Nanoparticle-mediated amelioration of drought stress in plants: a systematic review.

Drought stress remains one of the most detrimental environmental constraints that hampers plant growth and development resulting in reduced yield and leading to economic losses. Studies have highlighted the beneficial role of carbon-based nanomaterials (NMs) such as multiwalled carbon nanotubes (MWNTs), single-walled carbon nanotubes (SWNTs), graphene, fullerene, and metal-based nanoparticles (NPs) (Ag, Au, Cu, Fe2O3, TiO2, and ZnO) in plants under unfavorable conditions such as drought. NPs help plants cope with drought by improving plant growth indices and enhancing biomass. It improves water and nutrient uptake and utilization. It helps retain water by altering the cell walls and regulating stomatal closure. The photosynthetic parameters in NP-treated plants reportedly improved with the increase in pigment content and rate of photosynthesis. Due to NP exposure, the activation of enzymatic and nonenzymatic antioxidants has reportedly improved. These antioxidants play a significant role in the defense system against stress. Studies have reported the accumulation of osmolytes and secondary metabolites. Osmolytes scavenge reactive oxygen species, which can cause oxidative stress in plants. Secondary metabolites are involved in the water retention process, thus improving plant coping strategies with stress. The deleterious effects of drought stress are alleviated by reducing malondialdehyde resulting from lipid peroxidation. Reactive oxygen species accumulation is also controlled with NP treatment. Furthermore, NPs have been reported to regulate the expression of drought-responsive genes and the biosynthesis of phytohormones such as abscisic acid, auxin, gibberellin, and cytokinin, which help plants defend against drought stress. This study reviewed 72 journal articles from 192 Google Scholar, ScienceDirect, and PubMed papers. In this review, we have discussed the impact of NP treatment on morphological, physio-biochemical, and molecular responses in monocot and dicot plants under drought conditions with an emphasis on NP uptake, transportation, and localization.

Physiological and biochemical traits positively modulate tissue-specific withanolides and untargeted metabolites in Withania somnifera (L.) dunal under salinity stress.

Withania somnifera (L.) Dunal (Ashwagandha) has been used in herbal medicines worldwide and in the Indian traditional medicinal system for 3000 years. It is a member of the Solanaceae family distributed across Asia, Africa, Australia, and Europe. Its bioactive secondary metabolite (withanolide) biosynthesis is sensitive to salinity stress, though the mechanism remains unexplored. Therefore, we investigated the effect of Sodium chloride (NaCl) on growth, photosynthesis, biochemical traits, tissue-specific withanolide, and untargeted metabolites in W. somnifera. Ashwagandha plants were raised in pots containing soil mixture and treated with different NaCl concentrations (0 as control, 10, 30, and 50 mM) for one month inside the greenhouse. NaCl stress significantly enhanced withaferin A (WFA) (3.79 mg/g), withanolide A (WA) (0.51 mg/g), and withanone (WN) (0.022 mg/g) at 50 mM NaCl groups in the shoot. Similarly, in the root, a significant increase in WFA (0.19 mg/g) and WN (0.0016 mg/g) were observed at 10 mM, WA (0.059 mg/g) at 30 mM, and withanolide B (WB) (0.013 mg/g) at 50 mM NaCl groups compared to control. LC-MS-based untargeted metabolite profiling revealed 37 differentially accumulated metabolites in all groups. Maximum abundance of glycyl-hydroxyproline (8X) followed by tyrosyl-valine (2X) and 3-hydroxy-beta-ionone (2X) were recorded at 50 mM NaCl groups compared to the control. This study showed for the first time that low NaCl stress enhances the biosynthesis of tissue-specific withanolides through physio-biochemical and metabolites adjustment. Overall, we demonstrated a multifaceted approach for cultivating medicinal crops in salt-affected areas with enhanced bioactive metabolites for healthcare and pharmaceutical industries.

Differential Gene Expression and Withanolides Biosynthesis During in vitro and ex vitro Growth of Withania somnifera (L.) Dunal.

