Early-responsive molecular signatures associated with halophytic adaptation in Sesuvium portulacastrum (L.).

Sesuvium portulacastrum (L.) is a halophyte, adapted to grow naturally under saline environments. The ability to use Na and K interchangeably indicated its facultative halophyte nature. No significant growth reduction occurs in seedlings up to 250 mM NaCl, except for curling of the youngest leaf. Within 8 h of salt treatment, seedlings accumulate proline, glycine betaine and other amino acids in both root and shoot. Despite a continued increase of tissue Na content, the number of differentially expressed genes (DEGs) decreases between 8 and 24 h of salt exposure, indicating transcriptional restoration after the initial osmotic challenge. At 8 h, upregulated genes mainly encode transporters and transcription factors, while genes in growth-related pathways such as photosynthesis and ribosome-associated biogenesis are suppressed. Overexpression of SpRAB18 (an ABA-responsive dehydrin), one of the most strongly induced DEGs, in soybean was found to increase biomass in control conditions and the growth benefit was maintained when plants were grown in 100 mM NaCl, indicating conservation of function in halophyte and glycophyte. An open-access transcriptome database "SesuviumKB" (https://cb.imsc.res.in/sesuviumkb/) was developed to involve the scientific community in wide-scale functional studies of S. portulacastrum genes, that could pave the way to engineer salt tolerance in crops.

CIPK9 targets VDAC3 and modulates oxidative stress responses in Arabidopsis.

Calcium (Ca2+ ) is widely recognized as a key second messenger in mediating various plant adaptive responses. Here we show that calcineurin B-like interacting protein kinase CIPK9 along with its interacting partner VDAC3 identified in the present study are involved in mediating plant responses to methyl viologen (MV). CIPK9 physically interacts with and phosphorylates VDAC3. Co-localization, co-immunoprecipitation, and fluorescence resonance energy transfer experiments proved their physical interaction in planta. Both cipk9 and vdac3 mutants exhibited a tolerant phenotype against MV-induced oxidative stress, which coincided with the lower-level accumulation of reactive oxygen species in their roots. In addition, the analysis of cipk9vdac3 double mutant and VDAC3 overexpressing plants revealed that CIPK9 and VDAC3 were involved in the same pathway for inducing MV-dependent oxidative stress. The response to MV was suppressed by the addition of lanthanum chloride, a non-specific Ca2+ channel blocker indicating the role of Ca2+ in this pathway. Our study suggest that CIPK9-VDAC3 module may act as a key component in mediating oxidative stress responses in Arabidopsis.

Profiling of conserved orthologs and miRNAs for understanding their role in salt tolerance mechanism of Sesuvium portulacastrum L.

BACKGROUND: Sesuvium portulacastrum is a facultative halophyte capable of thriving in a saline environment. Despite molecular studies conducted to unravel its salt adaptation mechanism, there is a paucity of information on the role of salt-responsive orthologs and microRNAs (miRNAs) in this halophyte. Here, we searched the orthology to identify salt-responsive orthologs and miRNA targets of Sesuvium using the Arabidopsis genome. METHODS: The relative fold change of orthologs, conserved miRNAs, and miRNA targets of Sesuvium was analyzed under 100 mM (LS) and 250 mM NaCl (HS) treatment at 24 h using qRT-PCR. The comparison between the expression of Sesuvium orthologs and Arabidopsis orthologs (Arabidopsis eFP browser database) was used to identify differentially expressed genes. RESULTS: Upon salt treatment, we found that SpCIPK3 (1.95-fold in LS and 2.90-fold in HS) in Sesuvium roots, and SpNHX7 (1.61-fold in LS and 6.39-fold in HS) and, SpSTPK2 (2.54-fold in LS and 7.65-fold in HS) in Sesuvium leaves were upregulated in a salt concentration-specific manner. In Arabidopsis, these genes were either downregulated or did not show significant variation, implicating its significance in the halophytic nature of Sesuvium. Furthermore, miRNAs like miR394a, miR396a, and miR397a exhibited a negative correlation with their targets-Frigida interacting protein 1, Cysteine proteinases superfamily protein, and Putative laccase, respectively under different salt treatments. CONCLUSION: The study revealed that the high salt tolerance in Sesuvium is associated with distinct transcriptional reprogramming, hence, to gain holistic mechanistic insights, global-scale profiling is required.

