Metabolic Responses to Manganese Toxicity in Soybean Roots and Leaves

The key metabolic pathway of roots and leaves responses in Arachis hypogaea under Al toxicity stress

BACKGROUND

Aluminum (Al) toxicity inhibits plant growth and alters gene expression and metabolite profiles. However, the molecular mechanisms underlying the effects of Al toxicity on peanut plants remain unclear. Transcriptome and metabolome analyses were conducted to investigate the responses of peanut leaves and roots to Al toxicity.

RESULTS

Al toxicity significantly inhibited peanut growth, disrupted antioxidant enzyme systems in roots and leaves, and impaired nutrient absorption. Under Al toxicity stress, the content of indole-3-acetic acid-aspartate (IAA-Asp) decreased by 23.94% in leaves but increased by 12.91% in roots. Methyl jasmonate (MeJA) levels in leaves increased dramatically by 2642.86%. Methyl salicylate (MeSA) content in leaves and roots increased significantly by 140.00% and 472.22%, respectively. Conversely, isopentenyl adenosine (IPA) content decreased by 78.95% in leaves and 20.66% in roots. Transcriptome analysis identified 5831 differentially expressed genes (DEGs) in leaves and 6405 DEGs in roots, whereas metabolomics analysis revealed 210 differentially accumulated metabolites (DAMs) in leaves and 240 DAMs in roots. Under Al toxicity stress, both leaves and roots were significantly enriched in the "linoleic acid metabolism" pathway. Genes such as lipoxygenase LOX1-5 and LOX2S were differentially expressed, and metabolites, including linoleic acid and its oxidized derivatives, were differentially accumulated, mitigating oxidative stress.

CONCLUSIONS

This study elaborates on the potential complex physiological and molecular mechanisms of peanuts under aluminum toxicity stress, and highlights the importance of linoleic acid metabolism in coping with aluminum toxicity. These findings enhance our understanding of the impact of aluminum toxicity on peanut development and the response of key metabolic pathways, providing potential molecular targets for genetic engineering to improve crop resistance to aluminum stress.

Combined metabolomic and transcriptomic analysis to reveal the response of rice to Mn toxicity stress

Excessive manganese (Mn) concentrations affect plant gene expression, alter metabolite content, and impede plant growth. Rice plants are particularly susceptible to Mn toxicity stress in acidic soil; however, the underlying molecular mechanisms are so far unclear. This study used transcriptomic and metabolomic sequencing to examine roots and leaves of rice plants subjected to Mn toxicity stress. The findings showed that high Mn stress increased the content of malondialdehyde, proline, and soluble sugar in rice roots by 262.28 %, 803.37 %, and 167.25 %, respectively. In rice roots, the enzymatic activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) elevated by 119.69 %, 408.44 %, 151.97 %, and 27.19 %, respectively. In rice leaves, the proline content increased by 632.45 %, whereas the enzymatic activities of POD, SOD, CAT, and APX were elevated by 167.17 %, 14.08 %, 103.60 %, and 146.74 %, respectively. Mn toxicity stress decreased soluble protein content in rice roots, and in the leaves, it reduced the soluble protein, soluble sugar, and chlorophyll contents. In addition, Mn toxicity led to reduced biomass accumulation, plant height, stem diameter, and root growth. The contents of salicylic acid (increased by 118.40 % in roots and 66.38 % in leaves) and jasmonic acid (decreased by 50.18 % in roots and increased by 143.97 % in leaves) were also affected. Transcriptome analysis identified differentially expressed genes associated with transcription factors, antioxidant enzymes, and metal transporters. Metabolomics revealed 176 and 214 different metabolites in the roots and leaves, respectively, that under Mn toxicity stress affected major metabolic pathways associated with fatty and amino acids. The phenylalanine metabolism pathway was significantly enriched in both the roots and leaves. Combined transcriptomic and metabolomic analyses revealed three key pathways: lysine degradation and phenylpropanoid biosynthesis in roots and alpha-linolenic acid metabolism in leaves. Metabolic substances and genes associated with metabolic enzymes were identified. These results enhance our understanding of the molecular processes underlying the responses of rice to Mn toxicity stress and provide a basis for breeding Mn-tolerant rice varieties.

Silicon efficacy for the remediation of metal contaminated soil

In the course of past two decade anthropogenic activities have reinforced, begetting soil and water defilement. A plethora of heavy metals alters and limits plant growth and yield, with opposing effect on agricultural productivity. Silicon often perceived as plant alimentary 'nonentity'. A suite of determinants associated with silicon have been lately discerned, concerning plant physiology, chemistry, gene regulation/expression and interaction with different organisms. Exogenous supplementation of silicon renders resistance against heavy-metal stress. Predominantly, plants having significant amount of silicon in root and shoot thus are barely prone to pest onset and manifest greater endurance against abiotic stresses including heavy-metal toxicity. Silicon-mediated stress management involves abatement of metal ions within soil, co-precipitation of metal ions, gene modulation associated with metal transport, chelation, activation of antioxidants (enzymatic and non-enzymatic), metal ion compartmentation and structural metamorphosis in plants. Silicon supplementation also stimulates expression of stress-resistant genes under heavy-metal toxicity to provide plant tolerance under stress conditions. Ergo, to boost metal tolerance within crops, immanent genetic potential for silicon assimilation should be enhanced. Current study, addresses the potential role and mechanistic interpretation of silicon induced mitigation of heavy-metal stress in plants.

