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15 pages, 4022 KiB

Open AccessArticle

Exploring the Organic Acid Secretion Pathway and Potassium Solubilization Ability of Pantoea vagans ZHS-1 for Enhanced Rice Growth

by Shiqi Tian, Yufeng Xu, Yanglin Zhong, Yaru Qiao, Dongchao Wang, Lei Wu, Xue Yang, Meiying Yang and Zhihai Wu

Plants 2024, 13(14), 1945; https://doi.org/10.3390/plants13141945 - 15 Jul 2024

Cited by 2 | Viewed by 1375

Abstract

Soil potassium deficiency is a common issue limiting agricultural productivity. Potassium-solubilizing bacteria (KSB) show significant potential in mitigating soil potassium deficiency, improving soil quality, and enhancing plant growth. However, different KSB strains exhibit diverse solubilization mechanisms, environmental adaptability, and growth-promoting abilities. In this [...] Read more.

Soil potassium deficiency is a common issue limiting agricultural productivity. Potassium-solubilizing bacteria (KSB) show significant potential in mitigating soil potassium deficiency, improving soil quality, and enhancing plant growth. However, different KSB strains exhibit diverse solubilization mechanisms, environmental adaptability, and growth-promoting abilities. In this study, we isolated a multifunctional KSB strain ZHS-1, which also has phosphate-solubilizing and IAA-producing capabilities. 16S rDNA sequencing identified it as Pantoea vagans. Scanning electron microscopy (SEM) showed that strain ZHS-1 severely corroded the smooth, compact surface of potassium feldspar into a rough and loose state. The potassium solubilization reached 20.3 mg/L under conditions where maltose was the carbon source, sodium nitrate was the nitrogen source, and the pH was 7. Organic acid metabolism profiling revealed that strain ZHS-1 primarily utilized the EMP-TCA cycle, supplemented by pathways involving pantothenic acid, glyoxylic acid, and dicarboxylic acids, to produce large amounts of organic acids and energy. This solubilization was achieved through direct solubilization mechanisms. The strain also secreted IAA through a tryptophan-dependent metabolic pathway. When strain ZHS-1 was inoculated into the rhizosphere of rice, it demonstrated significant growth-promoting effects. The rice plants exhibited improved growth and root development, with increased accumulation of potassium and phosphorus. The levels of available phosphorus and potassium in the rhizosphere soil also increased significantly. Additionally, we observed a decrease in the relative abundance of Actinobacteria and Proteobacteria in the rice rhizosphere soil, while the relative abundance of genera associated with acid production and potassium solubilization, such as Gemmatimonadota, Acidobacteria, and Chloroflexi, as well as Cyanobacteria, which are beneficial to plant growth, increased. These findings contribute to a deeper understanding of the potassium solubilization mechanisms of strain ZHS-1 and highlight its potential as a plant growth-promoting rhizobacteria. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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16 pages, 3234 KiB

Open AccessArticle

Expression of EPL1 from Trichoderma atroviride in Arabidopsis Confers Resistance to Bacterial and Fungal Pathogens

by Mónica Montserrat Rojas Moreno, Enrique González-Pérez, Aida Araceli Rodríguez-Hernandez, María Azucena Ortega-Amaro, Alicia Becerra-Flora, Mario Serrano and Juan Francisco Jiménez-Bremont

Plants 2023, 12(13), 2443; https://doi.org/10.3390/plants12132443 - 25 Jun 2023

Cited by 1 | Viewed by 2107

Abstract

During plant interaction with beneficial microorganisms, fungi secrete a battery of elicitors that trigger plant defenses against pathogenic microorganisms. Among the elicitor molecules secreted by Trichoderma are cerato-platanin proteins, such as EPL1, from Trichoderma atroviride. In this study, Arabidopsis thaliana plants that [...] Read more.

During plant interaction with beneficial microorganisms, fungi secrete a battery of elicitors that trigger plant defenses against pathogenic microorganisms. Among the elicitor molecules secreted by Trichoderma are cerato-platanin proteins, such as EPL1, from Trichoderma atroviride. In this study, Arabidopsis thaliana plants that express the TaEPL1 gene were challenged with phytopathogens to evaluate whether expression of EPL1 confers increased resistance to the bacterial pathogen Pseudomonas syringae and the necrotrophic fungus Botrytis cinerea. Infection assays showed that Arabidopsis EPL1-2, EPL1-3, EPL1-4 expressing lines were more resistant to both pathogens in comparison to WT plants. After Pseudomonas syringae infection, there were reduced disease symptoms (e.g., small chlorotic spots) and low bacterial titers in the three 35S::TaEPL1 expression lines. Similarly; 35S::TaEPL1 expression lines were more resistant to Botrytis cinerea infection, showing smaller lesion size in comparison to WT. Interestingly, an increase in ROS levels was detected in 35S::TaEPL1 expression lines when compared to WT. A higher expression of SA- and JA-response genes occurred in the 35S::TaEPL1 lines, which could explain the resistance of these EPL1 expression lines to both pathogens. We propose that EPL1 is an excellent elicitor, which can be used to generate crops with improved resistance to broad-spectrum diseases. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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14 pages, 3137 KiB

