Previously, we showed that altered sulfite homeostasis led to higher water loss in Sulfite oxidase RNA interference (SO Ri) plants than in Arabidopsis wild-type (WT) after sulfite infiltration into rosette leaves. In contrast, SO overexpression (OE) and adenosine-5'-phosphosulfate reductase (apr2) KO resulted in lower water loss than in WT. Accordingly, sulfite homeostasis and drought tolerance under prolonged drought in Arabidopsis thaliana and tomato (Rheinlands Ruhm) were investigated. SO Ri mutants displayed the most severe wilting and water loss, accompanied by sulfite accumulation due to reduced SO expression. In contrast, SO OE, apr2 KO, apr2 KO/SO OE, and gene-edited lines, including SiR OEC2+SO OEC2 and SiR OEC4/SO OE maintained higher relative water content (RWC) by enhancing sulfite oxidation and reduction. Elevated sulfite in SO Ri mutants acted as an antagonist to abscisic acid (ABA), as despite accumulating higher ABA than all other genotypes, SO Ri plants displayed the lowest RWC, consistent with sulfite suppressing ABA signal transduction through impaired ABA perception (PYL5) and enhanced ABA negative feedback (HAI2). SO and SiR overexpression also increased hydrogen sulfide and cysteine levels, contributing to drought resilience. Tomato lines also reflected these patterns in SO OE, SiR OE, and SiR OE/SO OE, showing reduced sulfite and improved RWC compared to WT. Overall, coordinated regulation of SO, SiR, and APR2 maintains sulfite homeostasis, mitigating drought-induced damage and enhancing water retention across species by directly limiting sulfite accumulation and relieving sulfite-driven antagonism of ABA signal transduction.

The effects of postharvest storage delays of 1 and 2 hours on the nutritional quality of halophytic plants irrigated with 100 and 150 mM NaCl solutions were assessed. The study compared the new Sarcocornia fruticosa ecotypes Shikmona, Megadim, and Ruhama with the commonly cultivated VM and Arthrocaulon macrostachyum (AM). All new ecotypes outperformed the VM ecotype in terms of nutritional composition and yield. Except for Shikmona, the biomass of all ecotypes increased with elevated salinity; however, storage delays reduced water content, with a greater reduction under lower salinity. Storage delays in Sarcocornia significantly enhanced total polyphenols, flavonoids, carotenoids, anthocyanins, and radical-scavenging activity compared with levels in the plant contents immediately after harvesting.,In contrast, AM showed declines in antioxidants, except for anthocyanins and carotenoids, after 1- and 2-hour delays. Both storage delays increased total soluble sugars, electrical conductivity, and malondialdehyde in AM and the Sarcocornia ecotypes. Further carotenoid enhancement in AM was observed in the 2-hour storage-delay treatment, followed by 21 days of storage, compared with the control stored immediately for 21 days.,Across Sarcocornia ecotypes, storage delay is associated with increased levels of polyphenols, flavonoids, and carotenoids, as well as enhanced radical-scavenging activity. In contrast, AM showed decreased total flavonoids, polyphenols, and radical scavenging activity after a 2-hour storage delay, followed by 21 days of cold room storage, compared to 21 days of storage without a delay. Yet, its antioxidant content remained higher than that of the Sarcocornia ecotypes in both the non-delayed control and the 2-hour storage-delay treatments.

The aim of the present study is functional characterization of a native plant defensin gene (AhDef1) from Arachis hypogaea (peanut). Further its potential has been evaluated to enhance resistance against Aspergillus flavus infection and reduce aflatoxin accumulation through transgenic intervention. Transgenic peanut lines overexpressing the AhDef1 gene exhibited significantly improved resistance to A. flavus colonization and a marked reduction in aflatoxin B1 content compared to wild-type (WT) plants. Quantitative real-time PCR confirmed transgene expression, and aflatoxin accumulation was analyzed by a spectrophotometer which revealed a reduction in aflatoxin levels in the transgenic seeds. Alongside its direct antifungal activity, AhDef1 overexpression also triggered the upregulation of genes which are involved in the biosynthesis of secondary metabolites such as resveratrol, ferulic acid and butenedioic acid, myoinositol, octadecanoic acid, suggesting an amplified biochemical defense response. Multivariate analysis further suggested that accumulation of these defense-related metabolites was positively correlated with transgenic lines challenged by A. flavus. In conclusion, the AhDef1 gene functionally validated in this study emerges as a promising candidate for engineering fungal disease resistance and aflatoxin mitigation in peanut and potentially other susceptible crops.