The mechanism of arbuscular mycorrhizal fungi-alleviated manganese toxicity in plants: A review

The development of the mining industry and the overuse of inorganic fertilizers have led to an excess of manganese (Mn) in the soil, thereby, contaminating the soil environment and people's health. On heavy metal-contaminated soils, the combined arbuscular mycorrhizal fungi (AMF)-phytoremediation technique becomes a hotspot because of its environmentally friendly, in situ remediation. AMF inoculation often leads to a decrease in host Mn acquisition, which provides a basis for its application in phytoremediation of contaminated soils. Moreover, the utilization value of native AMF is greater than that of exotic AMF, because native AMF can adapt better to Mn-contaminated soils. In addition to the fact that AMF enhance plant Mn tolerance responses such as regionalization, organic matter chelation, limiting uptake and efflux, and so on, AMF also develop plant-independent fungal pathways such as direct biosorption of Mn by mycorrhizal hyphae, fungal Mn transporter genes, and sequestration of Mn by mycorrhizal hyphae, glomalin, and arbuscule-containing root cortical cells, which together mitigate excessive Mn toxicity to plants. Clarifying AMF-plant interactions under Mn stress will provide support for utilizing AMF as a phytoremediation in Mn-contaminated soils. The review reveals in detail how AMF develop its own mechanisms for responding to excess Mn and how AMF enhance plant Mn tolerance, accompanied by perspectives for future research.

The Physiological Response Mechanism of Peanut Leaves under Al Stress

Aluminum (Al) toxicity in acidic soils can significantly reduce peanut yield. The physiological response of peanut leaves to Al poisoning stress still has not been fully explored. This research examined the influences of Al toxicity on peanut leaves by observing the leaf phenotype, scanning the leaf area and perimeter, and by measuring photosynthetic pigment content, physiological response indices, leaf hormone levels, and mineral element accumulation. Fluorescence quantitative RT-PCR (qPCR) was utilized to determine the relative transcript level of specific genes. The results indicated that Al toxicity hindered peanut leaf development, reducing their biomass, surface area, and perimeter, although the decrease in photosynthetic pigment content was minimal. Al toxicity notably affected the activity of antioxidative enzymes, proline content, and MDA (malondialdehyde) levels in the leaves. Additionally, Al poisoning resulted in the increased accumulation of iron (Fe), potassium (K), and Al in peanut leaves but reduced the levels of calcium (Ca), manganese (Mn), copper (Cu), zinc (Zn), and magnesium (Mg). There were significant changes in the content of hormones and the expression level of genes connected with hormones in peanut leaves. High Al concentrations may activate cellular defense mechanisms, enhancing antioxidative activity to mitigate excess reactive oxygen species (ROS) and affecting hormone-related gene expression, which may impede leaf biomass and development. This research aimed to elucidate the physiological response mechanisms of peanut leaves to Al poisoning stress, providing insights for breeding new varieties resistant to Al poisoning.

Metabolomics and physio-chemical analyses of mulberry plants leaves response to manganese deficiency and toxicity reveal key metabolites and their pathways in manganese tolerance

Introduction

Manganese (Mn) plays a pivotal role in plant growth and development. Aside aiding in plant growth and development, Mn as heavy metal (HM) can be toxic in soil when applied in excess. Morus alba is an economically significant plant, capable of adapting to a range of environmental conditions and possessing the potential for phytoremediation of contaminated soil by HMs. The mechanism by which M. alba tolerates Mn stresses remains obscure.

Methods

In this study, Mn concentrations comprising sufficiency (0.15 mM), higher regimes (1.5 mM and 3 mM), and deficiency (0 mM and 0.03 mM), were applied to M. alba in pot treatment for 21 days to understand M. alba Mn tolerance. Mn stress effects on the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intercellular CO2 concentration (Ci), chlorophyll content, plant morphological traits, enzymatic and non-enzymatic parameters were analyzed as well as metabolome signatures via non-targeted LC-MS technique.