Prospects of advanced metagenomics and meta-omics in the investigation of phytomicrobiome to forecast beneficial and pathogenic response.

Microorganisms dwell in diverse plant niches as non-axenic biotic components that are beneficial as well pathogenic for the host. They improve nutrients-uptake, stress tolerance, phytohormone synthesis, and strengthening the defense system through phyllosphere, rhizosphere, and endosphere. The negative consequences of the microbial communities are largely in the form of diseases characterized by certain symptoms such as gall, cankers, rots etc. Uncultivable and unspecified nature of different phytomicrobiomes communities is a challenge in the management of plant disease, a leading cause for the loss of the plant products. Metagenomics has opened a new gateway for the exploration of microorganisms that are hitherto unknown, enables investigation of the functional aspect of microbial gene products through metatranscriptomics and metabolomics. Metagenomics offers advantages of characterizing previously unknown microorganisms from extreme environments like hot springs, glaciers, deep seas, animal gut etc. besides bioprospecting gene products such as Taq polymerase, bor encoded indolotryptoline, hydrolases, and polyketides. This review provides a detailed account of the phytomicrobiome networks and highlights the importance and limitations of metagenomics and other meta-omics approaches for the understanding of plant microbial diversity with special focus on the disease control and its management.

Molecular insights into sensing, regulation and improving of heat tolerance in plants.

Climate-change-mediated increase in temperature extremes has become a threat to plant productivity. Heat stress-induced changes in growth pattern, sensitivity to pests, plant phonologies, flowering, shrinkage of maturity period, grain filling, and increased senescence result in significant yield losses. Heat stress triggers multitude of cellular, physiological and molecular responses in plants beginning from the early sensing followed by signal transduction, osmolyte synthesis, antioxidant defense, and heat stress-associated gene expression. Several genes and metabolites involved in heat perception and in the adaptation response have been isolated and characterized in plants. Heat stress responses are also regulated by the heat stress transcription factors (HSFs), miRNAs and transcriptional factors which together form another layer of regulatory circuit. With the availability of functionally validated candidate genes, transgenic approaches have been applied for developing heat-tolerant transgenic maize, tobacco and sweet potato. In this review, we present an account of molecular mechanisms of heat tolerance and discuss the current developments in genetic manipulation for heat tolerant crops for future sustainable agriculture.

Unlocking Allelic Diversity for Sustainable Development of Salinity Stress Tolerance in Rice.

Rice is a major cereal crop, negatively impacted by soil-salinity, both in terms of plant growth as well as productivity. Salinity tolerant rice varieties have been developed using conventional breeding approaches, however, there has been limited success which is primarily due to the complexity of the trait, low yield, variable salt stress response and availability of genetic resources. Furthermore, the narrow genetic base is a hindrance for further improvement of the rice varieties. Therefore, there is a greater need to screen available donor germplasm in rice for salinity tolerance related genes and traits. In this regard, genomics based techniques are useful for exploring new gene resources and QTLs. In rice, the vast allelic diversity existing in the wild and cultivated germplasm needs to be explored for improving salt tolerance. In the present review, we provide an overview of the allelic diversity in the Quantitative Trait Loci (QTLs) like Saltol, qGR6.2, qSE3 and RNC4 as well as genes like OsHKT1;1, SKC1 (OsHKT1;5/HKT8) and OsSTL1 (salt tolerance level 1 gene) related to salt tolerance in rice. We have also discussed approaches for developing salt-tolerant cultivars by utilizing the effective QTLs or genes/alleles in rice.

Engineering Resistance Against Viruses in Field Crops Using CRISPR- Cas9.