Halophyte bio-saline agriculture can supplement conventional farm methods in salinized soils and salty water. The current study compares the yield and nutritional value of new Sarcocornia fruticosa ecotypes (Shikmona, Megadim, Naaman, and Ruhama) to those of the current ecotype (VM). Additionally, Arthrocaulon macrostachyum, phenotypically similar to Sarcocornia, was compared to Sarcocornia ecotypes, and the effects of the harvesting regime and irrigation water salinity on yield and nutritional value were studied. At both salinity levels (50 and 150 mM NaCl), 30-day harvesting intervals over a 210-day growth period increased plant yield compared to a 21-day regime. It also tended to improve electrical conductivity (EC) and total soluble sugars (TSS), lower malondialdehyde levels (a marker of toxic stress), and enhance radical inhibition activity in most ecotypes. Compared to VM, the Sarcocornia ecotypes Ruh and Naa exhibited much higher biomass with similar radical inhibition activity but lower total protein content. Higher salinity improved fresh biomass, shoot diameter, relative water content, chlorophyll level, TSS, and EC and tended to increase anthocyanin and carotenoid levels. In contrast, lower salinity tended to increase total flavonoids, polyphenols, and radical inhibition activity. In the 30-day harvest regime, A. macrostachyum exhibited the highest and second-highest yields at high and low salinity, respectively; the highest shoot diameter, total flavonoids, and radical inhibition activity; and one of the lowest malondialdehyde levels. The current study highlights the importance of optimizing harvest frequency and the advantages of employing A. macrostachyum and the Sarcocornia ecotypes Ruhama, Naaman, and Megadim with a 30-day harvesting regime under higher-salinity conditions.

This study focused on enzyme-assisted extraction of polysaccharides from four selected tropical green seaweeds (Caulerpa scalpelliformis, Ulva fasciata, Ulva lactuca, and Acrosiphonia orientalis). The polysaccharides were physicochemically characterized by using advanced analytical tools and also evaluated for their scavenging and anti-proliferative activities. Enzyme-assisted extraction yielded a higher polysaccharide content compared with traditional techniques. The extracted crude and purified polysaccharides were rich in sugars, including galactose and mannose. Functional group analysis based on Fourier-transform infrared spectroscopy confirmed the presence of characteristic polysaccharide groups, such as hydroxyl, carboxyl, and sulfate. The extracted polysaccharides were amorphous in nature with a fibrous and porous morphology, showing uneven aggregates. Different biological tests, including the ferric reducing antioxidant power and phosphomolybdate assays, revealed significant antioxidant activity. Furthermore, the anti-proliferative studies performed on two cancer cell lines (Huh-7 and HeLa) showed different degrees of inhibition, with certain purified fractions showing higher efficacy. Overall, the results indicate that these extracted polysaccharides have potential applications in nutraceutical, pharmaceutical, and therapeutic products, particularly as antioxidants and anti-cancer agents.

This study aims to elucidate the regulatory role of the Salicornia brachiata aquaporin gene (SbPIP2) promoter, in response to abiotic stress in plants. Through computational analysis, we identified an array of cis-regulatory elements within the 1800 bp SbPIP2 promoter region. To functionally characterize this promoter, we constructed five sequential deletions and two specific deletions targeting the ABRE and AS-1 elements, and fused them to a GUS reporter gene. Quantitative GUS assays revealed a 5.7-fold increase in expression under abiotic stress conditions for the full-length promoter. Compared to the CaMV 35S promoter, the SbPIP2 promoter showed half the expression levels under unstressed conditions, but displayed a three-fold increase under abiotic stress. Deletion of ABRE and AS-1 elements confirmed their roles in elevated promoter activity and stress responsiveness, respectively. Additionally, quantitative MUG assays highlighted the presence of tissue-specific repressor sites between positions − 1027 to − 707 in the stem and root. Our findings provide critical insights into the SbPIP2 promoter's architecture and function, and identify key motifs for targeted manipulation to enhance abiotic stress tolerance in crops. This work contributes substantially to our understanding of molecular mechanisms in plant stress responses, setting the stage for the development of more resilient agricultural systems in the context of climate change.

