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Lee CY, Harper CP, Lee SG, Qi Y, Clay T, Aoi Y, Jez JM, Kasahara H, Blodgett JAV, Kunkel BN. Investigating the biosynthesis and roles of the auxin phenylacetic acid during Pseudomonas syringae- Arabidopsis thaliana pathogenesis. FRONTIERS IN PLANT SCIENCE 2024; 15:1408833. [PMID: 39091312 PMCID: PMC11291249 DOI: 10.3389/fpls.2024.1408833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 07/02/2024] [Indexed: 08/04/2024]
Abstract
Several plant-associated microbes synthesize the auxinic plant growth regulator phenylacetic acid (PAA) in culture; however, the role of PAA in plant-pathogen interactions is not well understood. In this study, we investigated the role of PAA during interactions between the phytopathogenic bacterium Pseudomonas syringae strain PtoDC3000 (PtoDC3000) and the model plant host, Arabidopsis thaliana. Previous work demonstrated that indole-3-acetaldehyde dehydrogenase A (AldA) of PtoDC3000 converts indole-3-acetaldehyde (IAAld) to the auxin indole-3-acetic acid (IAA). Here, we further demonstrated the biochemical versatility of AldA by conducting substrate screening and steady-state kinetic analyses, and showed that AldA can use both IAAld and phenylacetaldehyde as substrates to produce IAA and PAA, respectively. Quantification of auxin in infected plant tissue showed that AldA-dependent synthesis of either IAA or PAA by PtoDC3000 does not contribute significantly to the increase in auxin levels in infected A. thaliana leaves. Using available arogenate dehydratase (adt) mutant lines of A. thaliana compromised for PAA synthesis, we observed that a reduction in PAA-Asp and PAA-Glu is correlated with elevated levels of IAA and increased susceptibility. These results provide evidence that PAA/IAA homeostasis in A. thaliana influences the outcome of plant-microbial interactions.
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Affiliation(s)
- Chia-Yun Lee
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Christopher P. Harper
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Soon Goo Lee
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA, United States
| | - Yunci Qi
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
- United States Department of Agriculture-Agricultural Research Service, New Orleans, LA, United States
| | - Taylor Clay
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA, United States
| | - Yuki Aoi
- Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan
| | - Joseph M. Jez
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Hiroyuki Kasahara
- Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Joshua A. V. Blodgett
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Barbara N. Kunkel
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
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Double agent indole-3-acetic acid (IAA): Mechanistic analysis of indole-3-acetaldehyde dehydrogenase AldA that synthesizes IAA, an auxin that aids bacterial virulence. Biosci Rep 2021; 41:229488. [PMID: 34369556 PMCID: PMC8385190 DOI: 10.1042/bsr20210598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 07/10/2021] [Accepted: 07/30/2021] [Indexed: 11/17/2022] Open
Abstract
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 nicotinamide adenine dinucleotide (NAD+) (Bioscience Reports (2020) 40(12), https://doi.org/10.1042/BSR20202959). Using mutagenesis, enzyme kinetics, and structural analysis, Zhang et al. established 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-catalyzed reactions, and further show that the key active site residues control substrate specificity. We also contemplate that insights from the present study can be used to engineer novel ALDH enzymes for environmental, health, and industrial applications.
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Investigating the reaction and substrate preference of indole-3-acetaldehyde dehydrogenase from the plant pathogen Pseudomonas syringae PtoDC3000. Biosci Rep 2021; 40:227102. [PMID: 33325526 PMCID: PMC7745063 DOI: 10.1042/bsr20202959] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/24/2020] [Accepted: 12/01/2020] [Indexed: 12/14/2022] Open
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.
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Tola AJ, Jaballi A, Germain H, Missihoun TD. Recent Development on Plant Aldehyde Dehydrogenase Enzymes and Their Functions in Plant Development and Stress Signaling. Genes (Basel) 2020; 12:genes12010051. [PMID: 33396326 PMCID: PMC7823795 DOI: 10.3390/genes12010051] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 12/24/2020] [Accepted: 12/28/2020] [Indexed: 12/15/2022] Open
Abstract
Abiotic and biotic stresses induce the formation of reactive oxygen species (ROS), which subsequently causes the excessive accumulation of aldehydes in cells. Stress-derived aldehydes are commonly designated as reactive electrophile species (RES) as a result of the presence of an electrophilic α, β-unsaturated carbonyl group. Aldehyde dehydrogenases (ALDHs) are NAD(P)+-dependent enzymes that metabolize a wide range of endogenous and exogenous aliphatic and aromatic aldehyde molecules by oxidizing them to their corresponding carboxylic acids. The ALDH enzymes are found in nearly all organisms, and plants contain fourteen ALDH protein families. In this review, we performed a critical analysis of the research reports over the last decade on plant ALDHs. Newly discovered roles for these enzymes in metabolism, signaling and development have been highlighted and discussed. We concluded with suggestions for future investigations to exploit the potential of these enzymes in biotechnology and to improve our current knowledge about these enzymes in gene signaling and plant development.
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