The Bacillus amyloliquefaciens-SN13 and model crop rice (Oryza sativa) were chosen to understand the complex regulatory networks that govern plant-PGPR interaction under salt stress. During stress, ...inoculation with SN13 significantly increased biomass, relative water content, proline and total soluble sugar in rice while decreased lipid peroxidation and electrolyte leakage. Extensive alterations in gene expression were also observed in rice root transcriptome under stress in the presence of SN13. Rhizobacteria induced changes in expression of a considerable number of photosynthesis, hormone, and stress-responsive genes, in addition to cell-wall and lipid metabolism-related genes under salt stress as compared to salt stress or SN13 inoculation alone, indicating its potential role in reducing the harmful effects of salinity. To validate RNA-seq data, qRT-PCR was performed for selected differentially expressed genes representing various functional categories including metabolism, regulation, stress-response, and transporters. Results indicate qualitative and quantitative differences between roots responses to SN13 under stressed and unstressed conditions. Functional expressions of OsNAM and OsGRAM in yeast showed enhanced tolerance to various abiotic stresses, indicating crucial SN13-rice interaction in imparting beneficial effects under stress. This is first detailed report on understanding molecular mechanism underlying beneficial plant-microbe interaction in any economically important model crop plant under abiotic stress.
Community level physiological profiling and pyrosequencing-based analysis of the V1-V2 16S rRNA gene region were used to characterize and compare microbial community structure, diversity, and ...bacterial phylogeny from soils of chemically cultivated land (CCL), organically cultivated land (OCL), and fallow grass land (FGL) for 16 years and were under three different land use types. The entire dataset comprised of 16,608 good-quality sequences (CCL, 6,379; OCL, 4,835; FGL, 5,394); among them 12,606 sequences could be classified in 15 known phylum. The most abundant phylum were Proteobacteria (29.8%), Acidobacteria (22.6%), Actinobacteria (11.1%), and Bacteroidetes (4.7%), while 24.3% of the sequences were from bacterial domain but could not be further classified to any known phylum. Proteobacteria, Bacteroidetes, and Gemmatimonadetes were found to be significantly abundant in OCL soil. On the contrary, Actinobacteria ana Acidobacteria were significantly abundant in CCL and FGL, respectively. Our findings supported the view that organic compost amendment (OCL) activates diverse group of microorganisms as compared with conventionally used synthetic chemical fertilizers. Functional diversity and evenness based on carbon source utilization pattern was significantly higher in OCL as compared to CCL and FGL, suggesting an improvement in soil quality. This abundance of microbes possibly leads to the enhanced level of soil organic carbon, soil organic nitrogen, and microbial biomass in OCL and FGL soils as collated with CCL. This work increases our current understanding on the effect of long-term organic and chemical amendment applications on abundance, diversity, and composition of bacterial community inhabiting the soil for the prospects of agricultural yield and quantity of soil.
Growth and productivity of rice and soil inhabiting microbial population is negatively affected by soil salinity. However, some salt resistant, rhizosphere competent bacteria improve plant health in ...saline stress. Present study evaluated the effect of salt tolerant Bacillus amyloliquefaciens NBRISN13 (SN13) inoculation on rice plants in hydroponic and soil conditions exposed to salinity. SN13 increased plant growth and salt tolerance (NaCl 200 mM) and expression of at least 14 genes under hydroponic and soil conditions in rice. Among these 14 genes 4 (NADP-Me2, EREBP, SOSI, BADH and SERK1) were up-regulated and 2 (GIG and SAPK4) repressed under salt stress in hydroponic condition. In greenhouse experiment, salt stress resulted in accumulation of MAPK5 and down-regulation of the remaining 13 transcripts was observed. SN13 treatment, with or without salt gave similar expression for all tested genes as compared to control. Salt stress caused changes in the microbial diversity of the rice rhizosphere and stimulated population of betaine-, sucrose-, trehalose-, and glutamine-utilizing bacteria in salt-treated rice rhizosphere (SN13 + salt). The observations imply that SN13 confers salt tolerance in rice by modulating differential transcription in a set of at least 14 genes. Stimulation of osmoprotectant utilizing microbial population as a mechanism of inducing salt tolerance in rice is reported for the first time in this study to the best of our knowledge.
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► PGPR Bacillus amyloliquefaciens NBRISN13 (SN13) promotes growth of rice plants under salt stress. ► SN13 modulates gene expression in rice under salt-stressed condition. ► Salt stress leads to changes in microbial diversity of the rice rhizosphere which can be neutralized by SN13. ► SN13 alters rice rhizosphere by increasing the osmoprotectant utilizing microflora in the soil under normal and salt stress.
