding IAA degradation has been reported in Pseudomonas putida 1290, but the functions of these genes are not completely understood. The plant-growth-promoting rhizobacterium Paraburkholderia phytofirmans PsJN harbors iac gene homologues in its genome, but with a different gene organization and context than those of P. putida 1290. The iac gene functions enable P. phytofirmans to use IAA as a sole carbon and energy source. Employing a heterologous expression system approach, P. phytofirmans iac genes with previously undescribed functions were associated with specific biochemical steps. In addition, two uncharacterized genes, previously unreported in P. putida and found to be related to major facilitator and tautomerase superfamilies, are involved in removal of an IAA metabolite called dioxindole-3-acetate. Similar to the case in strain 1290, IAA degradation proceeds through catechol as intermediate, which is subsequently degraded by ortho-ring cleavage. A putative two-component regulatory system and a LysR-type regulator, which apparently respond to IAA and dioxindole-3-acetate, respectively, are involved in iac gene regulation in P. phytofirmans. These results provide new insights about unknown gene functions and complex regulatory mechanisms in IAA bacterial catabolism. IMPORTANCE This study describes indole-3-acetic acid (auxin phytohormone) degradation in the well-known betaproteobacterium P. phytofirmans PsJN and comprises a complete description of genes, some of them with previously unreported functions, and the general basis of their gene regulation. This work contributes to the understanding of how beneficial bacteria interact with plants, helping them to grow and/or to resist environmental stresses, through a complex set of molecular signals, in this case through degradation of a highly relevant plant hormone.

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.

Determination of Plant Hormone Indole-3-Acetic Acid in Aqueous Solution

2012 ◽  
Vol 25 (1) ◽  
pp. 303-307 ◽  
Author(s):  
Jana Bulíčková ◽  
Romana Sokolová ◽  
Stefania Giannarelli ◽  
Beatrice Muscatello
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Plant Hormone ◽  
Indole 3 Acetic Acid
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