Several anthropogenic activities including mining, modern agricultural practices, and industrialization have long-term detrimental effect on our environment. All these factors lead to increase in ...heavy metal concentration in soil, water, and air. Soil contamination with heavy metals cause several environmental problems and imparts toxic effect on plant as well as animals. In response to these adverse conditions, plants evolve complex molecular and physiological mechanisms for better adaptability, tolerance, and survival. Nowadays conventional breeding and transgenic technology are being used for development of metal stress resistant varieties which, however, are time consuming and labor intensive. Interestingly the use of microbes as an alternate technology for improving metal tolerance of plants is gaining momentum recently. The use of these beneficial microorganisms is considered as one of the most promising methods for safe crop-management practices. Interaction of plants with soil microorganisms can play a vital role in acclimatizing plants to metalliferous environments, and can thus be explored to improve microbe-assisted metal tolerance. Plant-associated microbes decrease metal accumulation in plant tissues and also help to reduce metal bioavailability in soil through various mechanisms. Nowadays, a novel phytobacterial strategy, i.e., genetically transformed bacteria has been used to increase remediation of heavy metals and stress tolerance in plants. This review takes into account our current state of knowledge of the harmful effects of heavy metal stress, the signaling responses to metal stress, and the role of plant-associated microbes in metal stress tolerance. The review also highlights the challenges and opportunities in this continued area of research on plant-microbe-metal interaction.
Here, MoS2/rGO as a co-catalyst with Cu2O to suppress the recombination rate of the photogenerated charge carrier in Cu2O as well as to inhibit the photocorrosion and provide an electron rich ...environment to the system. The ternary composite shows higher photoactivity as compared with the bare one. The photoelectrochemical activity of the bare photocatalyst was 0.33 mA cm−2 while the photoelectrochemical activity of the ternary composite Cu2O-MoS2/rGO was 8.46 mA cm−2 which is 26 times higher photoactivity than the bare photocatalyst. Transient photocurrent response measurement provides the stability information of the photocatalysts.
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•Cost effective, non-toxic, and stable photo-catalyst Cu2O-MoS2/rGO.•Combination of MoS2/rGO with Cu2O makes more attractive towards PEC applications.•Photoelectrochemical activity of Cu2O-MoS2/rGO is 26 times higher than the bare Cu2O.•.Transient photocurrent response revealed the stability of the photocatalyst.
Solar to hydrogen conversion using photocatalyst is one of the most promising methods to get a pollution free and sustainable fuel. Most of the photocatalysts suffer with major problems like, charge recombination and photocorrosion, which diminishes their practical application. The need is to obtain a stable photocatalyst where the photocorrosion is inhibited. Cu2O has been used as a photocatalyst and it holds promise being non-toxic and abundantly available on earth. However, due to lower band edge of Cu2O, it gets oxidized easily and its high recombination rate of electron-hole pairs which lowers its activity. For the inhibition of the photocorrosion, there is a need of a passivation layer that protects the photocatalyst by blocking the unfavorable reaction which causes photocorrosion. Here, we have used MoS2/rGO as a co-catalyst with Cu2O to suppress the recombination rate of the photogenerated charge carrier in Cu2O as well as to inhibit the photocorrosion and provide an electron rich environment to the system. The ternary composite shows higher photoactivity as compared with the bare one. The photoelectrochemical activity of the bare photocatalyst was 0.33 mA cm−2 while the photoelectrochemical activity of the ternary composite Cu2O-MoS2/rGO was 8.46 mA cm−2 at 0.95 V. Transient photocurrent response measurement provides the stability information of the photocatalysts.
Being sessile in nature, plants have to withstand various adverse environmental stress conditions including both biotic and abiotic stresses. Comparatively, abiotic stresses such as drought, ...salinity, high temperature, and cold pose major threat to agriculture by negatively impacting plant growth and yield worldwide. Rice is one of the most widely consumed staple cereals across the globe, the production and productivity of which is also severely affected by different abiotic stresses. Therefore, several crop improvement programs are directed toward developing stress tolerant rice cultivars either through marker assisted breeding or transgenic technology. Alternatively, some known rhizospheric competent bacteria are also known to improve plant growth during abiotic stresses. A plant growth promoting rhizobacteria (PGPR),
NBRI-SN13 (SN13) was previously reported by our lab to confer salt stress tolerance to rice seedlings. However, the present study investigates the role of SN13 in ameliorating various abiotic stresses such as salt, drought, desiccation, heat, cold, and freezing on a popular rice cv. Saryu-52 under hydroponic growth conditions. Apart from this, seedlings were also exogenously supplied with abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA) and ethephon (ET) to study the role of SN13 in phytohormone-induced stress tolerance as well as its role in abiotic and biotic stress cross-talk. All abiotic stresses and phytohormone treatments significantly affected various physiological and biochemical parameters like membrane integrity and osmolyte accumulation. SN13 also positively modulated stress-responsive gene expressions under various abiotic stresses and phytohormone treatments suggesting its multifaceted role in cross-talk among stresses and phytohormones in response to PGPR. To the best of our knowledge, this is the first report on detailed analysis of plant growth promotion and stress alleviation by a PGPR in rice seedlings subjected to various abiotic stresses and phytohormone treatments for 0, 1, 3, 10, and 24 h.