Food security is threatened by various biotic stresses that affect the growth and production of agricultural crops. Viral diseases have become a serious concern for crop plants as they incur huge yield losses. The enhancement of host resistance against plant viruses is a priority for the effective management of plant viral diseases. However, in the present context of the climate change scenario, plant viruses are rapidly evolving, resulting in the loss of the host resistance mechanism. Advances in genome editing techniques, such as CRISPR-Cas9 [clustered regularly interspaced palindromic repeats-CRISPR-associated 9], have been recognized as promising tools for the development of plant virus resistance. CRISPR-Cas9 genome editing tool is widely preferred due to high target specificity, simplicity, efficiency, and reproducibility. CRISPR-Cas9 based virus resistance in plants has been successfully achieved by gene targeting and cleaving the viral genome or altering the plant genome to enhance plant innate immunity. In this article, we have described the CRISPR-Cas9 system, mechanism of plant immunity against viruses and highlighted the use of the CRISPR-Cas9 system to engineer virus resistance in plants. We also discussed prospects and challenges on the use of CRISPR-Cas9-mediated plant virus resistance in crop improvement.

Engineering salinity tolerance in plants: progress and prospects.

MAIN CONCLUSION: There is a need to integrate conceptual framework based on the current understanding of salt stress responses with different approaches for manipulating and improving salt tolerance in crop plants. Soil salinity exerts significant constraints on global crop production, posing a serious challenge for plant breeders and biotechnologists. The classical transgenic approach for enhancing salinity tolerance in plants revolves by boosting endogenous defence mechanisms, often via a single-gene approach, and usually involves the enhanced synthesis of compatible osmolytes, antioxidants, polyamines, maintenance of hormone homeostasis, modification of transporters and/or regulatory proteins, including transcription factors and alternative splicing events. Occasionally, genetic manipulation of regulatory proteins or phytohormone levels confers salinity tolerance, but all these may cause undesired reduction in plant growth and/or yields. In this review, we present and evaluate novel and cutting-edge approaches for engineering salt tolerance in crop plants. First, we cover recent findings regarding the importance of regulatory proteins and transporters, and how they can be used to enhance salt tolerance in crop plants. We also evaluate the importance of halobiomes as a reservoir of genes that can be used for engineering salt tolerance in glycophytic crops. Additionally, the role of microRNAs as critical post-transcriptional regulators in plant adaptive responses to salt stress is reviewed and their use for engineering salt-tolerant crop plants is critically assessed. The potentials of alternative splicing mechanisms and targeted gene-editing technologies in understanding plant salt stress responses and developing salt-tolerant crop plants are also discussed.

Emerging concepts of potassium homeostasis in plants.

Potassium (K+) is an essential cation in all organisms that influences crop production and ecosystem stability. Although most soils are rich in K minerals, relatively little K+ is present in forms that are available to plants. Moreover, leaching and run-off from the upper soil layers contribute to K+ deficiencies in agricultural soils. Hence, the demand for K fertilizer is increasing worldwide. K+ regulates multiple processes in cells and organs, with K+ deficiency resulting in decreased plant growth and productivity. Here, we discuss the complexity of the reactive oxygen species-calcium-hormone signalling network that is responsible for the sensing of K+ deficiency in plants, together with genetic approaches using K+ transporters that have been used to increase K+ use efficiency (KUE) in plants, particularly under environmental stress conditions such as salinity and heavy metal contamination. Publicly available rice transcriptome data are used to demonstrate the two-way relationship between K+ and nitrogen nutrition, highlighting how each nutrient can regulate the uptake and root to shoot translocation of the other. Future research directions are discussed in terms of this relationship, as well as prospects for molecular approaches for the generation of improved varieties and the implementation of new agronomic practices. An increased knowledge of the systems that sense and take up K+, and their regulation, will not only improve current understanding of plant K+ homeostasis but also facilitate new research and the implementation of measures to improve plant KUE for sustainable food production.

