Understanding the Molecular Regulatory Networks of Seed Size in Soybean.

Soybean being a major cash crop provides half of the vegetable oil and a quarter of the plant proteins to the global population. Seed size traits are the most important agronomic traits determining the soybean yield. These are complex traits governed by polygenes with low heritability as well as are highly influenced by the environment as well as by genotype x environment interactions. Although, extensive efforts have been made to unravel the genetic basis and molecular mechanism of seed size in soybean. But most of these efforts were majorly limited to QTL identification, and only a few genes for seed size were isolated and their molecular mechanism was elucidated. Hence, elucidating the detailed molecular regulatory networks controlling seed size in soybeans has been an important area of research in soybeans from the past decades. This paper describes the current progress of genetic architecture, molecular mechanisms, and regulatory networks for seed sizes of soybeans. Additionally, the main problems and bottlenecks/challenges soybean researchers currently face in seed size research are also discussed. This review summarizes the comprehensive and systematic information to the soybean researchers regarding the molecular understanding of seed size in soybeans and will help future research work on seed size in soybeans.

Nitric oxide mitigates vanadium toxicity in soybean (Glycine max L.) by modulating reactive oxygen species (ROS) and antioxidant system.

Vanadium (V) induced hazardous effects posturing a serious concern on crop production as well as food security. However, the nitric oxide (NO)-mediated alleviation of V-induced oxidative stress in soybean seedlings is still unknown. Therefore, this research was designed to explore the effects of exogenous NO to mitigate the V-induced phytotoxicity in soybean plants. Our upshots disclosed that NO supplementation considerably improved the plant biomass, growth, and photosynthetic attributes by regulating the carbohydrates, and plants biochemical composition, which further improved the guard cells, and stomatal aperture of soybean leaves. Additionally, NO regulated the plant hormones, and phenolic profile which restricted the V contents absorption (65.6%), and translocation (57.9%) by maintaining the nutrient acquisition. Furthermore, it detoxified the excessive V contents, and upsurged the antioxidants defense mechanism to lower the MDA, and scavenge ROS production. The molecular analysis further verified the NO-based regulation of lipid, sugar production, and degradation as well as detoxification mechanism in the soybean seedlings. Exclusively, we elaborated very first time the behind mechanism of V-induced oxidative stress alleviation by exogenous NO, hence illustrating the NO supplementation role as a stress alleviating agent for soybean grown in V contaminated areas to elevate the crop development and production.

Mitigation of Negative Effects of Chromium (VI) Toxicity in Faba Bean (Vicia faba) Plants through the Supplementation of Kinetin (KN) and Gibberellic Acid (GA3).

The present study was carried out to explore the possible role of kinetin and gibberellic acid (GA3) on faba bean under chromium (Cr) stress. Cr treatment negatively affected growth and biomass production, reduced photosynthetic pigments, and inhibited photosynthesis, gas exchange parameters, antioxidant enzymes, and the glyoxylase cycle. Moreover, Cr stress enhanced the production of malondialdehyde (MDA, 216.11%) and hydrogen peroxide (H2O2, 230.16%), electrolyte leakage (EL, 293.30%), and the accumulation of proline and glycine betaine. Exogenous application of kinetin and GA3 increased growth and biomass, improved pigment contents and photosynthesis, as well as up-regulated the antioxidant system by improving the antioxidant enzyme activities and the content of nonenzymatic components, and the glyoxylase cycle. Additionally, kinetin and GA3 application displayed a considerable enhancement in proline (602.61%) and glycine betaine (423.72), which help the plants to maintain water balance under stress. Furthermore, a decline in Cr uptake was also observed due to kinetin and GA3 application. Exogenous application of kinetin and GA3 ameliorated the toxic effects of Cr in faba bean plants, up-shooting the tolerance mechanisms, including osmolyte metabolism and the antioxidant system.

Brassinosteroid Supplementation Alleviates Chromium Toxicity in Soybean (Glycine max L.) via Reducing Its Translocation.