Abiotic stress-induced reactive carbonyl species (RCS) accumulation in plants stimulates oxidative stress by DNA adduct formation, protein carbonylation, and antioxidant pool depletion, triggering senescence or programmed cell death. RCS accumulation under abiotic stress has rarely been studied in halophytic plants that are adapted to highly saline environments. In the current study, exposure to UV-C irradiation resulted in a higher RCS accumulation in the halophytic Sarcocornia fruticosa ecotypes VM and EL than in Salicornia brachiata (SB) and Arthrocnemum macrostachyum (AM). Accordingly, SB and AM recovered better, whereas VM and EL showed significant damage 14 days after UV-C application. Reduced aldehyde oxidase (AO) activity, recently shown to detoxify carbonyl aldehydes in Arabidopsis plants, is likely responsible for the significantly higher RCS accumulation and damage in the VM and EL plants. As evidence for this, the VM plants exposed to exogenously applied 3 mM of malondialdehyde or 3 mM of benzaldehyde exhibited decreased AO activity, which resulted in the accumulation of endogenous RCS and severe damage, including mortality. In contrast, the AM plants were able to detoxify RCS by AO activity enhancement, exhibiting recovery after 25 days. These results highlight the role of RCS accumulation in VM and EL plant tissue damage, while improved AO activity, which resulted in improved RCS detoxification in SB and AM, promoted better recovery.

Among the three active aldehyde oxidases in Arabidopsis thaliana leaves (AAO1-3), AAO3, which catalyzes the oxidation of abscisic-aldehyde to abscisic-acid, was shown recently to function as a reactive aldehyde detoxifier. Notably, aao2KO mutants exhibited less senescence symptoms and lower aldehyde accumulation, such as acrolein, benzaldehyde, and 4-hydroxyl-2-nonenal (HNE) than in wild-type leaves exposed to UV-C or Rose-Bengal. The effect of AAO2 expression absence on aldehyde detoxification by AAO3 and/or AAO1 was studied by comparing the response of wild-type plants to the response of single-functioning aao1 mutant (aao1S), aao2KO mutants, and single-functioning aao3 mutants (aao3Ss). Notably, aao3Ss exhibited similar aldehyde accumulation and chlorophyll content to aao2KO treated with UV-C or Rose-Bengal. In contrast, wild-type and aao1S exhibited higher aldehyde accumulation that resulted in lower remaining chlorophyll than in aao2KO leaves, indicating that the absence of active AAO2 enhanced AAO3 detoxification activity in aao2KO mutants. In support of this notion, employing abscisic-aldehyde as a specific substrate marker for AAO3 activity revealed enhanced AAO3 activity in aao2KO and aao3Ss leaves compared to wild-type treated with UV-C or Rose-Bengal. The similar abscisic-acid level accumulated in leaves of unstressed or stressed genotypes indicates that aldehyde detoxification by AAO3 is the cause for better stress resistance in aao2KO mutants. Employing the sulfuration process (known to activate aldehyde oxidases) in wild-type, aao2KO, and molybdenum-cofactor sulfurase (aba3-1) mutant plants revealed that the active AAO2 in WT employs sulfuration processes essential for AAO3 activity level, resulting in the lower AAO3 activity in WT than AAO3 activity in aao2KO.