Transcriptional reprogramming and enhanced photosynthesis drive inducible salt tolerance in sugarcane mutant line M4209.

Sugarcane (Saccharum officinarum) is a globally cultivated cash crop whose yield is negatively affected by soil salinity. In this study, we investigated the molecular basis of inducible salt tolerance in M4209, a sugarcane mutant line generated through radiation-induced mutagenesis. Under salt-contaminated field conditions, M4209 exhibited 32% higher cane yield as compared with its salt-sensitive parent, Co86032. In pot experiments, post-sprouting phenotyping indicated that M4209 had significantly greater leaf biomass compared with Co86032 under treatment with 50 mM and 200 mM NaCl. This was concomitant with M4209 having 1.9-fold and 1.6-fold higher K+/Na+ ratios, and 4-fold and 40-fold higher glutathione reductase activities in 50 mM and 200 mM NaCl, respectively, which suggested that it had better ionic and redox homeostasis than Co86032. Transcriptome profiling using RNA-seq indicated an extensive reprograming of stress-responsive modules associated with photosynthesis, transmembrane transport, and metabolic processes in M4209 under 50 mM NaCl stress. Using ranking analysis, we identified Phenylalanine Ammonia Lyase (PAL), Acyl-Transferase Like (ATL), and Salt-Activated Transcriptional Activator (SATA) as the genes most associated with salt tolerance in M4209. M4209 also exhibited photosynthetic rates that were 3-4-fold higher than those of Co86032 under NaCl stress conditions. Our results highlight the significance of transcriptional reprogramming coupled with improved photosynthetic efficiency in determining salt tolerance in sugarcane.

VDAC and its interacting partners in plant and animal systems: an overview.

Molecular trafficking between different subcellular compartments is the key for normal cellular functioning. Voltage-dependent anion channels (VDACs) are small-sized proteins present in the outer mitochondrial membrane, which mediate molecular trafficking between mitochondria and cytoplasm. The conductivity of VDAC is dependent on the transmembrane voltage, its oligomeric state and membrane lipids. VDAC acts as a convergence point to a diverse variety of mitochondrial functions as well as cell survival. This functional diversity is attained due to their interaction with a plethora of proteins inside the cell. Although, there are hints toward functional conservation/divergence between animals and plants; knowledge about the functional role of the VDACs in plants is still limited. We present here a comparative overview to provide an integrative picture of the interactions of VDAC with different proteins in both animals and plants. Also discussed are their physiological functions from the perspective of cellular movements, signal transduction, cellular fate, disease and development. This in-depth knowledge of the biological importance of VDAC and its interacting partner(s) will assist us to explore their function in the applied context in both plant and animal.

Cellular and Subcellular Phosphate Transport Machinery in Plants.

Phosphorus (P) is an essential element required for incorporation into several biomolecules and for various biological functions; it is, therefore, vital for optimal growth and development of plants. The extensive research on identifying the processes underlying the uptake, transport, and homeostasis of phosphate (Pi) in various plant organs yielded valuable information. The transport of Pi occurs from the soil into root epidermal cells, followed by loading into the root xylem vessels for distribution into other plant organs. Under conditions of Pi deficiency, Pi is also translocated from the shoot to the root via the phloem. Vacuoles act as a storage pool for extra Pi, enabling its delivery to the cytosol, a process which plays an important role in the homeostatic control of cytoplasmic Pi levels. In mitochondria and chloroplasts, Pi homeostasis regulates ATP synthase activity to maintain optimal ATP levels. Additionally, the endoplasmic reticulum functions to direct Pi transporters and Pi toward various locations. The intracellular membrane potential and pH in the subcellular organelles could also play an important role in the kinetics of Pi transport. The presented review provides an overview of Pi transport mechanisms in subcellular organelles, and also discusses how they affect Pi balancing at cellular, tissue, and whole-plant levels.

Genomics of Metal Stress-Mediated Signalling and Plant Adaptive Responses in Reference to Phytohormones.