Ashwagandha (Withania somnifera L. Dunal) is a medicinally important plant with withanolides as its major bioactive compounds, abundant in the roots and leaves. We examined the influence of plant growth regulators (PGRs) on direct organogenesis, adventitious root development, withanolide biosynthetic pathway gene expression, withanolide contents, and metabolites during vegetative and reproductive growth phases under in vitro and ex vitro conditions. The highest shooting responses were observed with 6-benzylaminopurine (BAP) (2.0 mg L-1) + Kinetin (KIN) (1.5 mg L-1) supplementation. Furthermore, BAP (2.0 mg L-1) + KIN (1.5 mg L-1) + gibberellic acid (GA3) (0.5 mg L-1) exhibited better elongation responses with in vitro flowering. Half-strength MS medium with indole-3-butyric acid (IBA) (1.5 mg L-1) exhibited the highest rooting responses and IBA (1.0 mg L-1) with highest fruits, and overall biomass. Higher contents of withaferin A (WFA) [∼8.2 mg g-1 dry weight (DW)] were detected in the reproductive phase, whereas substantially lower WFA contents (∼1.10 mg g-1 DW) were detected in the vegetative phase. Cycloartenol synthase (CAS) (P = 0.0025), sterol methyltransferase (SMT) (P = 0.0059), and 1-deoxy-D-xylulose-5-phosphate reductase (DXR) (P = 0.0375) genes resulted in a significant fold change in expression during the reproductive phase. The liquid chromatography-mass spectrometry (LC-MS) analysis revealed metabolites that were common (177) and distinct in reproductive (218) and vegetative (167) phases. Adventitious roots cultured using varying concentrations of indole-3-acetic acid (IAA) (0.5 mg L-1) + IBA (1.0 mg L-1) + GA3 (0.2 mg L-1) exhibited the highest biomass, and IAA (0.5 mg L-1) + IBA (1.0 mg L-1) exhibited the highest withanolides content. Overall, our findings demonstrate the peculiarity of withanolide biosynthesis during distinct growth phases, which is relevant for the large-scale production of withanolides.

He-Ne laser accelerates seed germination by modulating growth hormones and reprogramming metabolism in brinjal.

A plant's ability to maximize seed germination, growth, and photosynthetic productivity depends on its aptitude to sense, evaluate, and respond to the quality, quantity, and direction of the light. Among diverse colors of light possessing different wavelengths and red light shown to have a high impact on the photosynthetic and growth responses of the plants. The use of artificial light sources where the quality, intensity, and duration of exposure can be controlled would be an efficient method to increase the efficiency of the crop plants. The coherent, collimated, and monochromatic properties of laser light sources enabled as biostimulator compared to the normal light. The present study was attempted to use the potential role of the He-Ne laser as a bio-stimulator device to improve the germination and growth of brinjal and to investigate the possible interactions of plant and laser photons. A substantial enhancement was observed in germination index, germination time and seed vigor index of laser-irradiated than control groups. The enhanced germination rate was correlated with higher GA content and its biosynthetic genes whereas decreased ABA content and its catabolic genes and GA/ABA ratio were noted in laser-irradiated groups during seed germination than control groups. Further the expression of phytochrome gene transcripts, PhyA and PhyB1 were upregulated in laser-irradiated seedlings which correlate with enhanced seed germination than control. Elevated levels of primary metabolites were noted in the early stages of germination whereas modulation of secondary metabolites was observed in later growth. Consequently, significantly increased photosynthetic rate, stomatal conductance, and transpiration rate was perceived in laser-irradiated seedlings compare with control. The current study showed hormone and phytochrome-mediated mechanisms of seed germination in laser-irradiated groups along with the enhanced photosynthetic rate, primary and secondary metabolites.

Untargeted metabolomics and DNA barcoding for discrimination of Phyllanthus species.