Understanding the mechanisms behind plant resilience to abiotic stresses is essential for enhancing crop yield and sustainability. This study integrates findings from a comprehensive investigation into the function of the SbPIP2 gene, which encodes an aquaporin protein, in improving the abiotic stress tolerance of transgenic plants. Our integrated approach revealed that transgenic plants overexpressing SbPIP2 significantly reduce reactive oxygen species (ROS) accumulation and exhibit enhanced physiological attributes, including higher seed germination rates, improved growth, early flowering, and better seed setting under stress conditions. Notably, these plants also showed a quicker recovery and completion of their lifecycle post-stress treatment. The transcriptomic analysis provided a deeper understanding of the genetic modifications contributing to stress resilience, highlighting the involvement of genes associated with oxidative stress response, calcium and sugar signaling pathways, stomatal regulation, phytohormone biosynthesis, and flower development. Additionally, the study underscores the central role of abscisic acid (ABA) in mediating stress responses through hormonal regulation, with transgenic plants displaying increased ABA levels due to the upregulation of biosynthesis genes and downregulation of catabolism genes. This hormonal adjustment is critical for stomatal closure, reducing water loss, and enhancing tolerance to abiotic stresses. Our findings elucidate the complex genetic and molecular pathways that underpin abiotic stress tolerance in plants, offering valuable insights for future research aimed at improving crop resilience through genetic engineering, thereby addressing the challenges of climate change and environmental stressors.### Competing Interest StatementThe authors have declared no competing interest.

The present study aims to explore the potential of a plasma-membrane localized PIP2-type aquaporin protein sourced from the halophyte Salicornia brachiata to alleviate salinity and water deficit stress tolerance in a model plant through transgenic intervention. Transgenic plants overexpressing SbPIP2 gene showed improved physio-biochemical parameters like increased osmolytes (proline, total sugar, and amino acids), antioxidants (polyphenols), pigments and membrane stability under salinity and drought stresses compared to control plants [wild type (WT) and vector control (VC) plants]. Multivariate statistical analysis showed that, under water and salinity stresses, osmolytes, antioxidants and pigments were correlated with SbPIP2-overexpressing (SbPIP2-OE) plants treated with salinity and water deficit stress, suggesting their involvement in stress tolerance. As aquaporins are also involved in CO2 transport, SbPIP2-OE plants showed enhanced photosynthesis performance than wild type upon salinity and drought stresses. Photosynthetic gas exchange (net CO2 assimilation rate, PSII efficiency, ETR, and non-photochemical quenching) were significantly higher in SbPIP2-OE plants compared to control plants (wild type and vector control plants) under both unstressed and stressed conditions. The higher quantum yield for reduction of end electron acceptors at the PSI acceptor side [Phi(()(R0)())] in SbPIP2-OE plants compared to control plants under abiotic stresses indicates a continued PSI functioning, leading to retained electron transport rate, higher carbon assimilation, and less ROS-mediated injuries. In conclusion, the SbPIP2 gene functionally validated in the present study could be a potential candidate for engineering abiotic stress resilience in important crops.

Foods enriched with nutritional compounds and biological activities, especially antioxidants, are considered healthier for human and/or animal consumption. Seaweeds are rich sources of biologically active metabolites and are used as functional foods. In this study, proximate compositions, physicobiochemical characteristics and oil oxidative stability were analyzed for 15 abundant tropical seaweeds (four green—Acrosiphonia orientalis, Caulerpa scalpelliformis, Ulva fasciata, Ulva lactuca; six brown—Iyengaria stellata, Lobophora variegate, Padina boergesenii, Sargassum linearifolium, Spatoglossum asperum, Stoechospermum marginatum; and five red—Amphiroa anceps, Grateloupia indica, Halymenia porphyriformis, Scinaia carnosa, Solieria chordalis). All seaweeds were analyzed for the proximate composition, including moisture content, ash content, total sugar content, total proteins, total lipids, crude fiber, carotenoid content, total chlorophyll content, proline, iodine content, nitrogen-free extract, total phenolic content and total flavonoid content. Green seaweeds showed higher nutritional proximate composition, followed by brown and red seaweeds. Among the different seaweeds, Ulva, Caulerpa, Sargassum, Spatoglossum and Amphiroa showed high nutritional proximate composition compared to other seaweeds. High cation scavenging, free radical scavenging and total reducing activities were observed for Acrosiphonia, Caulerpa, Ulva, Sargassum, Spatoglossum and Iyengaria. It was also observed that 15 tropical seaweeds contained negligible amounts of antinutritional compounds, including tannic acid, phytic acid, saponins, alkaloids and terpenoids. Nutritionally, green and brown seaweeds provided higher sources of energy (150–300 calories per 100 g) compared to red seaweeds (80–165 calories per 100 g). Additionally, this study also confirmed that tropical seaweeds improved the oxidative stability of food oils and, therefore, might be recommended as natural antioxidant additives. The overall results confirm that tropical seaweeds are potential sources of nutrition and antioxidants and may be explored as functional food, dietary supplementation or animal feed. Additionally, they may also be explored as food supplements for fortifying food products, as food toppings or for garnishing and seasoning foods. However, a human or animal toxicity analysis is required before any conclusive recommendation for daily food or feed intake can be made.

