Exogenous methyl jasmonate enhanced kenaf (Hibiscus cannabinus) tolerance against lead (Pb) toxicity by improving antioxidant capacity and osmoregulators.

In this study, the effects of exogenous methyl jasmonate (MeJA) on metal uptake and its ability to attenuate metal toxicity in kenaf plants under Pb stress were investigated. The experiment was conducted with five different MeJA concentrations (0, 40, 80, 160, and 320 µM) as a foilar application to kenaf plants exposed to 200 µM Pb stress. The results revealed that pretreatmen of MeJA significantly increased plant dry weight, plant height, and root architecture at all concentrations tested, with the most significant increase at 320 µM. Foliar application of MeJA at 160 µM and 320 µM increased the Pb concentrations in leaves and stems as well as the translocation factor (TF) from root to leaf. However, the bioaccumulation factor in the shoot initially decreased and then increased with increasing MeJA concentration. By increasing enzymatic (SOD, POD, and CAT) and non-enzymatic (AsA and non-protein thiols) antioxidants, MeJA pretreatment decreased lipid peroxidation, O2- and H2O2 accumulation and recovered photosynthetic pigment content under Pb stress. Increased osmolytes (proline, sugar, and starch) and protein content after MeJA pretreatment under Pb stress restore cellular homeostasis and improved kenaf tolerance. Our results suggest that MeJA pretreatment modifies the antioxidant machinery of kenaf and inhibits stress-related processes that cause lipid peroxidation, hence enhancing plant tolerance to Pb stress.

Morpho-physio-biochemical, molecular, and phytoremedial responses of plants to red, blue, and green light: a review.

Light is a basic requirement to drive carbon metabolism in plants and supports life on earth. Spectral quality greatly affects plant morphology, physiology, and metabolism of various biochemical pathways. Among visible light spectrum, red, blue, and green light wavelengths affect several mechanisms to contribute in plant growth and productivity. In addition, supplementation of red, blue, or green light with other wavelengths showed vivid effects on the plant biology. However, response of plants differs in different species and growing conditions. This review article provides a detailed view and interpretation of existing knowledge and clarifies underlying mechanisms that how red, blue, and green light spectra affect plant morpho-physiological, biochemical, and molecular parameters to make a significant contribution towards improved crop production, fruit quality, disease control, phytoremediation potential, and resource use efficiency.

Molecular-Assisted Breeding of Cadmium Pollution-Safe Cultivars.

Cadmium (Cd) contamination in edible agricultural products, especially in crops intended for consumption, has raised worldwide concerns regarding food safety. Breeding of Cd pollution-safe cultivars (Cd-PSCs) is an effective solution to preventing the entry of Cd into the food chain from contaminated agricultural soil. Molecular-assisted breeding methods, based on molecular mechanisms for cultivar-dependent Cd accumulation and bioinformatic tools, have been developed to accelerate and facilitate the breeding of Cd-PSCs. This review summarizes the recent progress in the research of the low Cd accumulation traits of Cd-PSCs in different crops. Furthermore, the application of molecular-assisted breeding methods, including transgenic approaches, genome editing, marker-assisted selection, whole genome-wide association analysis, and transcriptome, has been highlighted to outline the breeding of Cd-PSCs by identifying critical genes and molecular biomarkers. This review provides a comprehensive overview of the development of Cd-PSCs and the potential future for breeding Cd-PSC using modern molecular technologies.

Intercropping of kenaf and soybean affects plant growth, antioxidant capacity, and uptake of cadmium and lead in contaminated mining soil.

Intercropping is considered a sustainable agricultural practice that can reduce the environmental impacts on agriculture. Our study investigated the morphology, physiology, and cadmium (Cd) and lead (Pb) uptake of kenaf (Hibiscus cannabinus L.) and soybean (Glycine max L.) under intercropping in mining soil. Results showed that mutual intercropping is conducive to the growth and biomass accumulation of kenaf and soybean, compared to their respective monoculture. Intercropping increased the relative chlorophyll index in kenaf, while that in soybean had no significant effect. Furthermore, intercropping increased the antioxidant enzyme activity of kenaf, while that of soybean reduced or had no significant effect. The content of malondialdehyde (MDA) was decreased in both of the species. Compared to their respective monoculture, Cd content was increased in kenaf leaves and reduced in soybean roots. Moreover, intercropping decreased the Pb content in tissues of both the species, except that Pb content of kenaf roots was increased. At the same time, root, leaf, or stem bioconcentration factors also performed the same trend, and TF was less than 1. These results indicated that intercropping can increase the plant growth and decrease the metal content in plant tissues. Present findings could provide support for future research on kenaf and soybean cultivation in contaminated lands. In addition, the present study strengthens our understanding about the effectiveness of intercropping system on heavy metal-contaminated lands for sustainable agricultural production.

