Unveiling the putative functional genes present in root-associated endophytic microbiome from maize plant using the shotgun approach

Drought Stress Amelioration Attributes of Plant-Associated Microbiome on Agricultural Plants

The future global food security depends on the availability of water for agriculture. Yet, the ongoing rise in nonagricultural uses for water, such as urban and industrial uses, and growing environmental quality concerns have increased pressure of irrigation water demand and posed danger to food security. Nevertheless, its severity and duration are predicted to rise shortly. Drought pressure causes stunted growth, severe damage to photosynthesis activity, loss in crop yield, reduced seed germination, and reduced nutrient intake by plants. To overcome the effects of a devastating drought on plants, it is essential to think about the causes, mechanisms of action, and long-term agronomy management and genetics. As a result, there is an urgent need for long-term medication to deal with the harmful effects of drought pressure. The review focuses on the adverse impact of drought on the plant, physiological, and biochemical aspects, and management measures to control the severity of drought conditions. This article reviews the role of genome editing (GE) technologies such as CRISPR 9 (CRISPR-Cas9) related spaces and short palindromic relapse between proteins in reducing the effects of phytohormones, osmolytes, external compounds, proteins, microbes (plant growth-promoting microorganism [PGPM]), approach omics, and drought on plants that support plant growth. This research is to examine the potential of using the microbiome associated with plants for drought resistance and sustainable agriculture. Researchers also advocate using a mix of biotechnology, agronomic, and advanced GE technologies to create drought-tolerant plant varieties.

Metagenomic profiling of tomato rhizosphere delineates the diverse nature of uncultured microbes as influenced by Bacillus velezensis VB7 and Trichoderma koningiopsis TK towards the suppression of root-knot nematode under field conditions

The plant-parasitic Root Knot Nematodes (Meloidogyne spp.,) play a pivotal role to devastate vegetable crops across the globe. Considering the significance of plant-microbe interaction in the suppression of Root Knot Nematode, we investigated the diversity of microbiome associated with bioagents-treated and nematode-infected rhizosphere soil samples through metagenomics approach. The wide variety of organisms spread across different ecosystems showed the highest average abundance within each taxonomic level. In the rhizosphere, Proteobacteria, Firmicutes, and Actinobacteria were the dominant bacterial taxa, while Ascomycota, Basidiomycota, and Mucoromycota were prevalent among the fungal taxa. Regardless of the specific treatments, bacterial genera like Bacillus, Sphingomonas, and Pseudomonas were consistently found in high abundance. Shannon diversity index vividly ensured that, bacterial communities were maximum in B. velezensis VB7-treated soil (1.4-2.4), followed by Root Knot Nematode-associated soils (1.3-2.2), whereas richness was higher with Trichoderma konigiopsis TK drenched soils (1.3-2.0). The predominant occurrence of fungal genera such as Aspergillus Epicoccum, Choanephora, Alternaria and Thanatephorus habituate rhizosphere soils. Shannon index expressed the abundant richness of fungal species in treated samples (1.04-0.90). Further, refraction and species diversity curve also depicted a significant increase with maximum diversity of fungal species in B. velezensis VB7-treated soil than T. koningiopsis and nematode-infested soil. In field trial, bioagents-treated tomato plant (60% reduction of Meloidogyne incognita infection) had reduced gall index along with enhanced plant growth and increased fruit yield in comparison with the untreated plant. Hence, B. velezensis VB7 and T. koingiopsis can be well explored as an antinemic bioagents against RKN.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03851-1.

Endosphere microbial communities and plant nutrient acquisition toward sustainable agriculture

Endophytic microbial communities have essential information for scientists based on their biological contribution to agricultural practices. In the external plant environment, biotic and abiotic factors affect microbial populations before getting into plant tissues. Endophytes are involved in mutualistic and antagonistic activities with the host plant. Microbial communities inhabiting the internal tissues of plant roots depend on their ability to live and contend with other plant microflora. The advantageous ones contribute to soil health and plant growth either directly or indirectly. The microbial communities move via soil-root environment into the endosphere of plants promoting plant growth features like antibiosis, induced systemic resistance, phytohormone synthesis, and bioremediation. Therefore, the existence of these microorganisms contributes to plant genomes, nutrient availability in the soil, the presence of pathogens, and abiotic factors. This review aims at how endophytic microorganisms have displayed great interest in contributing to abundant crop production and phytopathogen inhibition.

