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Plant Secondary Metabolites Biosynthesis, Biological Activities and Transcriptional Regulation in Response to Abiotic/Biotic Stresses

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A special issue of Metabolites (ISSN 2218-1989). This special issue belongs to the section "Plant Metabolism".

Deadline for manuscript submissions: closed (15 August 2023) | Viewed by 10383

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Special Issue Editor

Dr. Muhammad Junaid Rao

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Guest Editor

College of Agriculture, Guangxi University, Nanning 530004, China
Interests: phenolic compounds; flavonoids; lignins; anthocyanins; abiotic stress; biotic stress; antioxidants; secondary metabolites; wax; volatile organic compounds
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the diversification of plants, tens of thousands of plant secondary metabolites (PSMs) evolve, which adapt to their changing surroundings. These metabolites play dominant roles in the interactions between plants and other organisms and endow plants with resistance to pathogens, insects, other herbivores, and abiotic stresses, such as cold/freeze, heavy metal, drought, salt, highlight, ultraviolet, heat, etc. The biological functions and transcriptional regulation of these PSMs have been investigated in model plants; however, fewer advancements have been achieved in cultivated crops. These are worthy of more attention as PSMs usually confer color, smell, taste, and tolerance to abiotic and biotic stresses and enhance the nutritional and health values to grains, fruits, vegetables, teas, herbs, and medicinal and ornamental plants.

This Special Issue is aimed at providing the latest research on plant secondary metabolites and advances in the biosynthesis, transcriptional regulation, and characterization, including new technologies, methods, and their interaction with abiotic and biotic tolerance.

Potential topics include but are not limited to:

Discoveries of new PSMs and their biosynthetic pathways;
Transcriptional regulation of PSMs and their antioxidant activities;
PSM regulation and storage in different organs of plants and their interaction with the environment;
PSM role in abiotic and abiotic stress tolerance;
Origin, evolution, and domestication of PSMs in cultivated crops;
Diversity of PSMs in primitive, wild, and cultivated plants.

Dr. Muhammad Junaid Rao
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metabolites is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

secondary metabolites
transcriptional regulation
polyphenols
antioxidant activities
abiotic and biotic stress
nutritional value

Published Papers (5 papers)

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Research

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15 pages, 2745 KiB

Open AccessArticle

Cobalt and Titanium Alleviate the Methylglyoxal-Induced Oxidative Stress in Pennisetum divisum Seedlings under Saline Conditions

by Bushra Ahmed Alhammad, Khansa Saleem, Muhammad Ahsan Asghar, Ali Raza, Abd Ullah, Taimoor Hassan Farooq, Jean W. H. Yong, Fei Xu, Mahmoud F. Seleiman and Aamir Riaz

Metabolites 2023, 13(11), 1162; https://doi.org/10.3390/metabo13111162 - 19 Nov 2023

Viewed by 1208

Abstract

Salinity is considered to be a global problem and a severe danger to modern agriculture since it negatively impacts plants’ growth and development at both cellular- and whole-plant level. However, cobalt (Co) and titanium (Ti), multifunctional non-essential micro-elements, play a crucial role in improving plant growth and development under salinity stress. In the current study, Co and Ti impact on the morphological, biochemical, nutritional, and metabolic profile of Pennisetum divisum plants under three salinity levels which were assessed. Two concentrations of Co (Co-1; 15.0 mg/L and Co-2; 25.0 mg/L), and two concentrations of Ti (Ti-1; 50.0 mg/L and Ti-2; 100.0 mg/L) were applied as foliar application to the P. divisum plants under salinity (S1; 200 mM, S2; 500 mM, and S3; 1000 mM) stress. The results revealed that various morphological, biochemical, and metabolic processes were drastically impacted by the salinity-induced methylglyoxal (MG) stress. The excessive accumulation of salt ions, including Na⁺ (1.24- and 1.21-fold), and Cl⁻ (1.53- and 1.15-fold) in leaves and roots of P. divisum, resulted in the higher production of MG (2.77- and 2.95-fold) in leaves and roots under severe (1000 mM) salinity stress, respectively. However, Ti-treated leaves showed a significant reduction in ionic imbalance and MG concentrations, whereas considerable improvement was shown in K⁺ and Ca²⁺ under salinity stress, and Co treatment showed downregulation of MG content (26, 16, and 14%) and improved the antioxidant activity, such as a reduction in glutathione (GSH), oxidized glutathione (GSSG), Glutathione reductase (GR), Glyoxalase I (Gly I), and Glyoxalase II (Gly II) by up to 1.13-, 1.35-, 3.75-, 2.08-, and 1.68-fold under severe salinity stress in P. divisum roots. Furthermore, MG-induced stress negatively impacted the metabolic profile and antioxidants activity of P. divisum’s root and leaves; however, Co and Ti treatment considerably improved the biochemical processes and metabolic profile in both underground and aerial parts of the studied plants. Collectively, the results depicted that Co treatment showed significant results in roots and Ti treatment presented considerable changes in leaves of P. divism under salinity stress. Full article

