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Transverse sections of roots of glasshouse-grown rice seedlings. (a) Light micrograph of cv. Moroberekan at 10 d after inoculation (DAI) by Herbaspirillum seropedicae Z67-gusA. Bacteria are visible on the root surface (arrows), but few are visible within the root tissues. A, aerenchyma; S, stele. Bar, 20 µm. (b) Light micrograph of an uninoculated root of cv. Moroberekan with a wound/break in the epidermis (asterisk). Note the bacteria within the wound (large arrows) and on the root surface (small arrows). A, Aerenchyma, S, stele. Bar, 20 µm. (c) Light micrograph of cv. IR45 at 10 DAI by H. seropedicae Z67-gusA. Few bacteria are visible, but fungal hyphae can be seen within many of the cortical and aerenchyma cells (arrows). A, aerenchyma; S, stele. Bar, 20 µm. (d) Transmission electron micrograph of cortical cell in (c). This section was immunogold labelled with an antibody raised against H. seropedicae Z67 followed by 15 nm goat anti-rabbit gold. Note the immunogold labelled bacteria (arrows) adjacent to a fungal hypha (asterisk). W, cell wall. Bar, 200 nm.
Source publication
Varieties of rice (Oryza sativa) differing in tolerance to aluminium (Al) were
evaluated for their N-fixation ability after inoculation with a gusA-marked strain of
Herbaspirillum seropedicae Z67.
* Under axenic conditions, by 30 d, inoculation resulted in enhanced nitrogenase
activity, d. wt, total N and total C content only in the Al-tolerant var...
Contexts in source publication
Context 1
... 10 DAT, H. seropedicae Z67-gusA could be localized on both the roots and shoots of glasshouse-grown rice plants using GUS staining (Fig. 1c,d). Light microscopy of sections of roots (both inoculated and uninoculated) showed that there were large numbers of unidentified bacteria on the surfaces of both varieties (Fig. 6a,b), as well as some within the roots, particularly where there were wounds or breaks in the epidermis (Fig. 6b). Some, but not all of these bacteria were immunogold labelled with an antibody raised against H. seropedicae (not shown). A consistent feature of the roots of cv. IR45 were fungal hyphae within the cortical cells (Fig. 6c) and ...
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... of glasshouse-grown rice plants using GUS staining (Fig. 1c,d). Light microscopy of sections of roots (both inoculated and uninoculated) showed that there were large numbers of unidentified bacteria on the surfaces of both varieties (Fig. 6a,b), as well as some within the roots, particularly where there were wounds or breaks in the epidermis (Fig. 6b). Some, but not all of these bacteria were immunogold labelled with an antibody raised against H. seropedicae (not shown). A consistent feature of the roots of cv. IR45 were fungal hyphae within the cortical cells (Fig. 6c) and more detailed studies using transmission electron microscopy combined with immunogold labelling showed H. ...
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... both varieties (Fig. 6a,b), as well as some within the roots, particularly where there were wounds or breaks in the epidermis (Fig. 6b). Some, but not all of these bacteria were immunogold labelled with an antibody raised against H. seropedicae (not shown). A consistent feature of the roots of cv. IR45 were fungal hyphae within the cortical cells (Fig. 6c) and more detailed studies using transmission electron microscopy combined with immunogold labelling showed H. seropedicae associated with these (Fig. 6d). As suggested by the GUS staining and plate counts, at 10 DAI there was a substantial population of herbaspirilla on the leaf surfaces. 13) and cv. Moroberekan (lanes 14 -25); lanes ...
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... of these bacteria were immunogold labelled with an antibody raised against H. seropedicae (not shown). A consistent feature of the roots of cv. IR45 were fungal hyphae within the cortical cells (Fig. 6c) and more detailed studies using transmission electron microscopy combined with immunogold labelling showed H. seropedicae associated with these (Fig. 6d). As suggested by the GUS staining and plate counts, at 10 DAI there was a substantial population of herbaspirilla on the leaf surfaces. 13) and cv. Moroberekan (lanes 14 -25); lanes 2-4, strains isolated from root surfaces at 10 DAT; lanes 5 -7, strains isolated from surface-sterilized roots at 10 DAT; lanes 8 -10, strains isolated ...