INTRODUCTION: As a consequence of a sessile lifestyle, plants often have to face a number of life threatening abiotic and biotic stresses. Plants counteract the stresses through morphological and physiological adaptations, which are imparted through flexible and well-coordinated network of signalling and effector molecules, where phytohormones play important role. Hormone synthesis, signal transduction, perception and cross-talks create a complex network. Omics approaches, which include transcriptomics, genomics, proteomics and metabolomics, have opened new paths to understand such complex networks. OBJECTIVE: This review concentrates on the importance of phytohormones and enzymatic expressions under metal stressed conditions. CONCLUSION: This review sheds light on gene expressions involved in plant adaptive and defence responses during metal stress. It gives an insight of genomic approaches leading to identification and functional annotation of genes involved in phytohormone signal transduction and perception. Moreover, it also emphasizes on perception, signalling and cross-talks among various phytohormones and other signalling components viz., Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS).

Arsenic stress affects the expression profile of genes of 14-3-3 proteins in the shoot of mycorrhiza colonized rice.

The intimate association between the arbuscular mycorrhizal fungi and host plants helps the latter in phosphate acquisition in exchange of carbohydrates and in enhanced stress tolerance. Similarly, the ubiquitous 14-3-3 protein family is known to be a major regulator of plant metabolism and stress responses. However, the involvement of mycorrhiza and plant 14-3-3 proteins interaction in plant response to environmental stimuli, such as arsenic (As) stress, is yet unknown. In this study, we analysed the impact of the As stress on the expression profile of 14-3-3 genes in the shoot of mycorrhiza colonized rice (Oryza sativa) plants. Ten day old rice seedlings were kept for 45 days for mycorrhizal colonisation (10 g inoculum per 120 g soilrite) and were then subjected to 12.5 µM arsenate [As(V)] exposure for 1 and 3 days, in hydroponics. Arsenate stress resulted in significant change in expression of 14-3-3 protein genes in non-colonized and mycorrhiza colonized rice plants which indicated As mediated effects on 14-3-3 proteins as well as interactive impact of mycorrhiza colonization. Indeed, mycorrhiza colonization itself induced up-regulation of all 14-3-3 genes in the absence of As stress. The results thus indicate that 14-3-3 proteins might be involved in As stress signalling and the mycorrhiza induced As stress response of the rice plants.

Overexpression of OsTIP1;2 confers arsenite tolerance in rice and reduces root-to-shoot translocation of arsenic.

Tonoplast Intrinsic Proteins (TIPs) are vital in transporting water and solutes across vacuolar membrane. The role of TIPs in the arsenic stress response is largely undefined. Rice shows sensitivity to the arsenite [As[III]] stress and its accumulation at high concentrations in grains poses severe health hazards. In this study, functional characterization of OsTIP1;2 from Oryza sativa indica cultivar Pusa Basmati-1 (PB-1) was done under the As[III] stress. Overexpression of OsTIP1;2 in PB-1 rice conferred tolerance to As[III] treatment measured in terms of enhanced shoot growth, biomass, and shoot/root ratio of overexpression (OE) lines compared to the wild-type (WT) plants. Moreover, seed priming with the IRW100 yeast cells (deficient in vacuolar membrane As[III] transporter YCF1) expressing OsTIP1;2 further increased As[III] stress tolerance of both WT and OE plants. The dithizone assay showed that WT plants accumulated high arsenic in shoots, while OE lines accumulated more arsenic in roots than shoots thereby limiting the translocation of arsenic to shoot. The activity of enzymatic and non-enzymatic antioxidants also increased in the OE lines on exposure to As[III]. The tissue-specific localization showed OsTIP1;2 promoter activity in root and root hairs, indicating its possible root-specific function. After As[III] treatment in hydroponic medium, the arsenic translocation factor (TF) for WT was around 0.8, while that of OE lines was around 0.2. Moreover, the arsenic content in the grains of OE lines reduced significantly compared to WT plants.