Soil salinity, a growing issue worldwide, is a detrimental consequence of the ever-changing climate, which has highlighted and worsened the conditions associated with damaged soil quality, reduced ...agricultural production, and decreasing land areas, thus resulting in an unsteady national economy. In this review, halo-tolerant plant growth-promoting rhizo-microbiomes (PGPRs) are evaluated in the salinity-affected agriculture as they serve as excellent agents in controlling various biotic-abiotic stresses and help in the augmentation of crop productivity. Integrated efforts of these effective microbes lighten the load of agro-chemicals on the environment while managing nutrient availability. PGPR-assisted modern agriculture practices have emerged as a green strategy to benefit sustainable farming without compromising the crop yield under salinity as well as salinity-affected supplementary stresses including increased temperature, drought, salinity, and potential invasive plant pathogenicity. PGPRs as bio-inoculants impart induced systemic tolerance (IST) to plants by the production of volatile organic compounds (VOCs), antioxidants, osmolytes, extracellular polymeric substances (EPS), phytohormones, and ACC-deaminase and recuperation of nutritional status and ionic homeostasis. Regulation of PGPR-induced signaling pathways such as MAPK and CDPK assists in salinity stress alleviation. The "Next Gen Agriculture" consists of the application of designer crop microbiomes through gene editing tools, for instance, CRISPR, and engineering of the metabolic pathways of the microbes so as to gain maximum plant resistance. The utilization of omics technologies over the traditional approaches can fulfill the criteria required to increase crop yields in a sustainable manner for feeding the burgeoning population and augment plant adaptability under climate change conditions, ultimately leading to improved vitality. Furthermore, constraints such as the crop specificity issue of PGPR, lack of acceptance by farmers, and legal regulatory aspects have been acknowledged while also discussing the future trends for product commercialization with the view of the changing climate.
Key message
Overexpression of
Withania somnifera
SGT gene (
WssgtL3.1)
in transgenic
Arabidopsis
improves various agronomic and physiological traits and alters conjugated sterol levels to mitigate ...the effect of salt stress.
Sterols are essential constituents of cell membranes that are involved in several biological functions, including response to various biotic and abiotic stresses by altering membrane permeability and signaling pathways. Sterol glycosyltransferases (SGTs) are enzymes that are involved in sterol modification by converting sterols into sterol-conjugates to play essential roles in adaptive responses. However, their roles under abiotic stresses are lesser-known. Among abiotic stresses, salinity imposes serious threat to crop yield worldwide, hence the present study intends to investigate the role of
WssgtL3.1
-overexpressed
Arabidopsis
plants under salt stress indicating the crosstalk between
SGT
gene and salinity to develop improved crop varieties with better stress tolerance ability. The findings revealed that overexpression of
WssgtL3.1
gene in
A. thaliana
improved the resistance against salt stress in the overexpressing lines. Transgenic lines showed significantly higher germination rate, increased plant growth with less chlorophyll damage compared to wild-type (WT) control plants. Moreover, better tolerance also correlated with enhanced osmolytes (proline and soluble sugar), better membrane integrity, decreased H
2
O
2
production and lesser MDA accumulation and Na
+
/K
+
ratio with more negative osmotic potential in overexpressed lines. Additionally, in sterol profiling, significant enhancement in stigmasterol was also observed in transgenic lines than WT plants. Furthermore, in expression profiling, salt responsive genes
LEA 4–5
,
sucrose synthase
, and transporter of monosaccharide (
ERD
) significantly upregulated in overexpressing lines as compared to WT. Thus our data strongly support the defensive role of
Withania somnifera SGT
gene (
WssgtL3.1
) against salt stress and contribute to improved salinity tolerance in plants through sterol modulation.
