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Diazotrophic bacteria from maize exhibit multifaceted plant growth promotion traits in multiple hosts.

ABSTRACT: Sierra Mixe maize is a geographically remote landrace variety grown on nitrogen-deficient fields in Oaxaca, Mexico that meets its nutritional requirements without synthetic fertilizer by associating with free-living diazotrophs comprising the microbiota of its aerial root mucilage. We selected nearly 500 diazotrophic (N2-fixing) bacteria isolated from Sierra Mixe maize mucilage and sequenced their genomes. Comparative genomic analysis demonstrated that isolates represented diverse genera and composed three major diazotrophic groups based on nitrogen fixation gene content. In addition to nitrogen fixation, we examined deamination of 1-amino-1-cyclopropanecarboxylic acid, biosynthesis of indole-3-acetic acid, and phosphate solubilization as alternative mechanisms of direct plant growth promotion (PGP). Genome mining showed that isolates of all diazotrophic groups possessed marker genes for multiple mechanisms of direct plant growth promotion (PGP). Implementing in vitro assays corroborated isolate genotypes by measuring each isolate's potential to confer the targeted PGP traits and revealed phenotypic variation among isolates based on diazotrophic group assignment. Investigating the ability of mucilage diazotrophs to confer PGP by direct inoculation of clonally propagated potato plants in planta led to the identification of 16 bio-stimulant candidates. Conducting nitrogen-stress greenhouse experiments demonstrated that potato inoculation with a synthetic community of bio-stimulant candidates, as well as with its individual components, resulted in PGP phenotypes. We further demonstrated that one diazotrophic isolate conferred PGP to a conventional maize variety under nitrogen-stress in the greenhouse. These results indicate that, while many diazotrophic isolates from Sierra Mixe maize possessed genotypes and in vitro phenotypes for targeted PGP traits, a subset of these organisms promoted the growth of potato and conventional maize, potentially through the use of multiple promotion mechanisms.

SUBMITTER: Higdon SM

PROVIDER: S-EPMC7489573 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Diazotrophic bacteria from maize exhibit multifaceted plant growth promotion traits in multiple hosts.

Higdon Shawn M SM Pozzo Tania T Tibbett Emily J EJ Chiu Colleen C Jeannotte Richard R Weimer Bart C BC Bennett Alan B AB

PloS one 20200914 9

Sierra Mixe maize is a geographically remote landrace variety grown on nitrogen-deficient fields in Oaxaca, Mexico that meets its nutritional requirements without synthetic fertilizer by associating with free-living diazotrophs comprising the microbiota of its aerial root mucilage. We selected nearly 500 diazotrophic (N2-fixing) bacteria isolated from Sierra Mixe maize mucilage and sequenced their genomes. Comparative genomic analysis demonstrated that isolates represented diverse genera and com ...[more]

PMID: 32925972

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Project description:Several reports have described the involvement of miRNAs in abiotic stresses. However, their role in biotic stress or to beneficial microbes has not been fully explored. In order to understand on the epigenetic regulation in plant in response to nitrogen-fixing bacteria association, we analyzed the sRNA regulation in maize hybrids (Zea mays M-bM-^@M-^S UENF 506-8) inoculated with the beneficial diazotrophic bacteria (Herbaspirillum seropedicae). Deep sequencing analysis was carried out to identify the sRNAs regulated in maize during association with diazotrophic bacteria. For this analysis, maize plants were germinated in wet paper and put in hydroponic system with HoaglandM-bM-^@M-^Ys solution and then inoculated with H. seropedicae for seven days. Mock and inoculated plants were collected and total RNA from a pool of samples was extracted with Trizol reagent. The two sRNA libraries were sequenced by Illumina. The sequences were filtered to remove adaptors and contaminants rRNA and tRNAs, and sequences with 18-28 nt in length were selected. To identify the miRNAs present in these libraries, we used two strategies using the same website (http://srna-tools.cmp.uea.ac.uk): one to identify novel miRNAs using the maize genome (verson 2) and miRCat pipeline; and other to identify conserved miRNAs using the miRBase database (release 13.0, http://microrna.sanger.ac.uk) and miRProf pipeline. We identified 17 novel putative miRNAs candidates and mapped the precursor of these miRNAs in the maize genome. Furthermore, we identified 25 conserved miRNAs families and the differential expressions were analyzed with miRProf pipeline. The bioinformatics analysis of four up-regulated miRNAs (miR397, miR398, miR408 and miR528) in inoculated plant was validated using stemM-bM-^@M-^Sloop RT-PCR assay. Our findings contribute to increase the knowledge of the molecular relation between plants and endophytic bacteria. Screenning of sRNA transcriptome of maize plants inoculated with Herbaspirillum seropedicae after seven days

Project description:A diverse group of rhizobacteria persists in the rhizospheric soil, on the surface of roots, or in association with rice plants. These bacteria colonize plant root systems, enhance plant growth and crop yield. Indigenous rhizobacteria are known to promote soil health, grain production quality and serve as sustainable bioinoculant. The present study was aimed to isolate, identify and characterize indigenous plant growth promoting (PGP) diazotrophic bacteria associated with the rhizosphere of rice fields from different areas of Jammu and Kashmir, India. A total of 15 bacteria were isolated and evaluated for various PGP traits, antagonistic activity against phytopathogens, production of hydrolytic enzymes and biofilm formation under in-vitro conditions. The majority of the isolated bacteria were Gram-negative. Out of 15 bacterial isolates, nine isolates produced IAA (12.24 ± 2.86 to 250.3 ± 1.15 μg/ml), 6 isolates exhibited phosphate solubilization activity (36.69 ± 1.63 to 312.4 ± 1.15 μg/ml), 7 isolates exhibited rock phosphate solubilization while 5 isolates solubilized zinc (10-18 mm), 7 isolates showed siderophore production, 8 isolates exhibited HCN production, 6 isolates exhibited aminocyclopropane-1-carboxylate (ACC) deaminase activity, 13 isolates exhibited cellulase activity, nine isolates exhibited amylase and lipase activity and six isolates exhibited chitinase activity. In addition, 5 isolates showed amplification with the nifH gene and showed a significant amount of nitrogenase activity in a range of 0.127-4.39 μmol C2H4/mg protein/h. Five isolates viz., IHK-1, IHK-3, IHK-13, IHK-15 and IHK-25 exhibited most PGP attributes and successfully limited the mycelial growth of Rhizoctonia solani and Fusarium oxysporum in-vitro. All the five bacterial isolates were identified based on morphological, biochemical and 16S rDNA gene sequencing study, as Stenotrophomonas maltophilia, Enterobacter sp., Bacillus sp., Ochrobactrum haematophilum and Pseudomonas aeruginosa. Rice plants developed from seeds inoculated with these PGP strains individually had considerably higher germination percentage, seed vigor index and total dry biomass when compared to control. These findings strongly imply that the PGP diazotrophic bacteria identified in this work could be employed as plant growth stimulators in rice.

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Diazotrophic bacteria from maize exhibit multifaceted plant growth promotion traits in multiple hosts.

Publications

Diazotrophic bacteria from maize exhibit multifaceted plant growth promotion traits in multiple hosts.

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