ETHNOPHARMACOLOGICAL RELEVANCE: Phyllanthus species is extensively cultivated and used as edible fruits and herbal drugs. The Phyllanthus species are used extensively as ethnopharmacologically important materials in several countries, especially in Asia. Various Phyllanthus species are broadly used in the Ayurvedic system of medicine and deliberated as bitter, astringent, stomachic, diuretic, febrifuge, deobstruent, and antiseptic, and used for the treatment of digestive, genitourinary, respiratory, skin diseases, hepatopathy, jaundice, and renal calculus in India. Precise authentification of Phyllanthus species is a challenge due to morphological similarities and is important to avoid adulteration found in herbal drugs. Hence, there is a need to establish comprehensive methods for the identification of Phyllanthus species. AIM OF THE STUDY: In this study, we attempted to integrate untargeted metabolomics to identify species-specific metabolites with traditional phylogenetic analysis for identification and discrimination of nine Phyllanthus species. MATERIALS AND METHODS: Phyllanthus species such as P. acidus, P. amarus, P. debilis, P. emblica, P. virgatus, P. urinaria, P. lawii, P. myrtifolius, and P. reticulatus were collected. The liquid chromatography coupled mass spectrometry (LC-MS) was performed for untargeted metabolite profiling and MS/MS fragmentation analysis was performed for selected compounds. Further, the barcoding analysis was executed using plastid loci, rpoC1 to integrate with metabolite profiling data. RESULTS: The Principal Component Analysis (PCA) of leaf metabolites showed distinct clusters in different species. Through further analysis, we have also identified the qualitative and quantitative status of unique metabolites across the species, and the majority of the selected compounds were annotated. The metabolic fingerprinting and the hierarchical clustering indicated that though the P. deblis and P. virgatus are distantly related to each other, they are closely associated with their metabolic profiling. Similarly, P. myrtifolius and P. urinaria are closely related to each other with their metabolic fingerprints than the genetic alignment. Further, we performed barcoding with rpoC1 across nine Phyllanthus species (P. acidus, P. amarus, P. debilis, P. emblica, P. virgatus, P. urinaria, P. lawii, P. myrtifolius, and P. reticulatus). Sequence similarity search in the GenBank database showed rpoC1 barcode loci from nine Phyllanthus species showed significant identity (>97%) with the sequences of various Phyllanthus species. CONCLUSIONS: The bioactive metabolites and their abundance can be assigned to specific species thereby serving as a biological signature and indicators for potential therapeutic use. This study identified differential expression of 14 secondary metabolites from nine Phyllanthus species. Alkaloid compound zeatin was found specific to P. virgatus and delphinidin-3-O- ß -D-glucoside was not found in P. myrtifolius. Barcoding and phylogenetic analysis showed P. acidus is the most genetically distinct among the groups and the sequence pair between P.emblica-P.reticulatus and P.emblica-P.urinaria showed the least difference.

Red laser-mediated alterations in seed germination, growth, pigments and withanolide content of Ashwagandha [Withania somnifera (L.) Dunal].

Withania somnifera (L.) Dunal, generally well-known as Ashwagandha, is part of Indian traditional medicinal systems like Ayurveda, Siddha, and Unani for over 3000 years for treating an array of disorders. The chief bioactive component of this plant is the withanolides, a group of C28-steroidal lactone triterpenoids. These compounds are present in very low concentrations and hence cell culture methods have been used to enhance their production. Low-level laser irradiation has been reported to have elicited the seed germination, agronomical characters, biosynthesis of bioactive compounds in some plants. Therefore, the objective of the study was to investigate the effect of red (He-Ne) laser irradiation on seed germination, growth characters, pigment contents and withanolide content in W. somnifera. The seeds were inoculated onto two different combinations of Murashige and Skoog (MS) media and incubated for germination. The highest germination percentage was observed in ½ MS with pH 6.5 and GA3 presoaking followed by ½ MS with different pH. Four different doses of Helium-Neon (He-Ne) laser (10, 15, 20 and 25 J/cm2) were used to irradiate the seeds at 632.8 nm and germinated in vitro on ½ MS with pH 6.5. The maximum germination percentage, 63.88% was noted from seeds irradiated with 25 J/cm2 (P = 0.04). The highest total length of 13.33 cm was observed in the seedlings irradiated with 25 J/cm2 groups (P = 0.008). The highest total chlorophyll content of 329.5 µg/g fresh weight (FW) was observed for seedlings irradiated with 15 J/cm2 (P = 0.02) and the highest carotenoid content of 49.6 µg/g FW was observed for 25 J/cm2 treated seedlings. Further, primary root length was measured and found to be highest (11.14 cm) in seedlings irradiated with 10 J/cm2 and the highest number of lateral roots were observed for 15 and 25 J/cm2 groups. The significant amount of Withanolide A (WA) 0.52 µg/g dry weight (DW) and 0.60 µg/g DW was noted in 15 (P = 0.01) and 20 J/cm2 (P = 0.002) groups, respectively than control. The present investigation thus reveals the positive impact of red laser on the germination of seeds, growth characters and withanolide contents under in vitro environment.

ROS-dependent DNA damage and repair during germination of NaCl primed seeds.