(This article belongs to the Special Issue Plant Secondary Metabolites Biosynthesis, Biological Activities and Transcriptional Regulation in Response to Abiotic/Biotic Stresses)

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26 pages, 6543 KiB

Open AccessArticle

Elicitor-Driven Defense Mechanisms: Shielding Cotton Plants against the Onslaught of Cotton Leaf Curl Multan Virus (CLCuMuV) Disease

by Muhammad Fahad Khan, Ummad Ud Din Umar, Abdulwahed Fahad Alrefaei and Muhammad Junaid Rao

Metabolites 2023, 13(11), 1148; https://doi.org/10.3390/metabo13111148 - 12 Nov 2023

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Abstract

Salicylic acid (SA), benzothiadiazole (BTH), and methyl jasmonate (MeJA) are potential elicitors found in plants, playing a crucial role against various biotic and abiotic stresses. The systemic acquired resistance (SAR) mechanism was evaluated in cotton plants for the suppression of Cotton leaf curl Multan Virus (CLCuMuV) by the exogenous application of different elicitors. Seven different treatments of SA, MeJA, and BTH were applied exogenously at different concentrations and combinations. In response to elicitors treatment, enzymatic activities such as SOD, POD, CAT, PPO, PAL, β–1,3 glucanse, and chitinase as biochemical markers for resistance were determined from virus-inoculated and uninoculated cotton plants of susceptible and tolerant varieties, respectively. CLCuMuV was inoculated on cotton plants by whitefly (Bemesia tabaci biotype Asia II-1) and detected by PCR using specific primers for the coat protein region and the Cotton leaf curl betasatellite (CLCuMuBV)-associated component of CLCuMuV. The development of disease symptoms was observed and recorded on treated and control plants. The results revealed that BTH applied at a concentration of 1.1 mM appeared to be the most effective treatment for suppressing CLCuMuV disease in both varieties. The enzymatic activities in both varieties were not significantly different, and the disease was almost equally suppressed in BTH-treated cotton plants following virus inoculation. The beta satellite and coat protein regions of CLCuMuV were not detected by PCR in the cotton plants treated with BTH at either concentration. Among all elicitors, 1.1 mM BTH was proven to be the best option for inducing resistance after the onset of CLCuMuV infection and hence it could be part of the integrated disease management program against Cotton leaf curl virus. Full article

(This article belongs to the Special Issue Plant Secondary Metabolites Biosynthesis, Biological Activities and Transcriptional Regulation in Response to Abiotic/Biotic Stresses)

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21 pages, 6497 KiB

Open AccessArticle

Exogenous TiO₂ Nanoparticles Alleviate Cd Toxicity by Reducing Cd Uptake and Regulating Plant Physiological Activity and Antioxidant Defense Systems in Rice (Oryza sativa L.)

by Anas Iqbal, Zhaowen Mo, Sheng-Gang Pan, Jian-Ying Qi, Tian Hua, Muhammad Imran, Meiyang Duan, Qichang Gu, Xiang-Bin Yao and Xiangru Tang