Open AccessArticle

Reduction in the Use of Some Herbicides Favors Nitrogen Fixation Efficiency in Phaseolus vulgaris and Medicago sativa

by Mario Paniagua-López, César Jiménez-Pelayo, Germán Orlando Gómez-Fernández, José Antonio Herrera-Cervera and Miguel López-Gómez

Plants 2023, 12(8), 1608; https://doi.org/10.3390/plants12081608 - 10 Apr 2023

Cited by 3 | Viewed by 2089

Abstract

In recent decades, the quality of agricultural soils has been seriously affected by the excessive application of pesticides, with herbicides being one of the most abundant. Continuous use of herbicides alters the soil microbial community and beneficial interactions between plants and bacteria such [...] Read more.

In recent decades, the quality of agricultural soils has been seriously affected by the excessive application of pesticides, with herbicides being one of the most abundant. Continuous use of herbicides alters the soil microbial community and beneficial interactions between plants and bacteria such as legume-rhizobia spp. symbiosis, causing a decrease in the biological nitrogen fixation, which is essential for soil fertility. Therefore, the aim of this work was to study the effect of two commonly used herbicides (pendimethalin and clethodim) on the legume-rhizobia spp. symbiosis to improve the effectiveness of this process. Phaseolus vulgaris plants grown in pots with a mixture of soil:perlite (3:1 v/v), showed a 44% inhibition of nitrogen fixation rate with pendimethalin. However, clethodim, specifically used against monocots, did not induce significant differences. Additionally, we analyzed the effect of herbicides on root exudate composition, detecting alterations that might be interfering with the symbiosis establishment. In order to assess the effect of the herbicides at the early nodulation steps, nodulation kinetics in Medicago sativa plants inoculated with Sinorhizobium meliloti were performed. Clethodim caused a 30% reduction in nodulation while pendimethalin totally inhibited nodulation, producing a reduction in bacterial growth and motility as well. In conclusion, pendimethalin and clethodim application reduced the capacity of Phaseolus vulgaris and Medicago sativa to fix nitrogen by inhibiting root growth and modifying root exudate composition as well as bacterial fitness. Thus, a reduction in the use of these herbicides in these crops should be addressed to favor a state of natural fertilization of the soil through greater efficiency of leguminous crops. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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10 pages, 2506 KiB

Open AccessCommunication

Studies on the Composition and Diversity of Seagrass Ruppia sinensis Rhizosphere Mmicroorganisms in the Yellow River Delta

by Shuai Shang, Liangyu Li, Hui Xiao, Jun Chen, Yu Zang, Jun Wang and Xuexi Tang

Plants 2023, 12(7), 1435; https://doi.org/10.3390/plants12071435 - 24 Mar 2023

Cited by 3 | Viewed by 1711

Abstract

Seagrass is a significant primary producer of coastal ecosystems; however, the continued degradation of seagrass beds is a serious problem that has attracted widespread attention from researchers. Rhizosphere microorganisms affect seagrass and participate in many life activities of seagrass. This study explored the [...] Read more.

Seagrass is a significant primary producer of coastal ecosystems; however, the continued degradation of seagrass beds is a serious problem that has attracted widespread attention from researchers. Rhizosphere microorganisms affect seagrass and participate in many life activities of seagrass. This study explored the relationship between the composition of microbes in the rhizosphere and the surrounding environment of Ruppia sinensis by using High-throughput sequencing methods. The dominant bacterial groups in the rhizosphere surface sediments of R. sinensis and the surrounding environment are Proteobacteria, Bacteroidota, and Firmicutes. Moreover, the dominant fungal groups are Ascomycota, Basidiomycota, and Chytridiomycota. Significant differences (p < 0.05) were identified in microbial communities among different groups (rhizosphere, bulk sediment, and surrounding seawater). Seventy-four ASVs (For bacteria) and 48 ASVs (For fungal) were shared among seagrass rhizosphere, surrounding sediment, and seawater. The rhizosphere was enriched in sulfate-reducing bacteria and nitrogen-fixing bacteria. In general, we obtained the rhizosphere microbial community of R. sinensis, which provided extensive evidence of the relative contribution of the seagrass rhizosphere and the surrounding environment. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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17 pages, 6752 KiB