Reactive oxygen species (ROS) generated during rehydration of seeds is a major source of cellular damage. Successful germination depends on maintaining the oxidative window and ability of the cells to repair the DNA damage accumulated during seed developmental process, maturational drying, and germination. We explored the role of DNA damage, repair, cell cycle progression and antioxidant machinery in germination of seeds of Solanum melongena L. primed with 0, 320, 640 and 1200 mM sodium chloride (NaCl). The expression of antioxidant genes such as ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase2 (CAT2), and glutathione reductase (GR) was upregulated to maintain the oxidative window required for germination in seeds treated with 320 mM NaCl. ROS generated upon treatment with 320 mM NaCl resulted in minimal DNA damage and activated non-homologous end joining (NHEJ) and mismatch repair (MMR) pathway genes such as KU70 and mutS homolog 2 (MSH2) respectively. Treatment with higher concentrations of NaCl resulted in increased DNA damage despite lower ROS, without evoking DNA repair mechanisms. Uncontrolled rehydration resulted in higher levels of ROS and DNA damage, but activation of homologous recombination (HR) pathway gene, Nijmegen breakage syndrome 1 (NBS1), and genes involved in repairing oxidized guanine, such as oxoguanine DNA glycosylase (OGG1) and proliferating cell nuclear antigen (PCNA). In summary, controlled rehydration with 320 mM NaCl decreased the DNA damage, reactivated the antioxidant and DNA repair machinery, and cell cycle progression, thereby enhancing the seed germination.

In vitro culture responses, callus growth and organogenetic potential of brinjal (Solanum melongena L.) to He-Ne laser irradiation.

The present investigation was designed to analyze the influence of Helium-Neon (He-Ne 632.8nm) laser irradiation on defense enzymes, proline content and in vitro responses of callus induction, shoot initiation and on plantlet regeneration potential of brinjal. The seeds of Mattu Gulla (Solanum melongena L.) were irradiated with 20, 25 and 30J/cm2 of He-Ne laser followed by surface sterilization and sprouted on Murashige and Skoog medium without plant growth regulators. The activity of defense enzymes, proline content and the organogenetic potential of hypocotyl, leaf and shoot tip explants were determined from thirty day old seedlings. During seed germination, most of the seedlings showed normal two cotyledons whereas small number of seedlings showed tricotyledonous at 20J/cm2 treatment and no other morphological abnormalities were observed during further growth and development. There was no substantial variation was noted in both ß-1,3-glucanase and chitinase activity as well as proline content which proves the He-Ne laser irradiation does not causes any stresses for the plant. The in vitro culture of hypocotyl, leaf and shoot tip explants from laser irradiated seedlings showed differential responses as compared to un-irradiated control. The laser induced enhancement of callus induction, growth rate of callus tissues and shoot tip, percentage of responses of shoot and root initiation, days to shoot and root initiation, shoots formed per callus, number of roots per shoots, length of roots and nuclear DNA content of in vitro raised plants were evaluated. Among the tested laser doses (20, 25 and 30J/cm2), 25J/cm2 showed significant biostimulatory effect over un-irradiated control seedlings. The present observations reveal and endorsed our earlier reports with substantial enhancement of in vitro and ex vitro by He-Ne laser irradiation.

Responses of He-Ne laser irradiation on agronomical characters and chlorogenic acid content of brinjal (Solanum melongena L.) var. Mattu Gulla.

Exposure to laser irradiation on seeds brings about the changes in agronomical characteristics of the plants. Solanum melongena L. var. Mattu Gulla, a variety of brinjal is of high economic value due to its unique colour and flavour. The aim of the study was to understand the influence of Helium-Neon (He-Ne) laser irradiation on agronomical characters of Solanum melongena L. var. Mattu Gulla in the field conditions. Various growth characteristics including seed germination percentage, survival rate, plant height, number of branches, and flowers and fruits were estimated during different developmental stages of the brinjal. In addition, the chlorogenic acid content of fruits obtained from the laser irradiated seeds were quantified using reversed-phase high-performance liquid chromatography (RP- HPLC). The plants from the seeds irradiated with different doses (20, 25 and 30J/cm2) of He-Ne laser showed significant enhancement on the growth characteristics when compared to the non-irradiated control groups. He-Ne laser irradiation also improved the yield characteristics of the plants significantly in in vivo conditions in comparison with control group. 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed using methanolic extract of matured fruit of Mattu Gulla on HepG2 and fibroblast cell lines. The IC50 values of fruit extract from laser irradiated groups were found to be similar to non-irradiated control groups. Chlorogenic acid content was found to be higher in 20J/cm2 and lower in 30J/cm2 treated fruit tissue. The current study thus elucidates the role of He-Ne laser as a biostimulator on brinjal var. Mattu Gulla not only in the in vitro conditions but also in the in vivo field conditions.