Physiological and DNA methylation analysis provides epigenetic insights into kenaf cadmium tolerance heterosis.

Soil heavy metal pollution is one of the most challenging problems. Kenaf is an important natural fiber crop with strong heterosis and a higher tolerance to heavy metals. However, little is known about the molecular mechanisms of kenaf heavy metal tolerance, especially the mechanism of genomic DNA methylation regulating heterosis. In this study, kenaf cultivars CP085, CP089, and their hybrid F1 seedlings were subjected to 300 µM cadmium stress and found obvious heterosis of cadmium resistance in morphology and antioxidant enzyme activity of F1 hybrid seedlings. Through methylation-sensitive amplification polymorphism (MSAP) analysis, we highlighted that the total DNA methylation level under cadmium decreased by 16.9 % in F1 and increased by 14.0 % and 3.0 % in parents CP085 and CP089, respectively. The hypomethylation rate was highest (21.84 %), but hypermethylation was lowest (17.24 %) in F1 compared to parent cultivars. In particular, principal coordinates analysis (PCoA) indicates a significant epigenetic differentiation between F1 and its parents under cadmium. Furthermore, 21 differentially methylated DNA fragments (DMFs) were analyzed. Especially, the expression of NPF2.7, NADP-ME, NAC71, TPP-D, LRR-RLKs, and DHX51 genes were changed due to cadmium stress and related to cytosine methylation regulation. Finally, the knocked-down of the differentially methylated gene NPF2.7 by virus-induced gene silencing (VIGS) resulted in increased sensitivity of kenaf seedlings under cadmium stress. It is speculated that low DNA methylation levels can regulate gene expression that led to the heterosis of cadmium tolerance in kenaf.

Calcium Nanoparticles Impregnated With Benzenedicarboxylic Acid: A New Approach to Alleviate Combined Stress of DDT and Cadmium in Brassica alboglabra by Modulating Bioacummulation, Antioxidative Machinery and Osmoregulators.

At present, the alleviation of stress caused by climate change and environmental contaminants is a crucial issue. Dichlorodiphenyltrichloroethane (DDT) is a persistent organic pollutant (POP) and an organochlorine, which causes significant health problems in humans. The stress caused by cadmium (Cd) and the toxicity of DDT have direct effects on the growth and yield of crop plants. Ultimately, the greater uptake and accumulation of DDT by edible plants affects human health by contaminating the food chain. The possible solution to this challenging situation is to limit the passive absorption of POPs into the plants. Calcium (Ca) is an essential life component mandatory for plant growth and survival. This study used impregnated Ca (BdCa) of benzenedicarboxylic acid (Bd) to relieve abiotic stress in plants of Brassica alboglabra. BdCa mitigated the deleterious effects of Cd and reduced DDT bioaccumulation. By increasing the removal efficacy (RE) up to 256.14%, BdCa greatly decreased pollutant uptake (Cd 82.37% and DDT 93.64%) and supported photosynthetic machinery (86.22%) and antioxidant enzyme defenses (264.73%), in applied plants. Exogenously applied Bd also successfully improved the antioxidant system and the physiochemical parameters of plants. However, impregnation with Ca further enhanced plant tolerance to stress. This novel study revealed that the combined application of Ca and Bd could effectively relieve individual and combined Cd stress and DDT toxicity in B. alboglabra.

Karrikinolide alleviates BDE-28, heat and Cd stressors in Brassica alboglabra by correlating and modulating biochemical attributes, antioxidative machinery and osmoregulators.

