Heavy metal stress and mitogen activated kinase transcription factors in plants: Exploring heavy metal-ROS influences on plant signalling pathways.

Due to their stationary nature, plants are exposed to a diverse range of biotic and abiotic stresses, of which heavy metal (HM) stress poses one of the most detrimental abiotic stresses, targeting diverse plant processes. HMs instigate the overproduction of reactive oxygen species (ROS), and to mitigate the adverse effects of ROS, plants induce multiple defence mechanisms. Besides the negative implications of overproduction of ROS, these molecules play a multitude of signalling roles in plants, acting as a central player in the complex signalling network of cells. One of the ROS-associated signalling mechanisms is the mitogen-activated protein kinase (MAPK) cascade, a signalling pathway which transduces extracellular stimuli into intracellular responses. Plant MAPKs have been implicated in signalling involved in stress response, phytohormone regulation, and cell cycle cues. However, the influence of various HMs on MAPK activation has not been well documented. In this review, we address and summarise several aspects related to various HM-induced ROS signalling. Additionally, we touch on how these signals activate the MAPK cascade and the downstream transcription factors that influence plant responses to HMs. Moreover, we propose a workflow that could characterise genes associated with MAPKs and their roles during plant HM stress responses.

Methylglyoxal improves zirconium stress tolerance in Raphanus sativus seedling shoots by restricting zirconium uptake, reducing oxidative damage, and upregulating glyoxalase I.

Raphanus sativus also known as radish is a member of the Brassicaceae family which is mainly cultivated for human and animal consumption. R. sativus growth and development is negatively affected by heavy metal stress. The metal zirconium (Zr) have toxic effects on plants and tolerance to the metal could be regulated by known signaling molecules such as methylglyoxal (MG). Therefore, in this study we investigated whether the application of the signaling molecule MG could improve the Zr tolerance of R. sativus at the seedling stage. We measured the following: seed germination, dry weight, cotyledon abscission (%), cell viability, chlorophyll content, malondialdehyde (MDA) content, conjugated diene (CD) content, hydrogen peroxide (H2O2) content, superoxide (O2•-) content, MG content, hydroxyl radical (·OH) concentration, ascorbate peroxidase (APX) activity, superoxide dismutase (SOD) activity, glyoxalase I (Gly I) activity, Zr content and translocation factor. Under Zr stress, exogenous MG increased the seed germination percentage, shoot dry weight, cotyledon abscission, cell viability and chlorophyll content. Exogenous MG also led to a decrease in MDA, CD, H2O2, O2•-, MG and ·OH, under Zr stress in the shoots. Furthermore, MG application led to an increase in the enzymatic activities of APX, SOD and Gly I as well as in the complete blocking of cotyledon abscission under Zr stress. MG treatment decreased the uptake of Zr in the roots and shoots. Zr treatment decreased the translocation factor of the Zr from roots to shoots and MG treatment decreased the translocation factor of Zr even more significantly compared to the Zr only treatment. Our results indicate that MG treatment can improve R. sativus seedling growth under Zr stress through the activation of antioxidant enzymes and Gly I through reactive oxygen species and MG signaling, inhibiting cotyledon abscission through H2O2 signaling and immobilizing Zr translocation.

Recent Progress in the Characterization, Synthesis, Delivery Procedures, Treatment Strategies, and Precision of Antimicrobial Peptides.

Infectious diseases are constantly evolving to bypass antibiotics or create resistance against them. There is a piercing alarm for the need to improve the design of new effective antimicrobial agents such as antimicrobial peptides which are less prone to resistance and possess high sensitivity. This would guard public health in combating and overcoming stubborn pathogens and mitigate incurable diseases; however, the emergence of antimicrobial peptides' shortcomings ranging from untimely degradation by enzymes to difficulty in the design against specific targets is a major bottleneck in achieving these objectives. This review is aimed at highlighting the recent progress in antimicrobial peptide development in the area of nanotechnology-based delivery, selectivity indices, synthesis and characterization, their doping and coating, and the shortfall of these approaches. This review will raise awareness of antimicrobial peptides as prospective therapeutic agents in the medical and pharmaceutical industries, such as the sensitive treatment of diseases and their utilization. The knowledge from this development would guide the future design of these novel peptides and allow the development of highly specific, sensitive, and accurate antimicrobial peptides to initiate treatment regimens in patients to enable them to have accommodating lifestyles.