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... the addition of chloramphenicol was essential in localizing the GUS activity of the inoculated bacteria, as it inhibits the induction of GUS activity by the indigenous bacteria ( Wilson et al., 1995), which are abundant on and in glasshouse-grown plants. The GUS staining suggested that the herbaspirilla were localized on the surfaces of both roots and aerial parts, and this was confirmed using sections for light microscopy and TEM (Figs 6 and 7). The latter not only showed that the bacteria were present on root surfaces, but also that they were within leaf intercellular spaces and mesophyll cells. ...
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... latter not only showed that the bacteria were present on root surfaces, but also that they were within leaf intercellular spaces and mesophyll cells. This pattern of localization was similar to that shown for the axenically grown plants, but the herbaspirilla were much more difficult to find within the glasshouse-grown plants, particularly as there were numerous unidentified microorganisms present (Figs 6 and 7). Therefore, immunogold labelling with an antibody specific to H. seropedicae was essential in recognizing these bacteria under the TEM. ...
Citations
... Among the genera of PGPB that establish efficient associations with different crop species, Herbaspirillum stands out as a model to study the processes of bacterial recognition, colonization, and growth promotion in grasses, being recommended as maize inoculant (Reis et al., 2010). Herbaspirillum seropedicae is an endophytic bproteobacteria found naturally associating with several economically important grasses such as sugarcane, wheat, rice, and maize, increasing crop productivity (Baldani et al., 1986;Olivares et al., 1996;Gyaneshwar et al., 2002;Monteiro et al., 2008). Despite being frequently found in the rhizosphere, endophytic colonization by H. seropedicae is based on the attachment of the bacteria to root surfaces and the subsequent colonization of the emergence points of lateral roots . ...
The interactions between plants, beneficial bacteria and their environment are profoundly shaped by various environmental factors, including light, temperature, water availability, and soil quality. Despite efforts to elucidate the molecular mechanisms involved in the association between plants and beneficial bacteria, like Plant Growth-Promoting Bacteria (PGPB), with many studies focusing on the transcriptional reprogramming in the plant, there is no report on the modulation of genetic controls from both plant and associated bacteria standpoints, in response to environment. The main goal of this study was to investigate the relationship between plant-bacteria-environment signaling, using as a model maize plants inoculated with H. seropedicae ZAE94 and cultivated with different doses of N (0.3 and 3 mM). For this purpose, we performed rRNA-depleted RNA-seq to determine the global gene expression of both maize roots and associated H. seropedicae ZAE94. Our results revealed a differential modulation of maize nitrogen metabolism, phytohormone and cell wall responses when associated with H. seropedicae ZAE94 at different N concentrations. In parallel, a modulation of the bacterial metabolism could be observed, by regulating genes involved in transport, secretion system, cell mobility, oxidoreductases, and chemotaxis, when bacteria were associated with maize roots and cultivated at different doses of N. The molecular and phenotypic data of maize plantlets suggested that different doses of N fertilization differentially regulated the beneficial effects of bacterial inoculation, as higher doses (3 mM) favored shoot elongation and lower doses (0.3 mM) favored increase in plant biomass. Our results provide a valuable integrated overview of differentially expressed genes in both maize and associated H. seropedicae ZAE94 in response to different N availability, revealing new insights into pathways involved in grass-PGPB associations.
... Se empleó la cepa Herbaspirillum seropedicae Z67 como control positivo del ensayo. (30,31) Se emplearon 30 plantas por tratamiento. ...
Introducción:
El desarrollo de bioproductos para beneficiar cultivos de importancia económica como el arroz tributa directamente a nuestra soberanía alimentaria. El objetivo del trabajo fue obtener y caracterizar cepas bacterianas asociadas a 2 cultivares de arroz de amplia distribución en Cuba, en cuanto a sus potencialidades como bacterias promotoras del crecimiento vegetal.