In this study, we have evaluated the role of karrikin (KAR1) against the absorption and translocation of a persistent organic pollutant (POP), 2,4,4'-Tribromodiphenyl ether (BDE-28) in plants, in the presence of two other stressors, cadmium (Cd) and high temperature. Furthermore, it correlates the physiological damages of Brassica alboglabra with the three stresssors separately. The results revealed that the post-germination application of KAR1 successfully augmented the growth (200%) and pertinent physiochemical parameters of B. alboglabra. KAR1 hindered air absorption of BDE-28 in plant tissues, and reduced its translocation coefficient (TF). Moreover, BDE-28 was the most negatively correlated (-0.9) stressor with chlorophyll contents, while the maximum mitigation by KAR1 was also achieved agaist BDE-28. The effect of temperature was more severe on soluble sugars (0.51), antioxidative machinery (-0.43), and osmoregulators (0.24). Cd exhibited a stronger inverse interrelation with the enzymatic antioxidant cascade. Application of KAR1 mitigated the deleterious effects of Cd and temperature stress on plant physiological parameters along with reduced aero-concentration factor, TF, and metal tolerance index. The phytohormone reduced lipid peroxidation by decreasing synthesis of ROS and persuading its breakdown. The stability of cellular membranes was perhaps due to the commotion of KAR1 as a growth-promoting phytohormone. In the same way, KAR1 supplementation augmented the membrane stability index, antioxidant defense factors, and removal efficiency of the pollutants. Consequently, the exogenously applied KAR1 can efficiently alleviate Cd stress, heat stress, and POP toxicity.

Evaluation of three wheat (Triticum aestivum L.) cultivars as sensitive Cd biomarkers during the seedling stage.

Sensitive seedling crops have been developed to monitor Cadmium (Cd) contamination in agricultural soil. In the present study, 18 parameters involving growth conditions and physiological performances were assessed to evaluate Cd-responses of three wheat (Triticum aestivum L.) cultivars, Xihan1 (XH), Longzhong1 (LZ) and Dingfeng16 (DF). Principle component analysis illustrated that Factor 1, representing growth performance, soluble sugar content and catalase activity, responded to the Cd treatments in a dose dependent manner, while Factor 2 represented by chlorophyll content and germinating root growth was mainly dependent on cultivar differences. Higher inhibition rates were observed in growth performance than in physiological responses, with the highest inhibition rates of shoot biomasses (39.6%), root length (58.7%), root tip number (57.8%) and bifurcation number (83.2%), even under the lowest Cd treatment (2.5 mg·L-1). According to the Cd toxicity sensitivity evaluation, DF exerted highest tolerance to Cd stress in root growth while LZ was more sensitive to Cd stress, suggesting LZ as an ideal Cd contaminant biomarker. This study will provide novel insight into the cultivar-dependent response during using wheat seedlings as Cd biomarkers.

Metabolic and Proteomic Perspectives of Augmentation of Nutritional Contents and Plant Defense in Vigna unguiculata.

The current study enlists metabolites of Alstonia scholaris with bioactivities, and the most active compound, 3-(1-methylpyrrolidin-2-yl) pyridine, was selected against Macrophomina phaseolina. Appraisal of the Alstonia metabolites identified the 3-(1-methylpyrrolidin-2-yl) pyridine as a bioactive compound which elevated vitamins and nutritional contents of Vigna unguiculata up to ≥18%, and other physiological parameters up to 28.9%. The bioactive compound (0.1%) upregulated key defense genes, shifted defense metabolism from salicylic acid to jasmonic acid, and induced glucanase enzymes for improved defenses. The structural studies categorized four glucanase-isozymes under beta-glycanases falling in (Trans) glycosidases with TIM beta/alpha-barrel fold. The study determined key-protein factors (Q9SAJ4) for elevated nutritional contents, along with its structural and functional mechanisms, as well as interactions with other loci. The nicotine-docked Q9SAJ4 protein showed a 200% elevated activity and interacted with AT1G79550.2, AT1G12900.1, AT1G13440.1, AT3G04120.1, and AT3G26650.1 loci to ramp up the metabolic processes. Furthermore, the study emphasizes the physiological mechanism involved in the enrichment of the nutritional contents of V. unguiculata. Metabolic studies concluded that increased melibiose and glucose 6-phosphate contents, accompanied by reduced trehalose (-0.9-fold), with sugar drifts to downstream pyruvate biosynthesis and acetyl Co-A metabolism mainly triggered nutritional contents. Hydrogen bonding at residues G.357, G.380, and G.381 docked nicotine with Q9SAJ4 and transformed its bilobed structure for easy exposure toward substrate molecules. The current study augments the nutritional value of edible stuff and supports agriculture-based country economies.

