Microbial Plant Hormone Modulation and Its Impact on Plant Growth, Development and Stress Resistance

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Plant Microbe Interactions".

Deadline for manuscript submissions: closed (20 November 2021) | Viewed by 20329

Special Issue Editor


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Guest Editor
iBET, Instituto de Biologia Experimental e Tecnológica, Oeiras, Portugal
Interests: plant-growth-promoting bacteria; plant-microbe interactions; microbial biotechnology; microbial ecology; genomics

Special Issue Information

Dear colleagues,

Plant hormones are major regulators of the developmental, stress resistance, symbiotic, and defense programs of plants. As a result, plant-associated microorganisms have developed intricate mechanisms to modulate plant hormone concentrations and signaling mechanisms. The microbial modulation of plant hormones can occur, i) directly, when microorganisms provide or consume plant hormones, or ii) indirectly, through the production of several molecules/compounds (e.g., effectors, toxins) that impact the plant hormone synthesis and signaling mechanisms.

Understanding the processes involved in microbial plant hormone modulation is, therefore, of extreme importance for the development of novel strategies aiming to maximize plant growth and stress resistance and to improve several key agricultural and biotechnological applications.

This Special Issue invites original research papers and reviews that cover all aspects of plant–microbe interaction research focusing on plant hormone modulation, including the following:

  1. Studies on bacterial, fungal, and other microorganisms’ plant hormone biosynthesis, catabolism, and regulation processes;
  2. The modulation of plant hormones and their signaling components by symbionts (e.g., rhizobia, mycorrhiza), mutualists (plant-growth-promoting microorganisms), and pathogens.
  3. The impact of plant hormone modulation in plant microbiome assembly, and microorganisms’ colonization processes.
  4. The effects of microbial plant hormone modulation and its role in plant biotic and abiotic stress resistance.

Dr. Francisco Xavier Nascimento
Guest Editor

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Keywords

  • microbial plant hormone
  • microbial modulation
  • plant-microbe interactions
  • rhizobia
  • mycorrhiza

Published Papers (5 papers)