Biocontrol Potential of Bacillus subtilis and Bacillus tequilensis against Four Fusarium Species.

The use of biological control agents as opposed to synthetic agrochemicals to control plant pathogens has gained momentum, considering their numerous advantages. The aim of this study is to investigate the biocontrol potential of plant bacterial isolates against Fusarium oxysporum, Fusarium proliferatum, Fusarium culmorum, and Fusarium verticillioides. Isolation, identification, characterization, and in vitro biocontrol antagonistic assays of these isolates against Fusarium species were carried out following standard protocols. The bacterial endophytes were isolated from Glycine max. L leaves (B1), Brassica napus. L seeds (B2), Vigna unguiculata seeds (B3), and Glycine max. L seeds (B4). The bacterial isolates were identified using 16S rRNA PCR sequencing. A phylogenetic analysis shows that the bacterial isolates are closely related to Bacillus subtilis (B1) and Bacillus tequilensis (B2-B4), with an identity score above 98%. All the bacterial isolates produced a significant amount (p < 0.05) of indole acetic acid (IAA), siderophores, and protease activity. In vitro antagonistic assays of these isolates show a significant (p < 0.05) growth inhibition of the fungal mycelia in the following order: F. proliferatum > F. culmorum > F. verticillioides > F. oxysporum, compared to the control. The results suggest that these bacterial isolates are good biocontrol candidates against the selected Fusarium species.

Insights into the Effects of Hydroxycinnamic Acid and Its Secondary Metabolites as Antioxidants for Oxidative Stress and Plant Growth under Environmental Stresses.

Plant immobility renders plants constantly susceptible to various abiotic and biotic stresses. Abiotic and biotic stresses are known to produce reactive oxygen species (ROS), which cause comparable cellular secondary reactions (osmotic or oxidative stress), leading to agricultural productivity constraints worldwide. To mitigate the challenges caused by these stresses, plants have evolved a variety of adaptive strategies. Phenolic acids form a key component of these strategies, as they are predominantly known to be secreted by plants in response to abiotic or biotic stresses. Phenolic acids can be divided into different subclasses based on their chemical structures, such as hydroxybenzoic acids and hydroxycinnamic acids. This review analyzes hydroxycinnamic acids and their derivatives as they increase under stressful conditions, so to withstand environmental stresses they regulate physiological processes through acting as signaling molecules that regulate gene expression and biochemical pathways. The mechanism of action used by hydroxycinnamic acid involves minimization of oxidative damage to maintain cellular homeostasis and protect vital cellular components from harm. The purpose of this review is to highlight the potential of hydroxycinnamic acid metabolites/derivatives as potential antioxidants. We review the uses of different secondary metabolites associated with hydroxycinnamic acid and their contributions to plant growth and development.

Draft Whole-Genome Sequence of Penicillium simplicissimum A4, a Putative Endophyte from Echium plantagineum.

We report the draft whole-genome sequence of the putative endophytic fungus Penicillium simplicissimum A4, isolated from the roots of Echium plantagineum plants. The genome was sequenced using PacBio technology with an estimated genome size of 39 Mb.

In silico discovery of biomarkers for the accurate and sensitive detection of Fusarium solani.