Chromium (Cr) phytotoxicity severely inhibits plant growth and development which makes it a prerequisite to developing techniques that prevent Cr accumulation in food chains. However, little is explored related to the protective role of brassinosteroids (BRs) against Cr-induced stress in soybean plants. Herein, the morpho-physiological, biochemical, and molecular responses of soybean cultivars with/without foliar application of BRs under Cr toxicity were intensely investigated. Our outcomes deliberated that BRs application noticeably reduced Cr-induced phytotoxicity by lowering Cr uptake (37.7/43.63%), accumulation (63.92/81.73%), and translocation (26.23/38.14%) in XD-18/HD-19, plant tissues, respectively; besides, improved seed germination ratio, photosynthetic attributes, plant growth, and biomass, as well as prevented nutrient uptake inhibition under Cr stress, especially in HD-19 cultivar. Furthermore, BRs stimulated antioxidative defense systems, both enzymatic and non-enzymatic, the compartmentalization of ion chelation, diminished extra production of reactive oxygen species (ROS), and electrolyte leakage in response to Cr-induced toxicity, specifically in HD-19. In addition, BRs improved Cr stress tolerance in soybean seedlings by regulating the expression of stress-related genes involved in Cr accumulation, and translocation. Inclusively, by considering the above-mentioned biomarkers, foliar spray of BRs might be considered an effective inhibitor of Cr-induced damages in soybean cultivars, even in Cr polluted soil.

Chromium toxicity induced oxidative damage in two rice cultivars and its mitigation through external supplementation of brassinosteroids and spermine.

The chromium (Cr) induced phytotoxicity avowed the scientific community to develop stress mitigation strategies to restrain the Cr accumulation inside the food chain. Whereas, brassinosteroids (BRs), and spermine (SPM) are well-known growth-promoting phytohormones, which enhance the plants health, and resilient the toxic effects under stress conditions. Until now, their interactive role against Cr-mitigation is poorly known. Hence, we conducted the hydroponic experiment to perceive the behavior of seed primed with BRs, or/and SPM treatment against Cr disclosure in two different rice cultivars (CY927; sensitive, YLY689; tolerant). Our findings delineated that BRs (0.01 µM), or/and SPM (0.01 mM) remarkably alleviated Cr-induced phytotoxicity by improving the seed germination ratio, chlorophyll pigments, PSII system, total soluble sugar, and minimizing the MDA contents level, ROS extra generation, and electrolyte leakage through restricting the Cr accretion in roots, and shoots of both rice cultivars under Cr stress. Additionally, the BRs, or/and SPM modulated the antioxidant enzyme, and non-enzyme activities to reduce the Cr-induced cellular oxidative damage as well as maintained the ionic hemostasis in both rice cultivars, especially in YLY689. Concisely, enhanced the plants biomass and growth. Overall, our outcomes revealed that BRs and SPM interact positively to alleviate the Cr-induced damages in rice seedlings on the above-mentioned indices, and combine treatment is much more efficient than solely. Moreover, the effect of BRs, or/and SPM was more obvious in YLY689 than CY927 to hamper the oxidative stress, and boost the antioxidant capacity.

Defense interplay of the zinc-oxide nanoparticles and melatonin in alleviating the arsenic stress in soybean (Glycine max L.).

Present study showed the successful application of the modified hydrothermal method for synthesizing the zinc oxide nanoparticles (ZnO-NPs) efficiently. Well as-synthesized ZnO-NPs are analyzed for various techniques viz., X-ray diffraction (XRD), SEM micrographs, EDAX/Mapping pattern, Raman Spectroscopy Pattern, UV, Photoluminescence (PL) and X-ray photoemission spectroscopy (XPS) analysis. All these measurements showed that ZnO-NPs are highly pure with no internal defects, and can be potentially used in the plant applications. Hence, we further determined the effect of these nanoparticles and melatonin for the modulation of the As tolerance in soybean plants by examining the various growth attributes and metabolic parameters. Our results demonstrated that As-stress inhibited growth (∼34%), photosynthesis-related parameters (∼18-28%) and induced ROS accumulation; however, all these attributes are substantially reversed by the ZnO-NPs and melatonin treatments. Moreover, the As stress induced malondialdehyde (MDA; 71%) and hydrogen peroxide (H2O2; 82%) are partially reversed by the ZnO-NPs and melatonin in the As-stressed plants. This might have resulted due to the ZnO-NPs and melatonin induced activities of the antioxidants plant defense. Overall, the ZnO-NPs and melatonin supplementation separately and in combination positively regulated the As tolerance in soybean; however, the effect of their combined application on the As tolerance was more profound relative to the individual application. These results suggested the synergetic effect of the ZnO-NPs and melatonin on the As tolerance in soybean. However, the in-depth mechanism underlying the defense crosstalk between the ZnO-NPs and melatonin needs to be further explored.

Newly-synthesized iron-oxide nanoparticles showed synergetic effect with citric acid for alleviating arsenic phytotoxicity in soybean.