Open AccessArticle

Identification and Characterization of Common Bean (Phaseolus vulgaris) Non-Nodulating Mutants Altered in Rhizobial Infection

by Rocío Reyero-Saavedra, Sara Isabel Fuentes, Alfonso Leija, Gladys Jiménez-Nopala, Pablo Peláez, Mario Ramírez, Lourdes Girard, Timothy G. Porch and Georgina Hernández

Plants 2023, 12(6), 1310; https://doi.org/10.3390/plants12061310 - 14 Mar 2023

Viewed by 2380

Abstract

The symbiotic N₂-fixation process in the legume–rhizobia interaction is relevant for sustainable agriculture. The characterization of symbiotic mutants, mainly in model legumes, has been instrumental for the discovery of symbiotic genes, but similar studies in crop legumes are scant. To isolate [...] Read more.

The symbiotic N₂-fixation process in the legume–rhizobia interaction is relevant for sustainable agriculture. The characterization of symbiotic mutants, mainly in model legumes, has been instrumental for the discovery of symbiotic genes, but similar studies in crop legumes are scant. To isolate and characterize common bean (Phaseolus vulgaris) symbiotic mutants, an ethyl methanesulphonate-induced mutant population from the BAT 93 genotype was analyzed. Our initial screening of Rhizobium etli CE3-inoculated mutant plants revealed different alterations in nodulation. We proceeded with the characterization of three non-nodulating (nnod), apparently monogenic/recessive mutants: nnod(1895), nnod(2353) and nnod(2114). Their reduced growth in a symbiotic condition was restored when the nitrate was added. A similar nnod phenotype was observed upon inoculation with other efficient rhizobia species. A microscopic analysis revealed a different impairment for each mutant in an early symbiotic step. nnod(1895) formed decreased root hair curling but had increased non-effective root hair deformation and no rhizobia infection. nnod(2353) produced normal root hair curling and rhizobia entrapment to form infection chambers, but the development of the latter was blocked. nnod(2114) formed infection threads that did not elongate and thus did not reach the root cortex level; it occasionally formed non-infected pseudo-nodules. The current research is aimed at mapping the responsible mutated gene for a better understanding of SNF in this critical food crop. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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23 pages, 2538 KiB

Open AccessEditor’s ChoiceArticle

Effects of Co-Inoculating Saccharomyces spp. with Bradyrhizobium japonicum on Atmospheric Nitrogen Fixation in Soybeans (Glycine max (L.))

by Obey Kudakwashe Zveushe, Victor Resco de Dios, Hengxing Zhang, Fang Zeng, Siqin Liu, Songrong Shen, Qianlin Kang, Yazhen Zhang, Miao Huang, Ahmed Sarfaraz, Matina Prajapati, Lei Zhou, Wei Zhang, Ying Han and Faqin Dong

Plants 2023, 12(3), 681; https://doi.org/10.3390/plants12030681 - 3 Feb 2023

Cited by 22 | Viewed by 4247

Abstract

Crop production encounters challenges due to the dearth of nitrogen (N) and phosphorus (P), while excessive chemical fertilizer use causes environmental hazards. The use of N-fixing microbes and P-solubilizing microbes (PSMs) can be a sustainable strategy to overcome these problems. Here, we conducted [...] Read more.

Crop production encounters challenges due to the dearth of nitrogen (N) and phosphorus (P), while excessive chemical fertilizer use causes environmental hazards. The use of N-fixing microbes and P-solubilizing microbes (PSMs) can be a sustainable strategy to overcome these problems. Here, we conducted a greenhouse pot experiment following a completely randomized blocked design to elucidate the influence of co-inoculating N-fixing bacteria (Bradyrhizobium japonicum) and PSMs (Saccharomyces cerevisiae and Saccharomyces exiguus) on atmospheric N₂-fixation, growth, and yield. The results indicate a significant influence of interaction on Indole-3-acetic acid production, P solubilization, seedling germination, and growth. It was also found that atmospheric N₂-fixation, nodule number per plant, nodule dry weight, straw, and root dry weight per plant at different growth stages were significantly increased under dual inoculation treatments relative to single inoculation or no inoculation treatment. Increased seed yield and N and P accumulation were also noticed under co-inoculation treatments. Soil available N was highest under sole bacterial inoculation and lowest under the control treatment, while soil available P was highest under co-inoculation treatments and lowest under the control treatment. We demonstrated that the co-inoculation of N-fixing bacteria and PSMs enhances P bioavailability and atmospheric N₂-fixation in soybeans leading to improved soil fertility, raising crop yields, and promoting sustainable agriculture. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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Review