Fusarium solani is worrisome because it severely threatens the agricultural productivity of certain crops such as tomatoes and peas, causing the general decline, wilting, and root necrosis. It has also been implicated in the infection of the human eye cornea. It is believed that early detection of the fungus could save these crops from the destructive activities of the fungus through early biocontrol measures. Therefore, the present work aimed to build a sensitive model of novel anti-Fusarium solani antimicrobial peptides (AMPs) against the fungal cutinase 1 (CUT1) protein for early, sensitive and accurate detection. Fusarium solani CUT1 receptor protein 2D secondary structure, model validation, and functional motifs were predicted. Subsequently, anti-Fusarium solani AMPs were retrieved, and the HMMER in silico algorithm was used to construct a model of the AMPs. After their structure predictions, the interaction analysis was analyzed for the Fusarium solani CUT1 protein and the generated AMPs. The putative anti-Fusarium solani AMPs bound the CUT1 protein very tightly, with OOB4 having the highest binding energy potential for HDock. The pyDockWeb generated high electrostatic, desolvation, and low van der Waals energies for all the AMPs against CUT1 protein, with OOB1 having the most significant interaction. The results suggested the utilization of AMPs for the timely intervention, control, and management of these crops, as mentioned earlier, to improve their agricultural productivity and reduce their economic loss and the use of HMMER for constructing models for disease detection.

Seaweed-Derived Phenolic Compounds in Growth Promotion and Stress Alleviation in Plants.

Abiotic and biotic stress factors negatively influence the growth, yield, and nutritional value of economically important food and feed crops. These climate-change-induced stress factors, together with the ever-growing human population, compromise sustainable food security for all consumers across the world. Agrochemicals are widely used to increase crop yield by improving plant growth and enhancing their tolerance to stress factors; however, there has been a shift towards natural compounds in recent years due to the detrimental effect associated with these agrochemicals on crops and the ecosystem. In view of these, the use of phenolic biostimulants as opposed to artificial fertilizers has gained significant momentum in crop production. Seaweeds are marine organisms and excellent sources of natural phenolic compounds that are useful for downstream agricultural applications such as promoting plant growth and improving resilience against various stress conditions. In this review, we highlight the different phenolic compounds present in seaweed, compare their extraction methods, and describe their downstream applications in agriculture.

Analytical Studies of Antimicrobial Peptides as Diagnostic Biomarkers for the Detection of Bacterial and Viral Pneumonia.

Pneumonia remains one of the leading causes of infectious mortality and significant economic losses among our growing population. The lack of specific biomarkers for correct and timely diagnosis to detect patients' status is a bane towards initiating a proper treatment plan for the disease; thus, current biomarkers cannot distinguish between pneumonia and other associated conditions such as atherosclerotic plaques and human immunodeficiency virus (HIV). Antimicrobial peptides (AMPs) are potential candidates for detecting numerous illnesses due to their compensatory roles as theranostic molecules. This research sought to generate specific data for parental AMPs to identify viral and bacterial pneumonia pathogens using in silico technology. The parental antimicrobial peptides (AMPs) used in this work were AMPs discovered in our previous in silico analyses using the HMMER algorithm, which were used to generate derivative (mutated) AMPs that would bind with greater affinity, in order to detect the bacterial and viral receptors using an in silico site-directed mutagenesis approach. These AMPs' 3D structures were subsequently predicted and docked against receptor proteins. The result shows putative AMPs with the potential capacity to detect pneumonia caused by these pathogens through their binding precision with high sensitivity, accuracy, and specificity for possible use in point-of-care diagnosis. These peptides' tendency to detect receptor proteins of viral and bacterial pneumonia with precision justifies their use for differential diagnostics, in an attempt to reduce the problems of indiscriminate overuse, toxicity due to the wrong prescription, bacterial resistance, and the scarcity and high cost of existing pneumonia antibiotics.

Piperonylic acid alters growth, mineral content accumulation and reactive oxygen species-scavenging capacity in chia seedlings.