Red macroalgae underpin many commercially important food, pharmaceutical and other important industries. To date, research into these species has generally focused on improving seaweed cultivation, developing new methods to extract useful compounds, or identify novel applications. Due to their economic importance, there is a requirement to develop a more complete understanding of the genome and metabolic pathways in these key seaweed species. This review describes progress in genomics, transcriptomics, protoplast isolation, and transformation approaches. It also explores the potential of genome editing using the CRISPR/Cas system to further our understanding of gene function related to different metabolic pathways and resolving unexplored aspects of macroalgal physiology traits linked to crop improvement. The application of functional genomics is essential to gain a complete understanding of both physiological and metabolomic processes, that will ultimately enhance the commercial resilience of macroalgae related industries that are subject to numerous pressures, including climate change. Although the use of genetic manipulation to alter growth characteristics or composition in seaweed will not readily apply to the macroalgae industry in the short term, it is likely to be critical for sustaining future commercial growth. The functional characterisation of macroalgal genes through the CRISPR/ Cas approach promises to open new avenues for translational research on utilising macroalgal resources for the sustainable development of these aquaculture systems.

The frequency and severity of extreme climatic conditions such as drought, salinity, cold, and heat are increasing due to climate change. Moreover, in the field, plants are affected by multiple abiotic stresses simultaneously or sequentially. Thus, it is imperative to compare the effects of stress combinations on crop plants relative to individual stresses. This study investigated the differential regulation of physio-biochemical and metabolomics parameters in peanut (Arachis hypogaea L.) under individual (salt, drought, cold, and heat) and combined stress treatments using multivariate correlation analysis. The results showed that combined heat, salt, and drought stress compounds the stress effect of individual stresses. Combined stresses that included heat had the highest electrolyte leakage and lowest relative water content. Lipid peroxidation and chlorophyll contents did not significantly change under combined stresses. Biochemical parameters, such as free amino acids, polyphenol, starch, and sugars, significantly changed under combined stresses compared to individual stresses. Free amino acids increased under combined stresses that included heat; starch, sugars, and polyphenols increased under combined stresses that included drought; proline concentration increased under combined stresses that included salt. Metabolomics data that were obtained under different individual and combined stresses can be used to identify molecular phenotypes that are involved in the acclimation response of plants under changing abiotic stress conditions. Peanut metabolomics identified 160 metabolites, including amino acids, sugars, sugar alcohols, organic acids, fatty acids, sugar acids, and other organic compounds. Pathway enrichment analysis revealed that abiotic stresses significantly affected amino acid, amino sugar, and sugar metabolism. The stress treatments affected the metabolites that were associated with the tricarboxylic acid (TCA) and urea cycles and associated amino acid biosynthesis pathway intermediates. Principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA), and heatmap analysis identified potential marker metabolites (pinitol, malic acid, and xylopyranose) that were associated with abiotic stress combinations, which could be used in breeding efforts to develop peanut cultivars that are resilient to climate change. The study will also facilitate researchers to explore different stress indicators to identify resistant cultivars for future crop improvement programs.