Metabolites 2023, 13(6), 765; https://doi.org/10.3390/metabo13060765 - 19 Jun 2023

Cited by 1 | Viewed by 1286

Abstract

Cadmium (Cd) is a potentially hazardous element with significant biological toxicity, negatively affecting plant growth and physio-biochemical metabolism. Thus, it is necessary to examine practical and eco-friendly approaches to reduce Cd toxicity. Titanium dioxide nanoparticles (TiO₂-NPs) are growth regulators that help in nutrient uptake and improve plant defense systems against abiotic and biological stress. A pot experiment was performed in the late rice-growing season (July—November) 2022 to explore the role of TiO₂-NPs in relieving Cd toxicity on leaf physiological activity, biochemical attributes, and plant antioxidant defense systems of two different fragrant rice cultivars, i.e., Xiangyaxiangzhan (XGZ) and Meixiangzhan-2 (MXZ-2). Both cultivars were cultivated under normal and Cd-stress conditions. Different doses of TiO₂-NPs with and without Cd-stress conditions were studied. The treatment combinations were: Cd−, 0 mg/kg CdCl₂·2.5 H₂O; Cd+, 50 mg/kg CdCl₂·2.5 H₂O; Cd + NP1, 50 mg/kg Cd + 50 TiO₂-NPs mg/L; Cd + NP2, 50 mg/kg Cd + 100 TiO₂-NPs mg/L; Cd + NP3, 50 mg/kg Cd + 200 TiO₂-NPs mg/L; Cd + NP4, 50 mg/kg Cd + 400 TiO₂-NPs mg/L. Our results showed that the Cd stress significantly (p < 0.05) decreased leaf photosynthetic efficiency, stomatal traits, antioxidant enzyme activities, and the expression of their encoding genes and protein content. Moreover, Cd toxicity destabilized plant metabolism owing to greater accretion of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels at vegetative and reproductive stages. However, TiO₂-NPs application improved leaf photosynthetic efficacy, stomatal traits, and protein and antioxidant enzyme activities under Cd toxicity. Application of TiO₂-NPs decreased the uptake and accumulation of Cd in plants and levels of H₂O₂ and MDA, thereby helping to relieve Cd-induced peroxidation damage of leaf membrane lipids by enhancing the activities of different enzymes like ascorbate peroxidase (APX), catalase (CAT), peroxidase (POS), and superoxide dismutase (SOD). Average increases in SOD, APX, CAT, and POS activities of 120.5 and 110.4%, 116.2 and 123.4%, 41.4 and 43.8%, and 36.6 and 34.2% in MXZ-2 and XGZ, respectively, were noted in Cd + NP3 treatment across the growth stages as compared with Cd-stressed plants without NPs. Moreover, the correlation analysis revealed that the leaf net photosynthetic rate is strongly associated with leaf proline and soluble protein content, suggesting that a higher net photosynthetic rate results in higher leaf proline and soluble protein content. Of the treatments, the Cd + NP3 (50 mg/kg Cd + 200 mg/L TiO₂-NPs) performed the best for both fragrant rice cultivars under Cd toxicity. Our results showed that TiO₂-NPs strengthened rice metabolism through an enhanced antioxidant defense system across the growth stages, thereby improving plant physiological activity and biochemical characteristics under Cd toxicity. Full article

(This article belongs to the Special Issue Plant Secondary Metabolites Biosynthesis, Biological Activities and Transcriptional Regulation in Response to Abiotic/Biotic Stresses)

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20 pages, 3969 KiB

Open AccessArticle

Biochar-Mediated Control of Metabolites and Other Physiological Responses in Water-Stressed Leptocohloa fusca

by Khansa Saleem, Muhammad Ahsan Asghar, Ali Raza, Hafiz Hassan Javed, Taimoor Hassan Farooq, Muhammad Arslan Ahmad, Altafur Rahman, Abd Ullah, Baiquan Song, Junbo Du, Fei Xu, Aamir Riaz and Jean W. H. Yong