Divergent endophytic viromes and phage genome repertoires among banana (Musa) species

Introduction

Viruses generally cause disease, but some viruses may be beneficial as resident regulators of their hosts or host microbiomes. Plant-associated viruses can help plants survive by increasing stress tolerance or regulating endophytic communities. The goal of this study was to characterize endophytic virus communities in banana and plantain (Musa spp.) genotypes, including cultivated and wild species, to assess virome repertoires and detect novel viruses.

Methods

DNA viral communities were characterized by shotgun sequencing of an enriched endosphere extract from leaves and roots or corm of 7 distinct Musa genotypes (M. balbisiana, Thai Black, M. textilis, M. sikkimensis, Dwarf Cavendish, Williams Hybrid, and FHIA-25 Hybrid).

Results

Results showed abundant virus-like contigs up to 108,191 bp long with higher relative abundance in leaves than roots. Analyses predicted 733 phage species in 51 families, with little overlap in phage communities among plants. Phage diversity was higher in roots and in diploid wild hosts. Ackermanniviridae and Rhizobium phage were generally the most abundant taxa. A Rhizobium RR1-like phage related to a phage of an endophytic tumor-causing rhizobium was found, bearing a holin gene and a partial Shiga-like toxin gene, raising interest in its potential to regulate endophytic Rhizobiaceae. Klebsiella phages were of interest for possible protection against Fusarium wilt, and other phages were predicted with potential to regulate Erwinia, Pectobacterium, and Ralstonia-associated diseases. Although abundant phage-containing contigs were functionally annotated, revealing 1,038 predicted viral protein domains, gene repertoires showed high divergence from database sequences, suggesting novel phages in these banana cultivars. Plant DNA viruses included 56 species of Badnavirus and 26 additional non-Musa plant viruses with distributions that suggested a mixture of resident and transient plant DNA viruses in these samples.

Discussion

Together, the disparate viral communities in these plants from a shared environment suggest hosts drive the composition of these virus communities. This study forms a first step in understanding the endophytic virome in this globally important food crop, which is currently threatened by fungal, bacterial, and viral diseases.

Unraveling the functional genes present in rhizosphere microbiomes of Solanum lycopersicum

The microbiomes living in the rhizosphere soil of the tomato plant contribute immensely to the state of health of the tomato plant alongside improving sustainable agriculture. With the aid of shotgun metagenomics sequencing, we characterized the putative functional genes (plant-growth-promoting and disease-resistant genes) produced by the microbial communities dwelling in the rhizosphere soil of healthy and powdery mildew-diseased tomato plants. The results identified twenty-one (21) plant growth promotion (PGP) genes in the microbiomes inhabiting the healthy rhizosphere (HR) which are more predomiant as compared to diseased rhizosphere (DR) that has nine (9) genes and four (4) genes in bulk soil (BR). Likewise, we identified some disease-resistant genes which include nucleotide binding genes and antimicrobial genes. Our study revealed fifteen (15) genes in HR which made it greater in comparison to DR that has three (3) genes and three (3) genes in bulk soil. Further studies should be conducted by isolating these microorganisms and introduce them to field experiments for cultivation of tomatoes.

Metapangenomics of wild and cultivated banana microbiome reveals a plethora of host-associated protective functions

BACKGROUND

Microbiomes are critical to plants, promoting growth, elevating stress tolerance, and expanding the plant's metabolic repertoire with novel defense pathways. However, generally microbiomes within plant tissues, which intimately interact with their hosts, remain poorly characterized. These endospheres have become a focus in banana (Musa spp.)-an important plant for study of microbiome-based disease protection. Banana is important to global food security, while also being critically threatened by pandemic diseases. Domestication and clonal propagation are thought to have depleted protective microbiomes, whereas wild relatives may hold promise for new microbiome-based biological controls. The goal was to compare metapangenomes enriched from 7 Musa genotypes, including wild and cultivated varieties grown in sympatry, to assess the host associations with root and leaf endosphere functional profiles.