A potent cold and drought regulatory-protein encoding gene, SbCDR was cloned from an extreme halophyte Salicornia brachiata. In vitro localisation study, performed with SbCDR::RFP gene-construct revealed that SbCDR is a membrane protein. Overexpression of the SbCDR gene in tobacco plants confirmed tolerance against major environmental constraints such as salinity, drought and cold, as evidenced by improved chlorophyll contents, plant morphology, plant biomass, root length, shoot length and seed germination efficiency. Transgenic lines also exhibited high accumulation of proline, total sugar, reducing sugar, free amino acid and polyphenol, besides the low level of malondialdehyde (MDA) contents. SbCDR transgenic lines showed better relative water contents, membrane stability index and osmotic water potential. Furthermore, higher expression of ROS scavenging genes was observed in transgenic lines under stress. Moreover, microarray analysis revealed that several host genes were upregulated and downregulated under drought and salt stress conditions in SbCDR transgenic line compared with control (WT) plants. The results demonstrated that the overexpression of the halophytic SbCDR gene has intense effects on the abiotic stress tolerance of transgenic tobacco plants. However, the exact mode of action of SbCDR in multiple abiotic stress tolerance of plants is yet to be unveiled. It is believed that the precise role of SbCDR gene will provide additional information to comprehend the abiotic stress tolerance mechanism. Furthermore, it will appear as a promising candidate gene for improving stress tolerance in different crop plants for sustainable agriculture and crop productivity.

Metallothioneins are cysteine-rich proteins, which play key roles in metal detoxification, intracellular ion homeostasis maintenance, and protection against intracellular oxidative damage. This study reports the characterization of SbMT-2 cloned from Salicornia brachiata concerning physiology, molecular, and photosynthesis efficiency. Overexpression of SbMT-2 conferred enhanced tolerance to Zn stress in transgenic tobacco supported by increased photosynthesis efficiency and crop quality compared to wild-type. The growth of transgenic and WT plants was comparable in control conditions; transgenic plants showed better growth than WT plants under stress (20 mM ZnSO4 for 30 days). After 30 days of stress, transgenic plants completed their life cycle with early maturation, whereas the WT plants did not and matured very late. About 35 pods with a total weight of 3.5 g per plant were measured in transgenic compared to WT (about 19 pods with total weight 2.5 g). Further, gas exchange and fluorescence measurements established that the SbMT-2 gene improved the photosynthetic efficiency of the transgenic line compared to WT plants during stress conditions. In addition, SbMT-2 might be involved in the selective translocation of Zn2+ under long-term stress condition. Microarray analysis showed that the expression of many Zn transporters, Zn-binding proteins, and Zn-associated proteins encoding genes was upregulated 4-6 (log2) fold. However the expression of genes encoding other metal-binding proteins, metal metabolism-associated enzymes, and metal-inducible transcription factors were down-regulated. Furthermore, transcript expression analysis elucidated that overexpression of the SbMT-2 gene may regulate the expression pattern of metal transporter encoding genes under stress conditions. Thus, SbMT-2 is an important gene, which plays a positive role by detoxifying reactive oxygen species and maintaining photosynthesis efficiency under Zn stress conditions.

Soon after discovery, immense work has been carried out on biochemical characterization and functional validation of plant sodium–proton (Na+/H+) antiporters (NHXs). NHXs are integral membrane proteins localized at the various membranes of a plant cell, including endomembrane compartments and plasma membrane. Transgenic model and crop plants, overexpressing NHXs isolated from both glycophytes and halophytes, were developed and well-studied for their role in abiotic stress tolerance, especially in salt and drought stress. NHXs exchange Na+ and K+ with H+ ions by using proton motive force generated by plasma membrane H+ ATPase (P-H+ ATPase) and vacuolar H+ ATPase (V-H+ ATPase) coupled with H+ PPase, located at the plasma membrane and tonoplast, respectively. NHXs execute the inevitable process of pH and Na+/K+ ion homeostasis in plants during normal growth condition and also under abiotic stresses. Apart from this, NHXs are found to be involved in the regulation of cell physiology, osmotic adjustments, cell turgor maintenance, protein processing and trafficking, microtubule organization, and the development of roots, embryo, and flowers. Recently, T-DNA insertional mutants and gene knockout studies clearly show the role of NHXs in abiotic stress tolerance with characteristics like altered leaf growth and decrease in epidermal cell frequency, leaf surface area, root cell size in the transition zone, and stomatal functions. As a consequence, it can be concluded that NHXs antiporters play a crucial role in the cellular homeostasis of plants under abiotic stresses.