Comparative Transcriptome Analysis Revealed the Tissue-Specific Accumulations of Taxanes among Three Experimental Lines of Taxus yunnanensis.

Taxus yunnanensis (Yew) is known for natural anticancer metabolite paclitaxel (Taxol) and its biosynthesis pathway in yew species still needs to be completely elucidated. In the current study, productions of paclitaxel and 10-DAB III from three different tissues (needle, branch, and root) of T. yunnanensis wild type (WT) and two new cultivars Zhongda-1 (Zd1) and Zhongda-2 (Zd2) were determined, and significant tissue differences in contents of the taxanes were observed among the three experimental lines. The much higher 10-DAB III and lower paclitaxel contents in needle of Zd2 when compared with that of Zd1 indicated the low conversion from 10-DAB III to paclitaxel in the needle of Zd2. In order to uncover the mechanisms of the tissue-specific biosynthesis of the taxanes, transcriptome analysis of cultivar Zd2 was conducted, and the previously reported transcriptome data of Zd1 and WT were used to perform a comparison. The enhancement of TDAT and T10ßH side biosynthetic pathway in roots of Zd2 in early taxane synthesis might lead to the biosynthesis of other toxoids, while the preference of T13αH route in the needle and branch of Zd2 was mainly responsible for the tissue-specific reinforced biosynthesis of 10-DAB III and paclitaxel in Zd2. Different from Zd1, the tissue-specific pattern of paclitaxel biosynthesis genes in Zd2 was similar to WT. However, the lower transcript abundance of final steps genes (TBT, DBAT, BAPT, and DBTNBT) of the paclitaxel biosynthesis pathway in Zd2 than in Zd1 might further promote 10-DAB III accumulation in Zd2.

Transcriptome profiling reveals specific patterns of paclitaxel synthesis in a new Taxus yunnanensis cultivar.

The difference in contents of paclitaxel and 10-deacetylbaccatin III (10-DABIII) in needles between wildtype (WT) and a new cultivar (Zhongdayihao, ZD1) of Taxus yunnanensis was examined. Transcriptome profiling was conducted for different tissues of the ZD1 and WT to illustrate the regulation mechanism of paclitaxel biosynthesis. It was observed that average contents of paclitaxel and 10-DABIII in ZD1 were 4 folds and 32 folds higher than those in WT, respectively. More significant elevations of differential expressed genes (DEGs) from paclitaxel biosynthesis pathway were revealed in ZD1 rather than WT, which should be responsible for the higher contents of paclitaxel and 10-DABIII in the ZD1. Special tissues-dependent expression patterns of paclitaxel biosynthesis DEGs in ZD1 compared to WT were unraveled. The relative higher expressions of paclitaxel biosynthesis genes in needles than other tissues supported the higher content of paclitaxel and 10-DABIII content in needles of ZD1. Attenuation of plant hormone signal transduction pathway led to the lower expression of TFs in ZD1 rather than WT. Besides, the significant negative correlations between differential expressed TFs and DEGs from paclitaxel biosynthesis pathway displayed a possibly negative regulation pattern of these TFs on paclitaxel biosynthesis pathway genes. These results provided new insights into the molecular process of paclitaxel synthesis in Taxus.

Toxicity of cadmium and its health risks from leafy vegetable consumption.

Cadmium (Cd) is a highly toxic heavy metal and has spread widely in the environment in recent decades. This review summarizes current knowledge about Cd contamination of leafy vegetables, its toxicity, exposure, health risks, and approaches to reducing its toxicity in humans. Leafy vegetable consumption has been identified as a dominant exposure pathway of Cd in the human body. An overview of Cd pollution in leafy vegetables as well as the main sources of Cd is given. Notable estimated daily intakes and health risks of Cd exposure through vegetable consumption for humans are revealed in occupational exposure areas and even in some reference areas. Vegetable consumption is one of the most significant sources of exposure to Cd, particularly in occupational exposure regions. Therefore, numerous approaches have been developed to minimize the accumulation of Cd in leafy vegetables, among which the breeding of Cd pollution-safe cultivars is one of the most effective tools. Furthermore, dietary supplements from leafy vegetables perform positive roles in alleviating Cd toxicity in humans with regard to the effects of essential mineral elements, vitamins and phytochemicals taken into the human body via leafy vegetable consumption.