RESULTS

Density gradients successfully generated culture-free microbial enrichment, dominated by bacteria, with all together 24,325 species or strains distinguished, and 1.7 million metagenomic scaffolds harboring 559,108 predicted gene clusters. About 20% of sequence reads did not match any taxon databases and ~ 62% of gene clusters could not be annotated to function. Most taxa and gene clusters were unshared between Musa genotypes. Root and corm tissues had significantly richer endosphere communities that were significantly different from leaf communities. Agrobacterium and Rhizobium were the most abundant in all samples while Chitinophagia and Actinomycetia were more abundant in roots and Flavobacteria in leaves. At the bacterial strain level, there were > 2000 taxa unique to each of M. acuminata (AAA genotype) and M. balbisiana (B-genotype), with the latter 'wild' relatives having richer taxa and functions. Gene ontology functional enrichment showed core beneficial functions aligned with those of other plants but also many specialized prospective beneficial functions not reported previously. Some gene clusters with plant-protective functions showed signatures of phylosymbiosis, suggesting long-standing associations or heritable microbiomes in Musa.

CONCLUSIONS

Metapangenomics revealed key taxa and protective functions that appeared to be driven by genotype, perhaps contributing to host resistance differences. The recovery of rich novel taxa and gene clusters provides a baseline dataset for future experiments in planta or in vivo bacterization or engineering of wild host endophytes.

Understanding the plant-microbe interactions in environments exposed to abiotic stresses: An overview

Abiotic stress poses a severe danger to agriculture since it negatively impacts cellular homeostasis and eventually stunts plant growth and development. Abiotic stressors like drought and excessive heat are expected to occur more frequently in the future due to climate change, which would reduce the yields of important crops like maize, wheat, and rice which may jeopardize the food security of human populations. The plant microbiomes are a varied and taxonomically organized microbial community that is connected to plants. By supplying nutrients and water to plants, and regulating their physiology and metabolism, plant microbiota frequently helps plants develop and tolerate abiotic stresses, which can boost crop yield under abiotic stresses. In this present study, with emphasis on temperature, salt, and drought stress, we describe current findings on how abiotic stresses impact the plants, microbiomes, microbe-microbe interactions, and plant-microbe interactions as the way microorganisms affect the metabolism and physiology of the plant. We also explore crucial measures that must be taken in applying plant microbiomes in agriculture practices faced with abiotic stresses.

Bacterial bioinoculants adapted for sustainable plant health and soil fertility enhancement in Namibia

The increase in dryland agriculture elicits the need to develop sustainable practices that improve crop yield and protect soil fertility. The use of biofertilisers adapted to nutrient deficient soils and arid climates would help achieve this. In this review, the use of plant growth-promoting bacteria is explored as a possible solution to the current state of dryland agriculture and climate change threats to agriculture. Plant microbe interactions form the basis of this review as evidence has shown that these interactions often exist to improve the health of plants. This is achieved by the production of important biochemicals and enzymes like indole acetic acid and amino cyclopropane-1-carboxylate deaminase while also actively protecting plants from pathogens including fungal pathogens. Research, therefore, has shown that these plant-growth promoting bacteria may be exploited and developed into biofertilisers. These biofertilisers are both economically and environmentally sustainable while improving soil quality and crop yield. The literature presented in this review is in context of the Namibian climate and soil profiles.

Contrasting genome patterns of two pseudomonas strains isolated from the date palm rhizosphere to assess survival in a hot arid environment

The plant growth-promoting rhizobacteria (PGPRs) improve plant growth and fitness by multiple direct (nitrogen fixation and phosphate solubilization) and indirect (inducing systematic resistance against phytopathogens, soil nutrient stabilization, and maintenance) mechanisms. Nevertheless, the mechanisms by which PGPRs promote plant growth in hot and arid environments remain poorly recorded. In this study, a comparative genome analysis of two phosphate solubilizing bacteria, Pseudomonas atacamensis SM1 and Pseudomonas toyotomiensis SM2, isolated from the rhizosphere of date palm was performed. The abundance of genes conferring stress tolerance (chaperones, heat shock genes, and chemotaxis) and supporting plant growth (plant growth hormone, root colonization, nitrogen fixation, and phosphate solubilization) were compared among the two isolates. This study further evaluated their functions, metabolic pathways, and evolutionary relationship. Results show that both bacterial strains have gene clusters required for plant growth promotion (phosphate solubilization and root colonization), but it is more abundant in P. atacamensis SM1 than in P. toyotomiensis SM2. Genes involved in stress tolerance (mcp, rbs, wsp, and mot), heat shock, and chaperones (hslJ and hslR) were also more common in P. atacamensis SM1. These findings suggest that P. atacamensis SM1could have better adaptability to the hot and arid environment owing to a higher abundance of chaperone genes and heat shock proteins. It may promote plant growth owing to a higher load of root colonization and phosphate solubilization genes and warrants further in vitro study.