Chromiomics: Chromium detoxification and approaches for engineering tolerance in plants.

Chromium (Cr) is a heavy metal that poses a grave threat to the ecosystem including plants. Chromium is very harmful to plants due to its effects on many physiological and metabolic pathways culminating in a negative impact on plant's growth, development, and ability to take up nutrients. Plants have developed physiological, biochemical, and molecular ways of defense against Cr, such as by augmenting antioxidant potential to reduce reactive oxygen species (ROS). A number of genes have been discovered to play a significant role in the defense mechanisms of plants against Cr, for example, genes associated with the activation of phytochelatins, metallothioneins, and those of enzymes like glutathione-S-transferases. Along with this, a few miRNAs have been found to be associated in alleviating Cr stress and, to augment plant tolerance by controlling transcription factors, HSPs, and the expression of a few proteins and hormones. Defense pathway genes and miRNAs have been used for the generation of transgenic phytoremediator plants. Not only do the transgenic plants have a higher tolerance to Cr, but they also act as hyperaccumulators for Cr and have the potential to remediate other heavy metals. This article describes about environmental Cr contamination, Cr effects on plants, different genes and miRNAs involved in Cr stress mitigation and use of candidate genes, microRNAs for creating transgenic plant systems for phytoremediation, and the applications of CRISPR technology. It is expected that the integration of omics approach and advanced genomics will offer scope for more effective phytoremediation of Chromium in the coming years.

Antioxidant Defense and Ionic Homeostasis Govern Stage-Specific Response of Salinity Stress in Contrasting Rice Varieties.

Salt stress is one of the most severe environmental stresses limiting the productivity of crops, including rice. However, there is a lack of information on how salt-stress sensitivity varies across different developmental stages in rice. In view of this, a comparative evaluation of contrasting rice varieties CSR36 (salt tolerant) and Jaya (salt sensitive) was conducted, wherein NaCl stress (50 mM) was independently given either at seedling (S-stage), tillering (T-stage), flowering (F-stage), seed-setting (SS-stage) or throughout plant growth, from seedling till maturity. Except for S-stage, CSR36 exhibited improved NaCl stress tolerance than Jaya, at all other tested stages. Principal component analysis (PCA) revealed that the improved NaCl stress tolerance in CSR36 coincided with enhanced activities/levels of enzymatic/non-enzymatic antioxidants (root ascorbate peroxidase for T- (2.74-fold) and S+T- (2.12-fold) stages and root catalase for F- (5.22-fold), S+T- (2.10-fold) and S+T+F- (2.61-fold) stages) and higher accumulation of osmolytes (shoot proline for F-stage (5.82-fold) and S+T+F- (2.31-fold) stage), indicating better antioxidant capacitance and osmotic adjustment, respectively. In contrast, higher shoot accumulation of Na+ (14.25-fold) and consequent increase in Na+/K+ (14.56-fold), Na+/Mg+2 (13.09-fold) and Na+/Ca+2 (8.38-fold) ratio in shoot, were identified as major variables associated with S-stage salinity in Jaya. Higher root Na+ and their associated ratio were major deriving force for other stage specific and combined stage salinity in Jaya. In addition, CSR36 exhibited higher levels of Fe3+, Mn2+ and Co3+ and lower Cl- and SO42-, suggesting its potential to discriminate essential and non-essential nutrients, which might contribute to NaCl stress tolerance. Taken together, the findings provided the framework for stage-specific salinity responses in rice, which will facilitate crop-improvement programs for specific ecological niches, including coastal regions.

Identification and profiling of arsenic stress-induced microRNAs in Brassica juncea.