Soil salinity diminishes soil health and reduces crop yield, which is becoming a major global concern. Salinity stress is one of the primary stresses, leading to several other secondary stresses that ...restrict plant growth and soil fertility. The major secondary stresses induced in plants under saline-alkaline conditions include osmotic stress, nutrient limitation, and ionic stress, all of which negatively impact overall plant growth. Under stressed conditions, certain beneficial soil microflora are known to have evolved phytostimulating mechanisms, such as the synthesis of osmoprotectants, siderophores, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, phosphate solubilization, and hormone production, which enhance plant growth and development while mitigating nutrient stress. Beneficial soil-borne bacterial species such as Bacillus, Pseudomonas, and Klebsiella and fungal strains such as Trichoderma, Aspergillus, Penicillium, Alternaria, and Fusarium also aid in reducing salinity stress. Phosphate-solubilizing microorganisms also assist in nutrient acquisition via both enzymatic and non-enzymatic processes. In the case of enzymatic processes, they produce different enzymes such as alkaline phosphatases and phytases, whereas non-enzymatic processes produce organic acids such as gluconic, citric, malic, and oxalic acids. The native halotolerant/halophilic soil microbial gene pool with multifunctional traits and stress-induced gene expression can be developed as suitable bio-inoculants to enhance stress tolerance and optimize plant growth in saline soils.
Abstract
Over the past decade, long non-coding RNA (lncRNA), which lacks protein-coding potential, has emerged as an essential regulator of the genome. The present study examined 13,599 lncRNAs in
...Arabidopsis thaliana
, 11,565 in
Oryza sativa
, and 32,397 in
Zea mays
for their characteristic features and explored the associated genomic and epigenomic features. We found lncRNAs were distributed throughout the chromosomes and the Helitron family of transposable elements (TEs) enriched, while the terminal inverted repeat depleted in lncRNA transcribing regions. Our analyses determined that lncRNA transcribing regions show rare or weak signals for most epigenetic marks except for H3K9me2 and cytosine methylation in all three plant species. LncRNAs showed preferential localization in the nucleus and cytoplasm; however, the distribution ratio in the cytoplasm and nucleus varies among the studied plant species. We identified several conserved endogenous target mimic sites in the lncRNAs among the studied plants. We found 233, 301, and 273 unique miRNAs, potentially targeting the lncRNAs of
A. thaliana
,
O. sativa
, and
Z. mays
, respectively. Our study has revealed that miRNAs, which interact with lncRNAs, target genes that are involved in a diverse array of biological and molecular processes. The miRNA-targeted lncRNAs displayed a strong affinity for several transcription factors, including ERF and BBR-BPC, mutually present in all three plants, advocating their conserved functions. Overall, the present study showed that plant lncRNAs exhibit conserved genomic and epigenomic characteristics and potentially govern the growth and development of plants.
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.
Key message
Overexpression of
Bacillus amyloliquefaciens
SN13-responsive
OsNAM
gene in
Arabidopsis
reveals its important role in beneficial plant and plant growth promoting rhizobacteria interaction ...by conferring stress tolerance and phytohormone modulation.
Salinity is one of the major constraints that affect crop development and yield. Plants respond and adapt to salt stress via complex mechanisms that involve morpho-physiological, biochemical, and molecular changes. The expression of numerous genes is known to alter during various abiotic stresses and impart stress tolerance. Recently, some known rhizospheric microbes have also been used to mitigate the effects of abiotic stresses; however, the molecular basis of such interactions remains elusive. Therefore, the present investigation was aimed to elucidate the plant growth-promoting rhizobacteria (PGPR;
Bacillus amyloliquefaciens
-SN13) -induced crosstalk among salinity and phytohormones in
OsNAM
-overexpressed
Arabidopsis
plants. Transgenic plants showed increased germination percentage compared to wild-type (WT) seeds under 100 mM of NaCl. Phenotypic data showed increased root length, rosette diameter, leaf size, and biomass in transgenics than WT plants. Transgenic plants can also better maintain membrane integrity and osmolyte concentration under salinity as compared to WT. Further, gene expression analysis of
AP2/ERF, GST, ERD4
, and
ARF2
genes showed differential expression and their positive modulation in transgenic
Arabidopsis
exposed to salt stress in the presence of SN13 as compared to uninoculated WT. Modulation in IAA, ABA, and GA content in inoculated plants showed the more pronounced positive effects of SN13 on transgenic plants that supported our findings on
Arabidopsis
–SN13 interaction. Overall, the study concludes that SN13 positively modulated expression of stress-responsive genes under salinity and alter phytohormones levels in
OsNAM
-overexpressed plants suggesting its extensive role in cross-talk among salinity and phytohormones in response to PGPR.
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