Strategies to Enhance the Use of Endophytes as Bioinoculants in Agriculture

The findings on the strategies employed by endophytic microbes have provided salient information to the researchers on the need to maximally explore them as bio-input in agricultural biotechnology. Biotic and abiotic factors are known to influence microbial recruitments from external plant environments into plant tissues. Endophytic microbes exhibit mutualism or antagonism association with host plants. The beneficial types contribute to plant growth and soil health, directly or indirectly. Strategies to enhance the use of endophytic microbes are desirable in modern agriculture, such that these microbes can be applied individually or combined as bioinoculants with bioprospecting in crop breeding systems. Scant information is available on the strategies for shaping the endophytic microbiome; hence, the need to unravel microbial strategies for yield enhancement and pathogen suppressiveness have become imperative. Therefore, this review focuses on the endophytic microbiome, mechanisms, factors influencing endophyte recruitment, and strategies for possible exploration as bioinoculants.

The endophytome (plant-associated microbiome): methodological approaches, biological aspects, and biotech applications

Similar to other organisms, plants establish interactions with a variety of microorganisms in their natural environment. The plant microbiome occupies the host plant's tissues, either internally or on its surfaces, showing interactions that can assist in its growth, development, and adaptation to face environmental stresses. The advance of metagenomics and metatranscriptomics approaches has strongly driven the study and recognition of plant microbiome impacts. Research in this regard provides comprehensive information about the taxonomic and functional aspects of microbial plant communities, contributing to a better understanding of their dynamics. Evidence of the plant microbiome's functional potential has boosted its exploitation to develop more ecological and sustainable agricultural practices that impact human health. Although microbial inoculants' development and use are promising to revolutionize crop production, interdisciplinary studies are needed to identify new candidates and promote effective practical applications. On the other hand, there are challenges in understanding and analyzing complex data generated within a plant microbiome project's scope. This review presents aspects about the complex structuring and assembly of the microbiome in the host plant's tissues, metagenomics, and metatranscriptomics approaches for its understanding, covering descriptions of recent studies concerning metagenomics to characterize the microbiome of non-model plants under different aspects. Studies involving bio-inoculants, isolated from plant microbial communities, capable of assisting in crops' productivity, are also reviewed.

Genomic assessment of Stenotrophomonas indicatrix for improved sunflower plant

Diverse agriculturally important microbes have been studied with known potential in plant growth promotion. Providing several opportunities, Stenotrophomonas species are characterized as promising plant enhancers, inducers, and protectors against environmental stressors. The S. indicatrix BOVIS40 isolated from the sunflower root endosphere possessed unique features, as genome insights into the Stenotrophomonas species isolated from oilseed crops in Southern Africa have not been reported. Plant growth-promotion screening and genome analysis of S. indicatrix BOVIS40 were presented in this study. The genomic information reveals various genes underlining plant growth promotion and resistance to environmental stressors. The genome of S. indicatrix BOVIS40 harbors genes involved in the degradation and biotransformation of organic molecules. Also, other genes involved in biofilm production, chemotaxis, and flagellation that facilitate bacterial colonization in the root endosphere and phytohormone genes that modulate root development and stress response in plants were detected in strain BOVIS40. IAA activity of the bacterial strain may be a factor responsible for root formation. A measurable approach to the S. indicatrix BOVIS40 lifestyle can strategically provide several opportunities in their use as bioinoculants in developing environmentally friendly agriculture sustainably. The findings presented here provide insights into the genomic functions of S. indicatrix BOVIS40, which has set a foundation for future comparative studies for a better understanding of the synergism among microbes inhabiting plant endosphere. Hence, highlighting the potential of S. indicatrix BOVIS40 upon inoculation under greenhouse experiment, thus suggesting its application in enhancing plant and soil health sustainably.