Métodos:
Se realizó el aislamiento de bacterias asociadas a la rizosfera y semillas de los cultivares de arroz INCA LP-5 e INCA LP-7 y se identificaron por secuenciación parcial del ARNr 16S. Las cepas se caracterizaron en cuanto a potencialidades como biofertilizantes, fitoestimulantes, de biocontrol y atributos de infección y colonización. Se estudió la capacidad endofítica de una cepa de Rhizobium en plántulas de arroz, a partir de ensayos de inoculación y microscopía confocal de fluorescencia. Se desarrollaron experimentos de inoculación en condiciones controladas, semicontroladas y de campo.
Resultados:
Se aislaron 43 cepas; 24 de la rizosfera y 19 del interior de semillas de arroz y se identificaron 8 géneros bacterianos asociados: Rhizobium, Pantoea, Pseudomonas, Acinetobacter, Mitsuaria, Enterobacter, Bacillus y Paenibacillus. Algunas cepas solubilizaron fosfato de calcio y potasio, crecieron en medios libres de nitrógeno y produjeron sideróforos, compuestos indólicos, enzimas hidrolíticas y formaron biopelículas. Se comprobó la capacidad endofítica de una cepa de Rhizobium y su colonización sistémica en plántulas de arroz. La inoculación de algunas cepas incrementó el contenido de nutrientes, algunas biomoléculas y el crecimiento de plantas de arroz. Además, el rendimiento del cultivo se favoreció entre 30 % y 80 %, con la reducción del 40 % a 60 % de la fertilización nitrogenada. Conclusiones, la investigación constituye un aporte al conocimiento de la interacción Rhizobium-arroz y a la identificación, caracterización y selección de cepas bacterianas con potencialidades para el desarrollo de bioproductos que impacten positivamente en el medio ambiente, la economía y la sociedad.
... The poor market share of PGPB-based biofertilizers is caused by a variety of problems [92]. Although a diverse community of PGPB has been identified with versatile growth-promoting characteristics, very few PGPB are successfully registered for commercial use [93,94] due to inconsistent results in greenhouse/nursery, and field-level experiments [95] (Figs. 3 and 4). This review seeks to identify the obstacles that prevent PGPB from being registered as potentially effective, reliable, and safe biofertilizers, and appropriate strategies to overcome the challenges to mitigate global crop loss in an environment-friendly manner. ...
Zero hunger is a significant sustainable development goal to ensure food access by all people in vulnerable situations by 2030. However, climate change-mediated possible threats (drought, salinity, and submergence) are adversely impacting our crop yield, which would eventually jeopardize our ability to feed ourselves. Pathogenic attacks caused by nematodes, fungi, bacteria, and viruses are examples of biotic stresses that also result in lower food yields for human consumption. Despite the immense potential for plant growth-promoting bacteria (PGPB) to reduce biotic and abiotic stressors, very few PGPB have been effectively registered as biofertilizers in the commercial sector. The biofertilizer market share includes a tiny fraction of the synthetic agrochemical market share. Specific obstacles hamper field-level applications of PGPB that were effective in laboratories. The preparation of formulations faces numerous difficulties, including issues with shelf life, viability upkeep, biofilm formation, and risks to human health. Different regions have different weather patterns and soil compositions. The full image of microbial interactions is still largely unknown. This review aims to explore the recent advancements in biofertilizer formulations and their in vivomonitoring techniques to correlate with the mitigation of the obstacles. At the same time, possible ways for creating effective, reliable, and affordable PGPB formulations are also discussed.
... Through these findings, all the microbial inoculants increased the growth and nutritional assimilation (total N) of oil palm plantlets and at the same time also improved soil properties. Not only in oil palm plantlets, studies also showed that H. seropedicae can fix the significant amount of N 2 and contribute to plant growth in sugarcane, rice, and oil palm (Boddey et al., 1995;Elbeltagy et al., 2001;Gyaneshwar et al., 2002;James et al., 2002;Roncato-Maccari et al., 2003;Ai'shah et al., 2009). ...