Biosynthesis of nanoparticles has gained great attention in making the process cost-effective and eco-friendly, but there are limited reports which describe the interdependency of physical parameters ...for tailoring the dimension and geometry of nanoparticles during biological synthesis. In the present study, gold nanoparticles (GNPs) of various shapes and sizes were obtained by modulating different physical parameters using Trichoderma viride filtrate. The particles were characterized on the basis of visual observation, dynamic light scattering, UV-visible spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy, and X ray diffraction. While the size varied from 2-500 nm, the shapes obtained were nanospheres, nanotriangles, nanopentagons, nanohexagons, and nanosheets. Changing the parameters such as pH, temperature, time, substrate, and culture filtrate concentration influenced the size and geometry of nanoparticles. Catalytic activity of the biosynthesized GNP was evaluated by UV-visible spectroscopy and confirmed by gas chromatography-mass spectrometric analysis for the conversion of 4-nitrophenol into 4-aminophenol which was strongly influenced by their structure and dimension. Common practices for biodegradation are traditional, expensive, require large amount of raw material, and time taking. Controlling shapes and sizes of nanoparticles could revolutionize the process of biodegradation that can remove all the hurdles in current scenario.
Previous studies with Paenibacillus lentimorbus B-30488" (hereafter referred as B-30488), a plant growth promoting rhizobacteria (PGPR) isolated from cow's milk, revealed its capabilities to improve ...plant quality under normal and stress conditions. Present study investigates its potential as a biocontrol agent against an economically important virus, Cucumber mosaic virus (CMV), in Nicotiana tabacum cv. White Burley plants and delineates the physical, biophysical, biochemical and molecular perturbations due to the trilateral interactions of PGPR-host-CMV. Soil inoculation of B-30488 enhanced the plant vigor while significantly decreased the virulence and virus RNA accumulation by ~12 fold (91%) in systemic leaves of CMV infected tobacco plants as compared to the control ones. Histology of these leaves revealed the improved tissue's health and least aging signs in B-30488 inoculated tobacco plants, with or without CMV infection, and showed lesser intercellular spaces between collenchyma cells, reduced amount of xyloglucans and pectins in connecting primary cells, and higher polyphenol accumulation in hypodermis layer extending to collenchyma cells. B-30488 inoculation has favorably maneuvered the essential biophysical (ion leakage and photosynthetic efficiency) and biochemical (sugar, proline, chlorophyll, malondialdehyde, acid phosphatase and alkaline phosphatase) attributes of tobacco plants to positively regulate and release the virus stress. Moreover, activities of defense related enzymes (ascorbate peroxidase, guaiacol peroxidase, superoxide dismutase and catalase) induced due to CMV-infection were ameliorated with inoculation of B-30488, suggesting systemic induced resistance mediated protection against CMV in tobacco. The quantitative RT-PCR analyses of the genes related to normal plant development, stress and pathogenesis also corroborate well with the biochemical data and revealed the regulation (either up or down) of these genes in favor of plant to combat the CMV mediated stress. These improvements led tobacco plant to produce more flowers and seeds with no negative impact on plant health. The present study may advocate the applicability of B-30488 for crop yield improvement in virus infested areas.
Abstract
The major problem encountered during genetic manipulation of bacteria is the inability to get transformed because of their natural non-competency. In this study, to overcome this problem, a ...cost-effective method was developed by combining the properties of gold nanoparticles (GNPs) and the Yoshida effect. Various parameters, including GNP:plasmid ratio, pH and time, were optimized for stability of the GNP–plasmid conjugate. With non-competent Gram-negative cells, the efficiency ranged between 0.1 and 0.45 × 104 transformants μg−1, while the range was (0.02–0.2) × 104 transformants μg−1 with Gram-positive bacteria. GNPs can serve efficiently as a vehicle for better transformation in bacteria.
Biogenic gold nanoparticles mediate transformation in both Gram-negative and Gram-positive bacterial cells.
Drought is the major abiotic factors that limit crop productivity worldwide. To withstand stress conditions, plants alter numerous mechanisms for adaption and tolerance. Therefore, in the present ...study, 106 rice varieties were screened for drought tolerance phenotype via exposing different concentrations of polyethylene glycol 6000 (PEG) in the hydroponic nutrient medium at the time interval of 1, 3, and 7 days to evaluate the changes in their root system architecture. Further, based on root phenotype obtained after PEG-induced drought, two contrasting varieties drought-tolerant Heena and -sensitive Kiran were selected to study transcriptional and physiological alterations at the same stress durations. Physiological parameters (photosynthesis rate, stomatal conductance, transpiration), and non-enzymatic antioxidants (carotenoids, anthocyanins, total phenol content) production indicated better performance of Heena than Kiran. Comparatively higher accumulation of carotenoid and anthocyanin content and the increased photosynthetic rate was also observed in Heena. Root morphology (length, numbers of root hairs, seminal roots and adventitious roots) and anatomical data (lignin deposition, xylem area) enable tolerant variety Heena to better maintain membrane integrity and relative water content, which also contribute to comparatively higher biomass accumulation in Heena under drought. In transcriptome profiling, significant drought stress-associated differentially expressed genes (DEGs) were identified in both the varieties. A total of 1033 and 936 uniquely upregulated DEGs were found in Heena and Kiran respectively. The significant modulation of DEGs that were mainly associated with phytohormone signaling, stress-responsive genes (LEA, DREB), transcription factors (TFs) (AP2/ERF, MYB, WRKY, bHLH), and genes involved in photosynthesis and antioxidative mechanisms indicate better adaptive nature of Heena in stress tolerance. Additionally, the QTL-mapping analysis showed a very high number of DEGs associated with drought stress at AQHP069 QTL in Heena in comparison to Kiran which further distinguishes the drought-responsive traits at the chromosomal level in both the contrasting varieties. Overall, results support the higher capability of Heena over Kiran variety to induce numerous genes along with the development of better root architecture to endure drought stress.
