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.
Introduction: Drought stress is one of the most important abiotic stresses that negatively
influence crop performance and productivity. Plants acclimatize to drought stress conditions through
altered ...molecular, biochemical and physiological responses. Gene and/or protein expression and regulation
are thought to be modulated upon stress perception and signal transduction for providing requisite
endurance to plants.
Plant growth regulators or phytohormones are important molecules required for various biological
processes in plants and are also central to stress signalling pathways. Among various phytohormones,
Abscisic Acid (ABA) and Ethylene (ET) are considered to be the most vital growth regulators implicated
in drought stress signalling and tolerance. Besides the above two known classical phytohormones,
Salicylic Acid (SA) and Jasmonic Acid (JA) have also been found to potentially enhance abiotic
stress tolerance particularly that of drought, salinity, and heat stress tolerance in plants. Apart
from these several other growth regulators such as Cytokinins (CKs), Auxin (AUX), Gibberellic Acid
(GA), Brassinosteroids (BRs) and Strigolactones (SLs) have also been reported to actively participate
in abiotic stress responses and tolerance in plants. The abiotic stress signalling in plants regulated by
these hormones further depends upon the nature, intensity, and duration of exposure to various environmental
stresses. It has been reported that all these phytohormones are also involved in extensive
crosstalk and signal transduction among themselves and/or with other factors.
Conclusion: This review thus summarizes the molecular mechanism of drought signalling and its crosstalk
with various phytohormone signalling pathways implicated in abiotic stress response and tolerance.
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.
Chickpea (
Cicer arietinum
L.) is a pulse crop valued for its high protein content, grown in semi-arid tropics and Mediterranean regions. Its yield remains affected by biotic and abiotic stresses ...with drought alone being responsible for up to 50% annual loss of yield. Transcriptome analysis of a sensitive and a tolerant cultivar of chickpea has been done earlier to unravel the molecular basis for drought and salinity stress responses. In the present study, we performed transcriptome analysis of two drought-tolerant genotypes, BG-362 and P-256, under polyethylene glycol-simulated drought stress to decipher the genes and pathways that are commonly regulated in these genotypes. RNA-Seq using Illumina platform generated 152 million high-quality reads. Reference-guided assembly of genome yielded a total of 37,943 transcripts representing 22,701 genes. Among the 1624 genes that were observed to be differentially expressed under drought, 97 genes were common in both the genotypes. These included the upregulated genes, such as probable mannitol dehydrogenase, serine hydroxymethyltransferase 4-like, 17.5 kDa class I heat shock protein-like, cytochrome P450 81E8-like, and galactinol-sucrose galactosyltransferase-like, and downregulated genes, such as probable xyloglucan endotransglucosylase/hydrolase protein 23, abscisic acid 8′-hydroxylase 1-like, Calmodulin-like protein 11, and proline dehydrogenase 2 mitochondrial-like genes. A major finding was the involvement of transcription factors, including AP2-EREBP, bHLH, bZIP, C3H, MYB, NAC, WRKY, and MADS. The present study is the first comparative analysis of RNA-Seq data for two drought-tolerant chickpea genotypes. These findings would help in improving drought tolerance across chickpea genotypes.
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.
Beneficial soil microorganisms largely comprise of plant growth-promoting rhizobacteria (PGPR), which adhere to plant roots and facilitate their growth and development.
(RA) strain MTCC5279 is one ...such PGPR that exhibits several characteristics of plant growth promotion, such as P-solubilization, and siderophores and IAA production. Plant-PGPR interactions are very complex phenomena, and essentially modulate the expression of numerous genes, consequently leading to changes in the physiological, biochemical, cellular and molecular responses of plants. Therefore, in order to understand the molecular bases of plant-PGPR interactions, we carried out the identification of microRNAs from the roots of
upon
RA-inoculation, and analyses of their expression. MicroRNAs (miRNAs) are 20- to 24-nt non-coding small RNAs known to regulate the expression of their target genes. Small RNA sequencing led to the identification of 293 known and 67 putative novel miRNAs, from the control and RA-inoculated libraries. Among these, 15 known miRNAs showed differential expression upon RA-inoculation in comparison to the control, and their expressions were corroborated by stem-loop quantitative real-time PCR. Overall, 28,746 and 6931 mRNAs were expected to be the targets of the known and putative novel miRNAs, respectively, which take part in numerous biological, cellular and molecular processes. An inverse correlation between the expression of RA-responsive miRNAs and their target genes also strengthened the crucial role of RA in developmental regulation. Our results offer insights into the understanding of the RA-mediated modulation of miRNAs and their targets in
, and pave the way for the further exploitation and characterization of candidate RA-responsive miRNA(s) for various crop improvement strategies directed towards plant sustainable growth and development.
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.
Multiple plant growth-promoting attributes with N-acyl homoserine lactone (AHL)-mediated quorum sensing exhibiting bacterial strains can help plants to withstand varying abiotic and biotic stress ...conditions for improving the plant health and productivity. In total, 306 bacterial isolates were isolated from diverse locations and sites. In our exploration, bacterial isolates were screened based on AHL production, plant growth-promoting attributes, abiotic stress tolerance, and antagonistic activity against phytopathogenic fungi. Among the screened 306 isolates, 4 (11VPKHP4, 7VP51.8, P51.10, NBRI N7) were selected based on their efficiency in AHL production, biofilm formation, enduring different abiotic stress conditions, exhibiting plant growth-promoting attributes, and antagonistic activity. Based on 16S rRNA gene sequencing analyses of the selected 4 isolates belong to Pseudomonas genera. Selected isolates 11VPKHP4, 7VP51.8, P51.10, and NBRI N7 were also proficient in biosurfactant production, emulsification, suggesting that all isolates fabricate emulsifiers. The plant growth promotion potential of selected 4 bacterial isolates showed significant growth enhancement in all the vegetative parameters of Zea mays under control as well as drought stress condition. Biochemical parameters and defense enzymes under drought stress conditions were also modulated in the PGPR treated plants as compared to their uninoculated respective controls. With quorum sensing, multiple PGPR attributes, stress tolerance, biofilm formation, and EPS production the selected isolates have the potential to facilitate enhanced plant growth, rhizosphere colonization, maintenance of soil moisture content under normal and diverse stresses.
Summary
Plant growth promotion by microbes is a cumulative phenomenon involving multiple traits, many of which are not explored yet. Hence, to unravel microbial mechanisms underlying growth ...promotion, we have analysed the genomes of two potential growth‐promoting microbes, viz., Pseudomonas sp. CK‐NBRI‐02 (P2) and Bacillus marisflavi CK‐NBRI‐03 (P3) for the presence of plant‐beneficial traits. Besides known traits, we found that microbes differ in their ability to metabolize methylglyoxal (MG), a ubiquitous cytotoxin regarded as general consequence of stress in plants. P2 exhibited greater tolerance to MG and possessed better ability to sustain plant growth under dicarbonyl stress. However, under salinity, only P3 showed a dose‐dependent induction in MG detoxification activity in accordance with concomitant increase in MG levels, contributing to enhanced salt tolerance. Furthermore, salt‐stressed transcriptomes of both the strains showed differences with respect to MG, ion and osmolyte homeostasis, with P3 being more responsive to stress. Importantly, application of either strain altered MG levels and subsequently MG detoxification machinery in Arabidopsis, probably to strengthen plant defence response and growth. We therefore, suggest a crucial role of microbial MG resistance in plant growth promotion and that it should be considered as a beneficial trait while screening microbes for stress mitigation in plants.
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