Radiation and chemical mutagen induced somaclonal variations through in vitro organogenesis of cotton (Gossypium hirsutum L.).

PURPOSE: The purpose of the investigation was to induce somaclonal variations by gamma rays (GR), ethylmethane sulphonate (EMS) and sodium azide (SA) during in vitro organogenesis of cotton. MATERIALS AND METHODS: The shoot tip explants were irradiated with 5-50 Gray (Gy) GR (Cobalt 60), 0.5-5.0 mM EMS and SA separately, and inoculated on Murashige and Skoog (MS) medium fortified with plant growth regulator (PGR) for organogenesis. The plantlets with well-developed root systems were acclimatized and transferred into the experimental field to screen the somaclonal variations during growth and development. RESULTS: The number of somaclonal variations was observed in growth of irradiated/treated shoot tips, multiplication, plantlet regeneration and growth in vitro and ex vitro. The lower doses/concentrations of mutagenic treatments showed significant enhancement in selected agronomical characters and they showed decreased trends with increasing doses/concentrations of mutagenic agents. CONCLUSIONS: The results of the present study revealed the influence of lower doses/concentrations of mutagenic treatments on in vitro and ex vitro growth of cotton plantlets and their significant improvement in agronomical characters which needs further imperative stability analysis. The present observations showed the platform to use lower doses/concentrations of mutagenic agents to induce variability for enhanced agronomical characters, resistant and tolerant cotton varieties.

Variations in seed protein content of cotton (Gossypium hirsutum L.) mutant lines by in vivo and in vitro mutagenesis.

The present work describes the influence of gamma irradiation (GR), ethyl methane sulphonate (EMS) and sodium azide (SA) treatment on yield and protein content of selected mutant lines of cotton. Seeds of MCU 5 and MCU 11 were exposed to gamma rays (GR), ethyl methane sulphonate (EMS) and sodium azide (SA). Lower dose of gamma irradiation (100-500 Gy), 10-50 mM EMS and SA at lower concentration effectively influences in improving the yield and protein content. Significant increase in yield (258.9 g plant(-1)) and protein content (18.63 mg g(-1) d. wt.) as compared to parental lines was noted in M2 generations. During the subsequent field trials, number of mutant lines varied morphologically in terms of yield as well as biochemical characters such as protein. The selected mutant lines were bred true to their characters in M3 and M4 generations. The significant increase in protein content and profiles of the mutant lines with range of 10.21-18.63 mg g(-1). The SDS-PAGE analysis of mutant lines revealed 9 distinct bands of different intensities with range of 26-81 kDa. The difference in intensity of bands was more (41, 50 and 58 kDa) in the mutant lines obtained from in vitro mutation than in vivo mutation. Significance of such stimulation in protein content correlated with yielding ability of the mutant lines of cotton in terms of seed weight per plant. The results confirm that in cotton it is possible to enhance the both yield and biochemical characters by in vivo and in vitro mutagenic treatments.

Influence of helium-neon laser irradiation on seed germination in vitro and physico-biochemical characters in seedlings of brinjal (Solanum melongena L.) var. Mattu Gulla.

In the present study, the seeds of brinjal (Solanum melongena L.) var. Mattu Gulla were irradiated with single exposure of He-Ne laser at different doses of 5-40 J cm(-2) and germinated aseptically. Thirty day old seedlings were harvested and the germination, growth, physiological and biochemical parameters were estimated and compared with un-irradiated control seedlings. A significant enhancement in growth characters were noted with respect to length, fresh and dry weight of shoots and roots. In addition, chlorophyll (a and b), carotenoid content, anthocyanin and amylases (α and ß) activities were found to be altered. Significant alterations in percentage of seed germination (P < 0.001) and time to 50% germination (P < 0.001) were observed in the irradiated seeds compared with the un-irradiated controls. In conclusion, the results of the present study demonstrated that low dose (5-30 J cm(-2) ) of He-Ne laser irradiation enhanced the germination process and altered growth, by positively influencing physiological and biochemical parameters of the brinjal seedlings compared with un-irradiated control under in vitro conditions.