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Research

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17 pages, 4185 KiB  
Article
Molecular and Biochemical Characterization, Antimicrobial Activity, Stress Tolerance, and Plant Growth-Promoting Effect of Endophytic Bacteria Isolated from Wheat Varieties
by Dawood Shah, Mohammad Sayyar Khan, Shahkaar Aziz, Haidar Ali and Lorenzo Pecoraro
Microorganisms 2022, 10(1), 21; https://doi.org/10.3390/microorganisms10010021 - 23 Dec 2021
Cited by 26 | Viewed by 6115
Abstract
Endophytic bacteria have been utilized as an alternative source to chemical fertilizers and pesticides to enhance plant productivity and defense mechanisms against biotic and abiotic stress. Five endophytic bacterial strains were isolated from the seeds of three different Pakistani wheat varieties (Ghaneemat-e-IBGE, Atta-Habib, [...] Read more.
Endophytic bacteria have been utilized as an alternative source to chemical fertilizers and pesticides to enhance plant productivity and defense mechanisms against biotic and abiotic stress. Five endophytic bacterial strains were isolated from the seeds of three different Pakistani wheat varieties (Ghaneemat-e-IBGE, Atta-Habib, and Siren). The isolated strains AH-1, S-5, S-7, GI-1, and GI-6 showed phylogenetic similarity with Bacillus altitudinis, B. aryabhattai, B. wiedmannii, Pseudomonas aeruginosa, and Burkholderia gladioli, respectively. All strains showed catalase activity (except AH-1) and Indole-3-acetic acid production, with the highest concentration (16.77 μg·mL−1) found for GI-6, followed by S-5 (11.5 μg·mL−1), nitrogen assimilation (except S-7), phosphorus solubilization (except S-7 and AH-1), and ability to produce siderophores, with maximum productions for GI-6 (31 ± 3.5 psu) and GI-1 (30 ± 2.9 psu). All five analyzed strains possessed antimicrobial activity, which was particularly strong in GI-6 and S-5 against Klebsiella pneumonia, Escherichia coli, and Bacillus subtilis. Increasing salinity stress with NaCl negatively affected the bacterial growth of all isolates. However, strains GI-6 and S-5 showed salt tolerance after three days of incubation. A drought tolerance test resulted in a negative impact of poly ethylene glycol on bacterial growth, which was, however, less pronounced in GI-6 strain. The GI-6 strain revealed growth-promoting effects on inoculated wheat plants. Full article
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21 pages, 22487 KiB  
Article
The Nexus between Fire and Soil Bacterial Diversity in the African Miombo Woodlands of Niassa Special Reserve, Mozambique
by Ivete Sandra Alberto Maquia, Paula Fareleira, Isabel Videira e. Castro, Ricardo Soares, Denise R. A. Brito, Aires Afonso Mbanze, Aniceto Chaúque, Cristina Máguas, Obinna T. Ezeokoli, Natasha Sofia Ribeiro, Isabel Marques and Ana I. Ribeiro-Barros
Microorganisms 2021, 9(8), 1562; https://doi.org/10.3390/microorganisms9081562 - 22 Jul 2021
Cited by 7 | Viewed by 3253
Abstract
(1) Background: the Miombo woodlands comprise the most important vegetation from southern Africa and are dominated by tree legumes with an ecology highly driven by fires. Here, we report on the characterization of bacterial communities from the rhizosphere of Brachystegia boehmii in different [...] Read more.
(1) Background: the Miombo woodlands comprise the most important vegetation from southern Africa and are dominated by tree legumes with an ecology highly driven by fires. Here, we report on the characterization of bacterial communities from the rhizosphere of Brachystegia boehmii in different soil types from areas subjected to different regimes. (2) Methods: bacterial communities were identified through Illumina MiSeq sequencing (16S rRNA). Vigna unguiculata was used as a trap to capture nitrogen-fixing bacteria and culture-dependent methods in selective media were used to isolate plant growth promoting bacteria (PGPB). PGP traits were analysed and molecular taxonomy of the purified isolates was performed. (3) Results: Bacterial communities in the Miombo rhizosphere are highly diverse and driven by soil type and fire regime. Independent of the soil or fire regime, the functional diversity was high, and the different consortia maintained the general functions. A diverse pool of diazotrophs was isolated, and included symbiotic (e.g., Mesorhizobium sp., Neorhizobium galegae, Rhizobium sp., and Ensifer adhaerens), and non-symbiotic (e.g., Agrobacterium sp., Burkholderia sp., Cohnella sp., Microvirga sp., Pseudomonas sp., and Stenotrophomonas sp.) bacteria. Several isolates presented cumulative PGP traits. (4) Conclusions: Although the dynamics of bacterial communities from the Miombo rhizosphere is driven by fire, the maintenance of high levels of diversity and functions remain unchanged, constituting a source of promising bacteria in terms of plant-beneficial activities such as mobilization and acquisition of nutrients, mitigation of abiotic stress, and modulation of plant hormone levels. Full article
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14 pages, 2132 KiB  
Article
Caenorhabditis elegans Extracts Stimulate IAA Biosynthesis in Arthrobacter pascens ZZ21 via the Indole-3-pyruvic Acid Pathway
by Mengsha Li, Teng Li, Ming Zhou, Mengdi Li, Yexin Zhao, Jingjing Xu, Feng Hu and Huixin Li
Microorganisms 2021, 9(5), 970; https://doi.org/10.3390/microorganisms9050970 - 30 Apr 2021
Cited by 4 | Viewed by 2689
Abstract
Inter-organismal metabolites play important roles in regulating organism behavior and the communication between organisms. Nematodes, the most abundant animals on earth, are crucial participants in soil ecosystems through their interactions with microbes. For example, bacterial-feeding nematodes increase the activity of indole-3-acetic acid (IAA)-producing [...] Read more.
Inter-organismal metabolites play important roles in regulating organism behavior and the communication between organisms. Nematodes, the most abundant animals on earth, are crucial participants in soil ecosystems through their interactions with microbes. For example, bacterial-feeding nematodes increase the activity of indole-3-acetic acid (IAA)-producing bacteria and the IAA content in soil. However, the way in which these nematodes interact with bacteria and affect IAA biosynthesis is not well understood. Here, using the model nematode Caenorhabditis elegans and the plant-beneficial bacterium Arthrobacter pascens ZZ21, we examined the effects of nematode excretions or extracts on bacterial IAA biosynthesis. To explore the underlying regulatory mechanism in more detail, we performed transcriptome sequencing and metabolomic analysis. Our findings suggest that C. elegans extracts promote IAA biosynthesis in A. pascens ZZ21 by increasing the expression of genes and the abundance of intermediates involved in the indole-3-pyruvic acid (IPyA) pathway. C. elegans extracts also significantly influenced biosynthetic and metabolic activity in A. pascens ZZ21. Treatment with C. elegans extracts promoted pyruvate metabolism, the citrate cycle (TCA) cycle and the production of some TCA-cycle-related amino acids and inhibited oxidative phosphorylation, which induced the accumulation of reduced nicotinamide adenine dinucleotide (NADH). We propose that the extracts altered the metabolism of A. pascens ZZ21 to help the bacteria resist stress caused by their predator. Our findings indicate that bacterial-feeding nematodes mediate the interaction between nematodes and bacteria via their extracts, providing insights into the ecological function of C. elegans in soil. Full article
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Review