Results

Mn deficiency and toxicity decrease plant biomass, Pn, Ci, Gs, Tr, and chlorophyll content. Mn stresses induced a decline in the activities of catalase (CAT) and superoxide dismutase (SOD), while peroxidase (POD) activity, and leaf Mn content, increased. Soluble sugars, soluble proteins, malondialdehyde (MDA) and proline exhibited an elevation in Mn deficiency and toxicity concentrations. Metabolomic analysis indicates that Mn concentrations induced 1031 differentially expressed metabolites (DEMs), particularly amino acids, lipids, carbohydrates, benzene and derivatives and secondary metabolites. The DEMs are significantly enriched in alpha-linolenic acid metabolism, biosynthesis of unsaturated fatty acids, galactose metabolism, pantothenate and CoA biosynthesis, pentose phosphate pathway, carbon metabolism, etc.

Discussion and conclusion

The upregulation of Galactinol, Myo-inositol, Jasmonic acid, L-aspartic acid, Coproporphyrin I, Trigonelline, Pantothenol, and Pantothenate and their significance in the metabolic pathways makes them Mn stress tolerance metabolites in M. alba. Our findings reveal the fundamental understanding of DEMs in M. alba's response to Mn nutrition and the metabolic mechanisms involved, which may hold potential significance for the advancement of M. alba genetic improvement initiatives and phytoremediation programs.

Genome-Wide Identification of OsZIPs in Rice and Gene Expression Analysis under Manganese and Selenium Stress

Zinc (Zn)- and iron (Fe)-regulating transport-like proteins (ZIPs) are a class of proteins crucial for metal uptake and transport in plants, particularly for Zn and Fe absorption and distribution. These proteins ensure the balance of trace elements essential for plant growth, development, and metabolic activities. However, the role of the rice (Oryza sativa) OsZIP gene family in manganese (Mn) and selenium (Se) transport remains underexplored. This research conducted an all-sided analysis of the rice OsZIPs and identified 16 OsZIP sequences. Phylogenetic analysis categorized the OsZIPs predominantly within the three subfamilies. The expression levels of OsZIPs in rice root and leaf subjected to Mn and Se toxicity stress were examined through quantitative real-time PCR (qRT-PCR). The findings revealed significant differential expression of many OsZIPs under these conditions, indicating a potential regulating effect in the response of rice to Mn and Se toxicity. This work lays a foundation for further functional studies of OsZIPs, enhancing our understanding of the response mechanisms of rice to Mn and Se toxicity and their roles in growth, development, and environmental adaptation.

Physiological Mechanism through Which Al Toxicity Inhibits Peanut Root Growth

Al (Aluminum) poisoning is a significant limitation to crop yield in acid soil. However, the physiological process involved in the peanut root response to Al poisoning has not been clarified yet and requires further research. In order to investigate the influence of Al toxicity stress on peanut roots, this study employed various methods, including root phenotype analysis, scanning of the root, measuring the physical response indices of the root, measurement of the hormone level in the root, and quantitative PCR (qPCR). This research aimed to explore the physiological mechanism underlying the reaction of peanut roots to Al toxicity. The findings revealed that Al poisoning inhibits the development of peanut roots, resulting in reduced biomass, length, surface area, and volume. Al also significantly affects antioxidant oxidase activity and proline and malondialdehyde contents in peanut roots. Furthermore, Al toxicity led to increased accumulations of Al and Fe in peanut roots, while the contents of zinc (Zn), cuprum (Cu), manganese (Mn), kalium (K), magnesium (Mg), and calcium (Ca) decreased. The hormone content and related gene expression in peanut roots also exhibited significant changes. High concentrations of Al trigger cellular defense mechanisms, resulting in differentially expressed antioxidase genes and enhanced activity of antioxidases to eliminate excessive ROS (reactive oxygen species). Additionally, the differential expression of hormone-related genes in a high-Al environment affects plant hormones, ultimately leading to various negative effects, for example, decreased biomass of roots and hindered root development. The purpose of this study was to explore the physiological response mechanism of peanut roots subjected to aluminum toxicity stress, and the findings of this research will provide a basis for cultivating Al-resistant peanut varieties.

Genome-Wide Identification of AhMDHs and Analysis of Gene Expression under Manganese Toxicity Stress in Arachis hypogaea

Malate dehydrogenase (MDH) is one kind of oxidation-reduction enzyme that catalyzes the reversible conversion of oxaloacetic acid to malic acid. It has vital functions in plant development, photosynthesis, abiotic stress responses, and so on. However, there are no reports on the genome-wide identification and gene expression of the MDH gene family in Arachis hypogaea. In this study, the MDH gene family of A. hypogaea was comprehensively analyzed for the first time, and 15 AhMDH sequences were identified. According to the phylogenetic tree analysis, AhMDHs are mainly separated into three subfamilies with similar gene structures. Based on previously reported transcriptome sequencing results, the AhMDH expression quantity of roots and leaves exposed to manganese (Mn) toxicity were explored in A. hypogaea. Results revealed that many AhMDHs were upregulated when exposed to Mn toxicity, suggesting that those AhMDHs might play an important regulatory role in A. hypogaea's response to Mn toxicity stress. This study lays foundations for the functional study of AhMDHs and further reveals the mechanism of the A. hypogaea signaling pathway responding to high Mn stress.