Continuous discovery of novel in vitro plant culture practices is always essential to promote better plant growth in the shortest possible cultivation period. An alternative approach to conventional micropropagation practice could be achieved through biotization by inoculating selected Plant Growth Promoting Rhizobacteria (PGPR) into the plant tissue culture materials (e.g., callus, embryogenic callus, and plantlets). Such biotization process often allows the selected PGPR to form a sustaining population with various stages of in vitro plant tissues. During the biotization process, plant tissue culture material imposes developmental and metabolic changes and enhances its tolerance to abiotic and biotic stresses, thereby reducing mortality in the acclimatization and pre-nursery stages. Understanding the mechanisms is, therefore crucial for gaining insights into in vitro plant-microbe interactions. Studies of biochemical activities and compound identifications are always essential to evaluate in vitro plant-microbe interactions. Given the importance of biotization in promoting in vitro plant material growth, this review aims to provide a brief overview of the in vitro oil palm plant-microbe symbiosis system.
... The prediction of microbial functions associated in NI and I roots pointed to an early imprinting of H. seropedicae on microbiota functionality. Higher biological N xation capacity in I roots may be attributable to the diazotrophic nature of H. seropedicae, which is known to contain the nifH gene and has been shown to x N in different cereal species, including rice, sorghum, maize and wheat [29,30,31]. However, Pseudomonadota members promoted by H. seropedicae inoculation also contain numerous important intracellular mutualists that may equally contribute to boost N metabolism in planta. ...
Exploiting the beneficial features of the plant microbiota is a promising approach to improve cereal growth and health in a more sustainable manner. Seed-borne endophytic microbiota can intimately colonize the plant’s endosphere and influence plant responses efficiently. Understanding their structure and functions is a critical step towards the formulation of microbial inoculants that can promote plant-beneficial microbiota functions. In this study, both 16S and ITS metabarcoding analyses were employed to explore the structure of the endophytic seed-borne microbiota in wheat seeds as well as in roots either non-inoculated or inoculated with the endophytic bacterium Herbaspirillum seropedicae RAM10. Furthermore, machine learning tools were employed to predict the ecological functions associated to these structural shifts. Inoculation with H. seropedicae markedly changed the composition of the seed-borne endophytic community. This compositional shift mirrored a predicted functional diversification, which was manifested by the differential enrichment of OTUs involved in bacterial nitrogen fixation, nitrate metabolism and aerobic chemoheterotrophy as well as by changes in fungal life strategies. These results suggest that endophytic inoculants could represent suitable vehicles to effectively promote desired plant traits through the modulation of the wheat seed-borne microbiota in the root endosphere.
... Positive results have been documented with the associations between lodgepole pine (Pinus contorta) and Pseudomonas spp. [49]; poplar (Populus trichocarpa) and various endophytes [50]; sugarcane (Saccharum officinarum) and Acetobacter diazotrophicus [51]; wheat (Triticum aestivum) and Klebsiella pneumoniae [52]; rice (Oryza sativa) and Herbaspirillum seropedicae [53,54]; and Setaria viridis and Azospirillum brasilense [55]. ...
In this literature review, we discuss the various functions of beneficial plant bacteria in improving plant nutrition, the defense against biotic and abiotic stress, and hormonal regulation. We also review the recent research on rhizophagy, a nutrient scavenging mechanism in which bacteria enter and exit root cells on a cyclical basis. These concepts are covered in the contexts of soil agriculture and controlled environment agriculture, and they are also used in vertical farming systems. Vertical farming-its advantages and disadvantages over soil agriculture, and the various climatic factors in controlled environment agriculture-is also discussed in relation to plant-bacterial relationships. The different factors under grower control, such as choice of substrate, oxygenation rates, temperature, light, and CO 2 supplementation, may influence plant-bacterial interactions in unintended ways. Understanding the specific effects of these environmental factors may inform the best cultural practices and further elucidate the mechanisms by which beneficial bacteria promote plant growth.