Jump to: Research

29 pages, 1378 KiB

Open AccessEditor’s ChoiceReview

The Biosynthesis and Functions of Polyamines in the Interaction of Plant Growth-Promoting Rhizobacteria with Plants

by Michael F. Dunn and Víctor A. Becerra-Rivera

Plants 2023, 12(14), 2671; https://doi.org/10.3390/plants12142671 - 17 Jul 2023

Cited by 8 | Viewed by 2934

Abstract

Plant growth-promoting rhizobacteria (PGPR) are members of the plant rhizomicrobiome that enhance plant growth and stress resistance by increasing nutrient availability to the plant, producing phytohormones or other secondary metabolites, stimulating plant defense responses against abiotic stresses and pathogens, or fixing nitrogen. The [...] Read more.

Plant growth-promoting rhizobacteria (PGPR) are members of the plant rhizomicrobiome that enhance plant growth and stress resistance by increasing nutrient availability to the plant, producing phytohormones or other secondary metabolites, stimulating plant defense responses against abiotic stresses and pathogens, or fixing nitrogen. The use of PGPR to increase crop yield with minimal environmental impact is a sustainable and readily applicable replacement for a portion of chemical fertilizer and pesticides required for the growth of high-yielding varieties. Increased plant health and productivity have long been gained by applying PGPR as commercial inoculants to crops, although with uneven results. The establishment of plant–PGPR relationships requires the exchange of chemical signals and nutrients between the partners, and polyamines (PAs) are an important class of compounds that act as physiological effectors and signal molecules in plant–microbe interactions. In this review, we focus on the role of PAs in interactions between PGPR and plants. We describe the basic ecology of PGPR and the production and function of PAs in them and the plants with which they interact. We examine the metabolism and the roles of PAs in PGPR and plants individually and during their interaction with one another. Lastly, we describe some directions for future research. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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35 pages, 835 KiB

Open AccessEditor’s ChoiceReview

Contribution of Biofertilizers to Pulse Crops: From Single-Strain Inoculants to New Technologies Based on Microbiomes Strategies

by Gustavo Ribeiro Xavier, Ederson da Conceição Jesus, Anelise Dias, Marcia Reed Rodrigues Coelho, Yulimar Castro Molina and Norma Gouvêa Rumjanek

Plants 2023, 12(4), 954; https://doi.org/10.3390/plants12040954 - 20 Feb 2023

Cited by 8 | Viewed by 4911

Abstract

Pulses provide distinct health benefits due to their low fat content and high protein and fiber contents. Their grain production reaches approximately 93,210 × 10³ tons per year. Pulses benefit from the symbiosis with atmospheric N₂-fixing bacteria, which increases productivity [...] Read more.

Pulses provide distinct health benefits due to their low fat content and high protein and fiber contents. Their grain production reaches approximately 93,210 × 10³ tons per year. Pulses benefit from the symbiosis with atmospheric N₂-fixing bacteria, which increases productivity and reduces the need for N fertilizers, thus contributing to mitigation of environmental impact mitigation. Additionally, the root region harbors a rich microbial community with multiple traits related to plant growth promotion, such as nutrient increase and tolerance enhancement to abiotic or biotic stresses. We reviewed the eight most common pulses accounting for almost 90% of world production: common beans, chickpeas, peas, cowpeas, mung beans, lentils, broad beans, and pigeon peas. We focused on updated information considering both single-rhizobial inoculation and co-inoculation with plant growth-promoting rhizobacteria. We found approximately 80 microbial taxa with PGPR traits, mainly Bacillus sp., B. subtilis, Pseudomonas sp., P. fluorescens, and arbuscular mycorrhizal fungi, and that contributed to improve plant growth and yield under different conditions. In addition, new data on root, nodule, rhizosphere, and seed microbiomes point to strategies that can be used to design new generations of biofertilizers, highlighting the importance of microorganisms for productive pulse systems. Full article

(This article belongs to the Special Issue Interactions between Plants and Soil Microorganisms)

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