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15 pages, 1387 KiB  
Review
Pseudomonas 1-Aminocyclopropane-1-carboxylate (ACC) Deaminase and Its Role in Beneficial Plant-Microbe Interactions
by Bernard R. Glick and Francisco X. Nascimento
Microorganisms 2021, 9(12), 2467; https://doi.org/10.3390/microorganisms9122467 - 29 Nov 2021
Cited by 22 | Viewed by 2985
Abstract
The expression of the enzyme 1-aminocylopropane-1-carboxylate (ACC) deaminase, and the consequent modulation of plant ACC and ethylene concentrations, is one of the most important features of plant-associated bacteria. By decreasing plant ACC and ethylene concentrations, ACC deaminase-producing bacteria can overcome some of the [...] Read more.
The expression of the enzyme 1-aminocylopropane-1-carboxylate (ACC) deaminase, and the consequent modulation of plant ACC and ethylene concentrations, is one of the most important features of plant-associated bacteria. By decreasing plant ACC and ethylene concentrations, ACC deaminase-producing bacteria can overcome some of the deleterious effects of inhibitory levels of ACC and ethylene in various aspects of plant-microbe interactions, as well as plant growth and development (especially under stressful conditions). As a result, the acdS gene, encoding ACC deaminase, is often prevalent and positively selected in the microbiome of plants. Several members of the genus Pseudomonas are widely prevalent in the microbiome of plants worldwide. Due to its adaptation to a plant-associated lifestyle many Pseudomonas strains are of great interest for the development of novel sustainable agricultural and biotechnological solutions, especially those presenting ACC deaminase activity. This manuscript discusses several aspects of ACC deaminase and its role in the increased plant growth promotion, plant protection against abiotic and biotic stress and promotion of the rhizobial nodulation process by Pseudomonas. Knowledge regarding the properties and actions of ACC deaminase-producing Pseudomonas is key for a better understanding of plant-microbe interactions and the selection of highly effective strains for various applications in agriculture and biotechnology. Full article
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19 pages, 8515 KiB  
Review
Biochemical and Structural Aspects of Cytokinin Biosynthesis and Degradation in Bacteria
by Jitka Frébortová and Ivo Frébort
Microorganisms 2021, 9(6), 1314; https://doi.org/10.3390/microorganisms9061314 - 16 Jun 2021
Cited by 22 | Viewed by 4157
Abstract
It has been known for quite some time that cytokinins, hormones typical of plants, are also produced and metabolized in bacteria. Most bacteria can only form the tRNA-bound cytokinins, but there are examples of plant-associated bacteria, both pathogenic and beneficial, that actively synthesize [...] Read more.
It has been known for quite some time that cytokinins, hormones typical of plants, are also produced and metabolized in bacteria. Most bacteria can only form the tRNA-bound cytokinins, but there are examples of plant-associated bacteria, both pathogenic and beneficial, that actively synthesize cytokinins to interact with their host. Similar to plants, bacteria produce diverse cytokinin metabolites, employing corresponding metabolic pathways. The identification of genes encoding the enzymes involved in cytokinin biosynthesis and metabolism facilitated their detailed characterization based on both classical enzyme assays and structural approaches. This review summarizes the present knowledge on key enzymes involved in cytokinin biosynthesis, modifications, and degradation in bacteria, and discusses their catalytic properties in relation to the presence of specific amino acid residues and protein structure. Full article
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