... Various techniques can detect PGPR. These include reporter genes, immuno-based or nucleic acid techniques (13)(14)(15). Nucleic acid-based methods take advantage of unique regions in the DNA sequence of the bacteria of interest to differentiate them from other bacteria abundant in soil. Among the nucleic acid techniques, the Randomly Amplified Polymorphic DNA technique (RAPD) has advantages, as it does not require prior knowledge about the genomic sequence and does not lead to the production of genetically modified organisms; unlike reporter-gene-based techniques. ...
Background and purpose: Synthetic fertilizers damage the environment. Biofertilizers that consist of microorganisms emerge as an environmentally friendly alternative. Biofertilizers improve plant growth by mobilizing soil nutrients, triggering plant hormone synthesis, or competing with pathogenic bacteria. However, biofertilizers often fail due to insufficient colonization of the plant roots.Materials and methods: To explore the colonization dynamics of a bacterial strain commonly used in biofertilizers, Bacillus subtilis OSU-142 (OSU-142), developing a set of primers specific to OSU-142 was aimed. Since its genome is unknown, to identify genomic regions unique to OSU-142 strain, DNAs of more than 40 bacterial strains were fingerprinted, most of which belong to Bacillus subtilis using the Randomly Amplified Polymorphic DNA (RAPD) method.Results: This approach identified a polymorphic band at 880 bp, which was then cloned and sequenced. The sequence showed no perfect match to any known sequences in the tested genomic databases indicating that the region of OSU-142 DNA is highly unique. The primer was converted to Sequence-Characterized Amplified Region (SCAR) primers, and its functionality in detecting OSU-142 genome was confirmed. Newly designed primer set can specifically detect OSU-142.Conclusions: These primers can be useful for basic science or commercial applications on tracking OSU-142 in various environments, thus contributing to biofertilizers’ adoption in the long run.
... Herbaspirillum strains have genomic potential to fix nitrogen, reduce nitrite, and produce siderophores [70]. Herbaspirillum strains also produce plant growth hormones-such as gibberellins and indole acetic acid [71]-and have been shown to promote rice, corn, and sugarcane growth [72]. The other core Burkholderiales OTU (family Comamonadaceae) shared 100% sequence identity with sequences deriving from the genus Delftia. ...
Phaeocystis is a cosmopolitan, bloom-forming phytoplankton genus that contributes significantly to global carbon and sulfur cycles. During blooms, Phaeocystis species produce large carbon-rich colonies, creating a unique interface for bacterial interactions. While bacteria are known to interact with phytoplankton—e.g., they promote growth by producing phytohormones and vitamins—such interactions have not been shown for Phaeocystis. Therefore, we investigated the composition and function of P. globosa microbiomes. Specifically, we tested whether microbiome compositions are consistent across individual colonies from four P. globosa strains, whether similar microbiomes are re-recruited after antibiotic treatment, and how microbiomes affect P. globosa growth under limiting conditions. Results illuminated a core colonial P. globosa microbiome—including bacteria from the orders Alteromonadales, Burkholderiales, and Rhizobiales—that was re-recruited after microbiome disruption. Consistent microbiome composition and recruitment is indicative that P. globosa microbiomes are stable-state systems undergoing deterministic community assembly and suggests there are specific, beneficial interactions between Phaeocystis and bacteria. Growth experiments with axenic and nonaxenic cultures demonstrated that microbiomes allowed continued growth when B-vitamins were withheld, but that microbiomes accelerated culture collapse when nitrogen was withheld. In sum, this study reveals symbiotic and opportunistic interactions between Phaeocystis colonies and microbiome bacteria that could influence large-scale phytoplankton bloom dynamics and biogeochemical cycles.