Water is a vital resource for plants to grow, thrive, and complete their life cycle. In recent years, drastic changes in the climate, especially drought frequency and severity, have increased, which reduces agricultural productivity worldwide. Aquaporins are membrane channels belonging to the major intrinsic protein superfamily, which play an essential role in cellular water and osmotic homeostasis of plants under both control and water deficit conditions. A genome-wide search reveals the vast availability of aquaporin isoforms, phylogenetic relationships, different families, conserved residues, chromosomal locations, and gene structure of aquaporins. Furthermore, aquaporins gating and subcellular trafficking are commonly controlled by phosphorylation, cytosolic pH, divalent cations, reactive oxygen species, and stoichiometry. Researchers have identified their involvement in regulating hydraulic conductance, root system architecture, modulation of abiotic stress-related genes, seed viability and germination, phloem loading, xylem water exit, photosynthetic parameters, and post-drought recovery. Remarkable effects following the change in aquaporin activity and/or gene expression have been observed on root water transport properties, nutrient acquisition, physiology, transpiration, stomatal aperture, gas exchange, and water use efficiency. The present review highlights the role of different aquaporin homologs under water-deficit stress condition in model and crop plants. Moreover, the opportunity and challenges encountered to explore aquaporins for engineering drought-tolerant crop plants are also discussed here.

There is an urgent need to develop quality crop with improved productivity and wider tolerance to the environmental (biotic and abiotic) stresses for addressing different issues including global water crisis, food security, and climate change effect on agriculture. Traditional lengthy procedures for crop improvement including classical breeding and random mutagenesis will not be able to fulfill growing crop demand in near future. Gene targeting technology is a powerful transformative procedure that permits accurate genetic modification in any genome which relies on a variety of molecular editors. Formation of directed DNA cleavage by ZFNs, TALENs, and CRISPR/Cas9, followed by restoration via the DNA repair system either by NHEJ (non-homologous end joining) or by HDR (homology directed recombination), provides a useful insight of gene function and trait modification. In this chapter, we have described the four available types of genome editing tools; meganucleases, ZFNs, TALENs, and CRISPR systems, and discussed their revolutionary applications in precision molecular breeding and functional genomics research of crops. Furthermore, specific challenges in the plant genome editing and prospects were also reviewed.

The world's population is increasing daily, with corresponding demands for sustainable food production, but about 800 million ha of land is affected by salt. Salinization is gradually increasing for several reasons, including scanty rainfall, poor irrigation practices, salt ingression and natural calamities. Salinity is considered a major abiotic stress that adversely affects the growth and productivity of crop plants. Commonly, crop plants are salt sensitive (glycophytes) and so cannot grow in the salt-affected areas. Some plants have natural ability to grow in the high saline areas and are known as halophytes. Halophytes require salt to complete their life cycle and are thus considered potential sources for salt-responsive genes and promoters. The salt-tolerance mechanism is a very complex process which is coordinated from stress perception to signal transduction, and thus provides stress endurance. Several potential salinity-stress responsive and tolerance genes have been isolated from halophytes, functionally characterized and explored for developing transgenic crop plants for sustainable agriculture in the salt-affected areas. About one-quarter of the entire Arabidopsis genome responds to salt stress, and so the search continues for promising stress-responsive genes that can modulate physiological traits and metabolic pathways without imposing yield penalties. This chapter focuses on the examination of halophytes for salt-responsive genes, their functional validation and further utilization to engineer crop plants.