MicroRNAs (miRNAs) constitute a novel mechanism of gene regulation affecting plant development, growth, and stress response. To study the role of miRNAs in arsenic (As) stress, microarray profiling of miRNAs was performed in Brassica juncea using a custom Phalanx Plant OneArray containing 381 unique miRNA probes representing 618 miRNAs from 22 plant species. miRNA microarray hybridization of roots exposed to As for 1h and 4h revealed that a total of 69 miRNAs belonging to 18 plant miRNA families had significantly altered expression. The As-responsive miRNAs also exhibited a time- and organ-dependent change in their expression. Putative target prediction for the miRNAs suggested that they regulate various developmental processes (e.g. miR156, miR169, and miR172), sulphur uptake, transport, and assimilation (miR395, miR838, and miR854), and hormonal biosynthesis and/or function (e.g. miR319, miR167, miR164, and miR159). Notable changes were observed in the level of auxins [indole-3-acetic acid (IAA), indole-3- butyric acid, and naphthalene acetic acid], jasmonates [jasmonic acid (JA) and methyl jasmonate], and abscisic acid. The exogenous supply of JA and IAA improved growth of plants under As stress and altered expression of miR167, miR319, and miR854, suggesting interplay of hormones and miRNAs in the regulation of As response. In conclusion, the present work demonstrates the role of miRNAs and associated mechanisms in the plant's response towards As stress.

Comprehensive mechanisms of heavy metal toxicity in plants, detoxification, and remediation.

Natural and anthropogenic causes are continually growing sources of metals in the ecosystem; hence, heavy metal (HM) accumulation has become a primary environmental concern. HM contamination poses a serious threat to plants. A major focus of global research has been to develop cost-effective and proficient phytoremediation technologies to rehabilitate HM-contaminated soil. In this regard, there is a need for insights into the mechanisms associated with the accumulation and tolerance of HMs in plants. It has been recently suggested that plant root architecture has a critical role in the processes that determine sensitivity or tolerance to HMs stress. Several plant species, including those from aquatic habitats, are considered good hyperaccumulators for HM cleanup. Several transporters, such as the ABC transporter family, NRAMP, HMA, and metal tolerance proteins, are involved in the metal acquisition mechanisms. Omics tools have shown that HM stress regulates several genes, stress metabolites or small molecules, microRNAs, and phytohormones to promote tolerance to HM stress and for efficient regulation of metabolic pathways for survival. This review presents a mechanistic view of HM uptake, translocation, and detoxification. Sustainable plant-based solutions may provide essential and economical means of mitigating HM toxicity.

Sesuvium portulacastrum (L.) L.: a potential halophyte for the degradation of toxic textile dye, Green HE4B.

Sesuvium portulacastrum is a common halophyte growing well in adverse surroundings and is exploited mainly for the environmental protection including phytoremediation, desalination and stabilization of contaminated soil. In the present investigation, attempts have been made on the decolorization of a toxic textile dye Green HE4B (GHE4B) using in vitro grown Sesuvium plantlets. The plantlets exhibited significant (70%) decolorization of GHE4B (50 mg l(-1)) that sustain 200 mM sodium chloride (NaCl) within 5 days of incubation. The enzymatic analysis performed on the root and shoot tissues of the in vitro plantlets subjected to GHE4B decolorization in the presence of 200 mM NaCl showed a noteworthy induction of tyrosinase, lignin peroxidase and NADH-DCIP reductase activities, indicating the involvement of these enzymes in the metabolism of the dye GHE4B. The UV-visible spectrophotometer, HPLC and Fourier Transform Infrared Spectroscopy (FTIR) analyses of the samples before and after decolorization of the dye confirmed the efficient phytotransformation of GHE4B in the presence of 200 mM NaCl. Gas Chromatography-Mass Spectroscopy (GC-MS) analysis of the products revealed the formation of three metabolites such as p -amino benzene, p -amino toluene and 1, 2, 7-amino naphthalene after phytotransformation of GHE4B. Based on the FTIR and GC-MS results, the possible pathway for the biodegradation of GHE4B in the presence of 200 mM NaCl has been proposed. The phytotoxicity experiments confirmed the non-toxicity of the degraded products. The present study demonstrates for the first time the potential of Sesuvium for the efficient degradation of textile dyes and its efficacy on saline soils contaminated with toxic compounds.