In the current investigation, we presented the success of the modified hydrothermal method for synthesizing the iron-oxide nanoparticles (Fe2O3-NPs) efficiently. These NPs were further characterized by using different techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) micrographs, energy-dispersive X-ray spectroscopy (EDAX)/Mapping pattern, Raman Spectroscopy Pattern, ultra violet (UV) and Photoluminescence (PL). All these analyses revealed highly pure nature of Fe2O3-NPs with no internal defects, and suggested its application for plant growth improvement. Therefore, we further investigated the separate as well as combined effects of the Fe2O3-NPs and citric acid (CA) in the alleviation of arsenic (As) toxicity in the soybean (Glycine max L.), by evaluating the different plant growth and metabolic attributes. Results of our study revealed that As-induced growth inhibition, reduction of photosynthesis, water use efficiency (WUE), and reactive oxygen species (ROS) accumulation whereas application of the Fe2O3-NPs and CA significantly reversed all these adverse effects in soybean plants. Moreover, the As-stress induced malondialdehyde (MDA) and hydrogen peroxide (H2O2) production were partially reversed by the Fe2O3-NPs and CA in the As-stressed plants by 16% and 10% (MDA) and 29% and 12% (H2O2). This might have resulted due to the Fe2O3-NPs and CA induced activities of the antioxidant defense in plants. Overall, the Fe2O3-NPs and CA supplementation separately and in combination positively regulated the As tolerance in soybean; however, the effect of the combined application on the As tolerance was more profound relative to the individual application. These results suggested the synergetic effect of the Fe2O3-NPs and CA on the As-tolerance in soybean. However, in-depth mechanism underlying the defense crosstalk between the Fe2O3-NPs and CA needs to be further explored.

Zinc oxide nanoparticles alleviates the adverse effects of cadmium stress on Oryza sativa via modulation of the photosynthesis and antioxidant defense system.

Cadmium (Cd) is a trace element causing severe toxicity symptoms in plants, besides posing hazardous fitness issue due to its buildup in the human body through food chain. Nanoparticles (NPs) are recently employed as a novel strategy to directly ameliorate the Cd stress and acted as nano-fertilizers. The intend of the current study was to explore the effects of zinc oxide nanoparticles (ZnO-NPs; 50 mg/L) on plant growth, photosynthetic activity, elemental status and antioxidant activity in Oryza sativa (rice) under Cd (0.8 mM) stress. To this end, the rice plants are treated by Cd stress at 15 days after sowing (DAS), and the treatment was given directly into the soil. Supply of ZnO-NPs as foliar spray was given for five consecutive days from 30 to 35 DAS, and sampling was done at 45 DAS. However, rice plants supplemented with ZnO-NPs under the Cd toxicity revealed significantly increased shoot length (SL; 34.0%), root fresh weight (RFW; 30.0%), shoot dry weight (SDW; 23.07%), and root dry weight (RDW; 12.24%). Moreover, the ZnO-NPs supplement has also positive effects on photosynthesis related parameters, SPAD value (40%), chloroplast structure, and qualitatively high fluorescence observed by confocal microscopy even under Cd stress. ZnO-NPs also substantially prevented the increases of hydrogen peroxide (H2O2) and malondialdehyde (MDA) triggered by Cd. Physiological and biochemical analysis showed that ZnO-NPs increased enzymatic activities of superoxide dismutase (SOD; 59%), catalase (CAT; 52%), and proline (17%) that metabolize reactive oxygen species (ROS); these increases coincided with the changes observed in the H2O2 and MDA accumulation after ZnO-NPs application. In conclusion, ZnO-NPs application to foliage has great efficiency to improve biomass, photosynthesis, protein, antioxidant enzymes activity, mineral nutrient contents and reducing Cd levels in rice. This can be attributed mainly from reduced oxidative damage resulted due to the ZnO-NPs application.

Biochar supplementation regulates growth and heavy metal accumulation in tomato grown in contaminated soils.

Biochar application has recently gained increased attention to reclaim heavy metal degraded soils. In this context, the present study investigated the effects of biochar on the growth regulation and heavy metal accumulation in tomato grown on contaminated soils. A two-factorial design with factor A including three treatments with mine (contaminated soil) and garden soil in the following ratio viz., T1 = 1:2, T2 = 1:1, and T3 = 2:1, and garden soil only as control; whereas factor B consists of biochar amendments at three levels viz., B1 (3%), B2 (6%), and B3 (9%). Our results revealed significant negative effects of heavy metal-contaminated soil on plant growth, and besides resulted heavy metal accumulation in tomato fruit. Tomato plants showed maximum reduction of growth in T3 followed by T2, and lowest in T1, a similar pattern was found for accumulation of heavy metals in the fruit. However, the application of biochar reduced the bioavailability and accumulation of heavy metals in the tomato fruit, as well as improved plant growth in contaminated soils. Overall, among the three biochar treatments, B2 was determined as the optimum level for improved growth coupled with reduced heavy metal accumulation in the tomato fruit. Besides, biochar application decreased the daily intake of metals and human health risk index values, thus alleviating the health risk. Hence, the present study demonstrated a positive role of biochar in reclaiming heavy metal-contaminated soils and in increasing the plant growth.