•106 rice varieties were screened to evaluate drought stress-responsive traits.•Two contrasting cultivars Heena and Kiran were selected for comparative analysis.•Transcriptome reveals extensive alteration in metabolic and regulatory pathways.•Overall comparative differences reveal drought tolerance mechanism in rice.
Plant-growth-promoting rhizobacteria (PGPR) improve plant growth by altering the root architecture, although the mechanisms underlying this alteration have yet to be unravelled. Through microarray ...analysis of PGPR-treated rice roots, a large number of differentially regulated genes were identified. Ectopic expression of one of these genes, OsASR6 (ABA STRESS RIPENING6), had a remarkable effect on plant growth in Arabidopsis. Transgenic lines over-expressing OsASR6 had larger leaves, taller inflorescence bolts and greater numbers of siliques and seeds. The most prominent effect was observed in root growth, with the root biomass increasing four-fold compared with the shoot biomass increase of 1.7-fold. Transgenic OsASR6 over-expressing plants showed higher conductance, transpiration and photosynthesis rates, leading to an ˜30% higher seed yield compared with the control. Interestingly, OsASR6 expression led to alterations in the xylem structure, an increase in the xylem vessel size and altered lignification, which correlated with higher conductance. OsASR6 is activated by auxin and, in turn, increases auxin responses and root auxin sensitivity, as observed by the increased expression of auxin-responsive genes, such as SAUR32 and PINOID, and the key auxin transcription factor, ARF5. Collectively, these phenomena led to an increased root density. The effects of OsASR6 expression largely mimic the beneficial effects of PGPRs in rice, indicating that OsASR6 activation may be a key factor governing PGPR-mediated changes in rice. OsASR6 is a potential candidate for the manipulation of rice for improved productivity.
A simple and facile way of using biogenic silver nanoparticles (BSNP) (10-20 nm) was developed for wound healing acceleration and suppression of wound infections. The BSNP were formulated in an ...ointment base, and the study to accelerate the wound healing process was conducted in a rat. The pH of the BSNP ointment, pH 6.8 ± 0.5, lies in normal pH range of the human skin, with good spreadability and diffusibility. The wound closure rate, as a percentage, was highest at day 3 for a BSNP ointment-treated wound at 22.77 ± 1.60%, while in an untreated control the rate was 10.99 ± 1.74%, for Betadine 14.73 ± 2.36% and for Soframycin 18.55 ± 1.37%, compared with day 0. A similar pattern of wound closure rate was found at days 7 and 11. The antibacterial activity of BSNP was evaluated against wound-infection-causing bacteria Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli by the agar diffusion method. The total bacterial counts in the wound area were enumerated by the colony forming unit method. The lowest number of bacterial counts was found in the BSNP-treated wound compared with the other groups. BSNP treatment at 7.5% concentration enhanced migration of fibroblasts in a scratch assay. These findings reveal BSNP as an efficient contrivance for wound healing acceleration and as an eco-friendly alternative therapeutic antimicrobial agent.
► Present study describes novel medium (PAM) for screening phosphate-accumulating organisms. ► PAM serves as a synergistic microbiological growth medium for preferential screening of PAOs. ► ...Efficiency of screening PAOs enhanced by PAM-TBO assay in 96 well microplate platform. ► Our simple high throughput protocol significantly reduced time for screening PAOs. ► It is envisaged that use of this protocol will be salutary for the quick screening of PAOs.
A novel PA Medium (PAM) for efficient screening of phosphate-accumulating organisms (PAOs) was developed taking Serratia marcescens NBRI1213 as model organism. The defined National Botanical Research Institute’s growth medium (NBRI) supplemented with 0.1% maltose, designed for quantitative estimation of phosphate accumulation was designated as PAM. Our work suggested usage of PAM for efficient qualitative screening and as a microbiological medium for preferential selection of PAOs on Petri-plates. For qualitative screening of PAOs, Toluidine blue-O dye (TBO) was supplemented in PAM, designated as PAM-TBO. Qualitative analysis of phosphate accumulated by various groups correlated well with grouping based upon quantitative analysis of PAOs, effect of carbon, nitrogen, salts, and phosphate accumulation-defective transposon mutants. For significantly increasing sample throughput, efficiency of screening PAOs was further enhanced by adaptation of PAM-TBO assay to microtiter plate based method. It is envisaged that usage of this medium will be salutary for quick screening of PAOs from environment.
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