Comparative analysis of cadmium responsive microRNAs in roots of two Ipomoea aquatica Forsk. cultivars with different cadmium accumulation capacities.

In plants, microRNAs (miRNAs) play regulatory roles in response to various environmental stresses. In order to illustrate the regulation mechanisms of miRNAs involving the different Cd accumulation abilities between a low-shoot-Cd cultivar (QLQ) and a high-shoot-Cd cultivar (T308) of water spinach (Ipomoea aquatic Forsk.), six sRNA libraries at 3 different time points were constructed. Only 5 miRNAs were exclusively regulated in QLQ, among them, miRNA395 was up-regulated, which was supposed to enhance the Cd retention and detoxification in root. Also, the alterations of miRNA5139, miRNA1511 and miRNA8155 contributed to the attenuation of Cd translocation into the shoot of QLQ. More differentially expressed miRNAs were observed in T308, indicating more complex response was adopted by T308 under Cd stress. miRNA397 exclusively regulated in T308 has enhanced the Cd influx of T308 under Cd treatments. Besides, the Cd translocation of T308 was strengthened due to the up-regulation of MATE efflux family, which was targeted by miRNA3627. Our results unraveled the effects of the cultivar-dependent expression of these specific miRNAs on the different Cd accumulation and translocation abilities of QLQ and T308. These findings provide a new perspective for the molecular assisted breeding of low-Cd cultivars for leaf-vegetables.

Identification and characterization of rhizospheric microbial diversity by 16S ribosomal RNA gene sequencing.

In the present study, samples of rhizosphere and root nodules were collected from different areas of Pakistan to isolate plant growth promoting rhizobacteria. Identification of bacterial isolates was made by 16S rRNA gene sequence analysis and taxonomical confirmation on EzTaxon Server. The identified bacterial strains were belonged to 5 genera i.e. Ensifer, Bacillus, Pseudomona, Leclercia and Rhizobium. Phylogenetic analysis inferred from 16S rRNA gene sequences showed the evolutionary relationship of bacterial strains with the respective genera. Based on phylogenetic analysis, some candidate novel species were also identified. The bacterial strains were also characterized for morphological, physiological, biochemical tests and glucose dehydrogenase (gdh) gene that involved in the phosphate solublization using cofactor pyrroloquinolone quinone (PQQ). Seven rhizoshperic and 3 root nodulating stains are positive for gdh gene. Furthermore, this study confirms a novel association between microbes and their hosts like field grown crops, leguminous and non-leguminous plants. It was concluded that a diverse group of bacterial population exist in the rhizosphere and root nodules that might be useful in evaluating the mechanisms behind plant microbial interactions and strains QAU-63 and QAU-68 have sequence similarity of 97 and 95% which might be declared as novel after further taxonomic characterization.

Identification and characterization of rhizospheric microbial diversity by 16S ribosomal RNA gene sequencing

In the present study, samples of rhizosphere and root nodules were collected from different areas of Pakistan to isolate plant growth promoting rhizobacteria. Identification of bacterial isolates was made by 16S rRNA gene sequence analysis and taxonomical confirmation on EzTaxon Server. The identified bacterial strains were belonged to 5 genera i.e. Ensifer, Bacillus, Pseudomona, Leclercia and Rhizobium. Phylogenetic analysis inferred from 16S rRNA gene sequences showed the evolutionary relationship of bacterial strains with the respective genera. Based on phylogenetic analysis, some candidate novel species were also identified. The bacterial strains were also characterized for morphological, physiological, biochemical tests and glucose dehydrogenase (gdh) gene that involved in the phosphate solublization using cofactor pyrroloquinolone quinone (PQQ). Seven rhizoshperic and 3 root nodulating stains are positive for gdh gene. Furthermore, this study confirms a novel association between microbes and their hosts like field grown crops, leguminous and non-leguminous plants. It was concluded that a diverse group of bacterial population exist in the rhizosphere and root nodules that might be useful in evaluating the mechanisms behind plant microbial interactions and strains QAU-63 and QAU-68 have sequence similarity of 97 and 95% which might be declared as novel after further taxonomic characterization.