Auxin metabolic network regulates the plant response to metalloids stress.

Metalloids are among the major pollutants posing a risk to the environment and global food security. Plant roots uptake these toxic metalloids from the soil along with other essential minerals. Plants respond to metalloid stress by regulating the distribution and levels of various endogenous phytohormones. Recent research showed that auxin is instrumental in mediating resilience to metalloid-induced stress in plants. Exogenous supplementation of the auxin or plant growth-promoting micro-organisms (PGPMs) alleviates metalloid uptake, localization, and accumulation in the plant tissues, thereby improving plant growth under metalloid stress. Moreover, auxin triggers various biological responses such as the production of enzymatic and non-enzymatic antioxidants to combat nitro-oxidative stress induced by the metalloids. However, an in-depth understanding of the auxin stimulated molecular and physiological responses to the metalloid toxicity needs to be investigated in future studies. The current review attempts to provide an update on the recent advances and the current state-of-the-art associated with auxin and metalloid interaction, which could be used as a start point to develop biotechnological tools and create an eco-friendly environment.

Role of Silicon in Mitigation of Heavy Metal Stresses in Crop Plants.

Over the past few decades, heavy metal contamination in soil and water has increased due to anthropogenic activities. The higher exposure of crop plants to heavy metal stress reduces growth and yield, and affect the sustainability of agricultural production. In this regard, the use of silicon (Si) supplementation offers a promising prospect since numerous studies have reported the beneficial role of Si in mitigating stresses imposed by biotic as well as abiotic factors including heavy metal stress. The fundamental mechanisms involved in the Si-mediated heavy metal stress tolerance include reduction of metal ions in soil substrate, co-precipitation of toxic metals, metal-transport related gene regulation, chelation, stimulation of antioxidants, compartmentation of metal ions, and structural alterations in plants. Exogenous application of Si has been well documented to increase heavy metal tolerance in numerous plant species. The beneficial effects of Si are particularly evident in plants able to accumulate high levels of Si. Consequently, to enhance metal tolerance in plants, the inherent genetic potential for Si uptake should be improved. In the present review, we have discussed the potential role and mechanisms involved in the Si-mediated alleviation of metal toxicity as well as different approaches for enhancing Si-derived benefits in crop plants.

Genome-Wide Detection of Major and Epistatic Effect QTLs for Seed Protein and Oil Content in Soybean Under Multiple Environments Using High-Density Bin Map.

Seed protein and oil content are the two important traits determining the quality and value of soybean. Development of improved cultivars requires detailed understanding of the genetic basis underlying the trait of interest. However, it is prerequisite to have a high-density linkage map for precisely mapping genomic regions, and therefore the present study used high-density genetic map containing 2267 recombination bin markers distributed on 20 chromosomes and spanned 2453.79 cM with an average distance of 1.08 cM between markers using restriction-site-associated DNA sequencing (RAD-seq) approach. A recombinant inbred line (RIL) population of 104 lines derived from a cross between Linhefenqingdou and Meng 8206 cultivars was evaluated in six different environments to identify main- and epistatic-effect quantitative trait loci (QTLs)as well as their interaction with environments. A total of 44 main-effect QTLs for protein and oil content were found to be distributed on 17 chromosomes, and 15 novel QTL were identified for the first time. Out of these QTLs, four were major and stable QTLs, viz., qPro-7-1, qOil-8-3, qOil-10-2 and qOil-10-4, detected in at least two environments plus combined environment with R² values >10%. Within the physical intervals of these four QTLs, 111 candidate genes were screened for their direct or indirect involvement in seed protein and oil biosynthesis/metabolism processes based on gene ontology and annotation information. Based on RNA sequencing (RNA-seq) data analysis, 15 of the 111 genes were highly expressed during seed development stage and root nodules that might be considered as the potential candidate genes. Seven QTLs associated with protein and oil content exhibited significant additive and additive × environment interaction effects, and environment-independent QTLs revealed higher additive effects. Moreover, three digenic epistatic QTLs pairs were identified, and no main-effect QTLs showed epistasis. In conclusion, the use of a high-density map identified closely linked flanking markers, provided better understanding of genetic architecture and candidate gene information, and revealed the scope available for improvement of soybean quality through marker assisted selection (MAS).