... Herbaspirillum seropedicae is a well-known PGPB that colonizes and benefits non-legume plants such as rice, sorghum, sugarcane, and maize [14][15][16][17][18] . Past studies have shown that different strains (e.g., B501, Z67) of H. seropedicae can promote plant growth via nitrogen fixation 15,[19][20][21] . ...
... Herbaspirillum seropedicae is a well-known PGPB that colonizes and benefits non-legume plants such as rice, sorghum, sugarcane, and maize [14][15][16][17][18] . Past studies have shown that different strains (e.g., B501, Z67) of H. seropedicae can promote plant growth via nitrogen fixation 15,[19][20][21] . In the current study, we used the same experimental conditions from our previous study in A. brasilense 13 to determine if H. seropedicae B501 could colonize rice roots and promote growth. ...
Non-legume plants such as rice and maize can form beneficial associations with plant growth-promoting bacteria (PGPB) such as Herbaspirillum seropedicae and Azospirillum brasilense. Several studies have shown that these PGPB promote plant growth via multiple mechanisms. Our current understanding of the molecular aspects and signaling between plants like rice and PGPB like Herbaspirillum seropedicae is limited. In this study, we used an experimental system where H. seropedicae could colonize the plant roots and promote growth in wild-type rice. Using this experimental setup, we identified 1688 differentially expressed genes (DEGs) in rice roots, 1 day post-inoculation (dpi) with H. seropedicae. Several of these DEGs encode proteins involved in the flavonoid biosynthetic pathway, defense, hormone signaling pathways, and nitrate and sugar transport. We validated the expression pattern of some genes via RT-PCR. Next, we compared the DEGs identified in this study to those we previously identified in rice roots during associations with another PGPB, Azospirillum brasilense. We identified 628 genes that were differentially expressed during both associations. The expression pattern of these genes suggests that some of these are likely to play a significant role(s) during associations with both H. seropedicae and A. brasilense and are excellent targets for future studies.
... are found in roots, stems, and leaves of many plants, most without disease symptoms (Roncato-Maccari et al., 2003), and can promote the growth of Poaceae (maize, Michantus, rice, sorghum, and sugarcane; Monteiro et al., 2012). Specifically, H. seropedicae increased growth and nitrogen accumulation in rice varieties (Divan-Baldani et al., 2000;Gyaneshwar et al., 2002;Roncato-Maccari et al., 2003;Trovero et al., 2018). In light of the variable plant growth-promoting rhizobacterial response found in the field, we hypothesized that B. distachyon's response to H. seropedicae will be dynamic, will vary depending on the environment the plants are grown in (in our case with varying N availability), and in addition, will change through time. ...
N-fixation in cereals by root-associated bacteria is a promising solution to reducing chemical nitrogen fertilizer in agriculture. However, plant-bacterial responses are unpredictable across environments. We hypothesized that cereal responses to N-fixing bacteria are dynamic, depending on N supply and time. To quantify dynamics, the gnotobiotic, fabricated ecosystem (EcoFAB) was adapted to analyze N mass-balance, image shoot and root growth and measure gene expression of Brachypodium distachyon (Brachypodium) inoculated with N-fixing bacterium, Herbaspirillum seropedicae (Herbaspirillum). Phenotyping throughput of EcoFAB-N was 25-30 plants/h with open software and imaging systems.
Herbaspirillum inoculation of Brachypodium shifted root and shoot growth, nitrate versus ammonium uptake, and gene expression with time; directions and magnitude depending on N availability. Primary roots were longer and root hairs shorter regardless of N, with stronger changes at low N. At higher N, Herbaspirillum provided 11% total plant N from sources other than seed or nutrient solution. The time-resolved phenotypic and molecular data, points to distinct modes of action: At 5 mM the benefit appears through N fixation; while at 0.5 mM the mechanism appears to be plant physiological, with Herbaspirillum promoting uptake of N from the root medium.Future work could fine-tune plant and root-associated microorganisms to growth and nutrient dynamics.