Metabolites 2023, 13(4), 511; https://doi.org/10.3390/metabo13040511 - 01 Apr 2023

Cited by 6 | Viewed by 1721

Abstract

We investigated biochar-induced drought tolerance in Leptocohloa fusca (Kallar grass) by exploring the plant defense system at physiological level. L. fusca plants were exposed to drought stress (100%, 70%, and 30% field capacity), and biochar (BC), as an organic soil amendment was applied in two concentrations (15 and 30 mg kg⁻¹ soil) to induce drought tolerance. Our results demonstrated that drought restricted the growth of L. fusca by inhibiting shoot and root (fresh and dry) weight, total chlorophyll content and photosynthetic rate. Under drought stress, the uptake of essential nutrients was also limited due to lower water supply, which ultimately affected metabolites including amino and organic acids, and soluble sugars. In addition, drought stress induced oxidative stress, which is evidenced by the higher production of reactive oxygen species (ROS) including hydrogen peroxide (H₂O₂), superoxide ion (O₂⁻), hydroxyl ion (OH⁻), and malondialdehyde (MDA). The current study revealed that stress-induced oxidative injury is not a linear path, since the excessive production of lipid peroxidation led to the accumulation of methylglyoxal (MG), a member of reactive carbonyl species (RCS), which ultimately caused cell injury. As a consequence of oxidative-stress induction, the ascorbate–glutathione (AsA–GSH) pathway, followed by a series of reactions, was activated by the plants to reduce ROS-induced oxidative damage. Furthermore, biochar considerably improved plant growth and development by mediating metabolites and soil physio-chemical status. Full article

(This article belongs to the Special Issue Plant Secondary Metabolites Biosynthesis, Biological Activities and Transcriptional Regulation in Response to Abiotic/Biotic Stresses)

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Review

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37 pages, 1198 KiB

Open AccessReview

Plant Secondary Metabolites: The Weapons for Biotic Stress Management

by Jameel M. Al-Khayri, Ramakrishnan Rashmi, Varsha Toppo, Pranjali Bajrang Chole, Akshatha Banadka, Wudali Narasimha Sudheer, Praveen Nagella, Wael Fathi Shehata, Muneera Qassim Al-Mssallem, Fatima Mohammed Alessa, Mustafa Ibrahim Almaghasla and Adel Abdel-Sabour Rezk

Metabolites 2023, 13(6), 716; https://doi.org/10.3390/metabo13060716 - 31 May 2023

Cited by 22 | Viewed by 4139

Abstract

The rise in global temperature also favors the multiplication of pests and pathogens, which calls into question global food security. Plants have developed special coping mechanisms since they are sessile and lack an immune system. These mechanisms use a variety of secondary metabolites as weapons to avoid obstacles, adapt to their changing environment, and survive in less-than-ideal circumstances. Plant secondary metabolites include phenolic compounds, alkaloids, glycosides, and terpenoids, which are stored in specialized structures such as latex, trichomes, resin ducts, etc. Secondary metabolites help the plants to be safe from biotic stressors, either by repelling them or attracting their enemies, or exerting toxic effects on them. Modern omics technologies enable the elucidation of the structural and functional properties of these metabolites along with their biosynthesis. A better understanding of the enzymatic regulations and molecular mechanisms aids in the exploitation of secondary metabolites in modern pest management approaches such as biopesticides and integrated pest management. The current review provides an overview of the major plant secondary metabolites that play significant roles in enhancing biotic stress tolerance. It examines their involvement in both indirect and direct defense mechanisms, as well as their storage within plant tissues. Additionally, this review explores the importance of metabolomics approaches in elucidating the significance of secondary metabolites in biotic stress tolerance. The application of metabolic engineering in breeding for biotic stress resistance is discussed, along with the exploitation of secondary metabolites for sustainable pest management. Full article

(This article belongs to the Special Issue Plant Secondary Metabolites Biosynthesis, Biological Activities and Transcriptional Regulation in Response to Abiotic/Biotic Stresses)

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