p-Coumaric acid synthesis in plants involves the conversion of phenylalanine to trans-cinnamic acid via phenylalanine ammonia-lyase (PAL), which is then hydroxylated at the para-position under the action of trans-cinnamic acid 4-hydroxylase. Alternatively, some PAL enzymes accept tyrosine as an alternative substrate and convert tyrosine directly to p-coumaric acid without the intermediary of trans-cinnamic acid. In recent years, the contrasting roles of p-coumaric acid in regulating the growth and development of plants have been well-documented. To understand the contribution of trans-cinnamic acid 4-hydroxylase activity in p-coumaric acid-mediated plant growth, mineral content accumulation and the regulation of reactive oxygen species (ROS), we investigated the effect of piperonylic acid (a trans-cinnamic acid 4-hydroxylase inhibitor) on plant growth, essential macroelements, osmolyte content, ROS-induced oxidative damage, antioxidant enzyme activities and phytohormone levels in chia seedlings. Piperonylic acid restricted chia seedling growth by reducing shoot length, fresh weight, leaf area measurements and p-coumaric acid content. Apart from sodium, piperonylic acid significantly reduced the accumulation of other essential macroelements (such as K, P, Ca and Mg) relative to the untreated control. Enhanced proline, superoxide, hydrogen peroxide and malondialdehyde contents were observed. The inhibition of trans-cinnamic acid 4-hydroxylase activity significantly increased the enzymatic activities of ROS-scavenging enzymes such as superoxide dismutase, ascorbate peroxidase, catalase and guaiacol peroxidase. In addition, piperonylic acid caused a reduction in indole-3-acetic acid and salicylic acid content. In conclusion, the reduction in chia seedling growth in response to piperonylic acid may be attributed to a reduction in p-coumaric acid content coupled with elevated ROS-induced oxidative damage, and restricted mineral and phytohormone (indole-3-acetic acid and salicylic) levels.

Biofertilizer: The Future of Food Security and Food Safety.

There is a direct correlation between population growth and food demand. As the global population continues to rise, there is a need to scale up food production to meet the food demand of the population. In addition, the arable land over time has lost its naturally endowed nutrients. Hence, alternative measures such as fertilizers, pesticides, and herbicides are used to fortify the soil and scale up the production rate. As efforts are being made to meet this food demand and ensure food security, it is equally important to ensure food safety for consumption. Food safety measures need to be put in place throughout the food production chain lines. One of the fundamental measures is the use of biofertilizers or plant growth promoters instead of chemical or synthesized fertilizers, pesticides, and herbicides that poise several dangers to human and animal health. Biofertilizers competitively colonize plant root systems, which, in turn, enhance nutrient uptake, increase productivity and crop yield, improve plants' tolerance to stress and their resistance to pathogens, and improve plant growth through mechanisms such as the mobilization of essential elements, nutrients, and plant growth hormones. Biofertilizers are cost-effective and ecofriendly in nature, and their continuous usage enhances soil fertility. They also increase crop yield by up to about 10-40% by increasing protein contents, essential amino acids, and vitamins, and by nitrogen fixation. This review therefore highlighted different types of biofertilizers and the mechanisms by which they elicit their function to enhance crop yield to meet food demand. In addition, the review also addressed the role of microorganisms in promoting plant growth and the various organisms that are beneficial for enhancing plant growth.

Plant Antimicrobial Peptides (PAMPs): Features, Applications, Production, Expression, and Challenges.

The quest for an extraordinary array of defense strategies is imperative to reduce the challenges of microbial attacks on plants and animals. Plant antimicrobial peptides (PAMPs) are a subset of antimicrobial peptides (AMPs). PAMPs elicit defense against microbial attacks and prevent drug resistance of pathogens given their wide spectrum activity, excellent structural stability, and diverse mechanism of action. This review aimed to identify the applications, features, production, expression, and challenges of PAMPs using its structure-activity relationship. The discovery techniques used to identify these peptides were also explored to provide insight into their significance in genomics, transcriptomics, proteomics, and their expression against disease-causing pathogens. This review creates awareness for PAMPs as potential therapeutic agents in the medical and pharmaceutical fields, such as the sensitive treatment of bacterial and fungal diseases and others and their utilization in preserving crops using available transgenic methods in the agronomical field. PAMPs are also safe to handle and are easy to recycle with the use of proteases to convert them into more potent antimicrobial agents for sustainable development.

Cadmium interference with iron sensing reveals transcriptional programs sensitive and insensitive to reactive oxygen species.

Iron (Fe) is an essential micronutrient whose uptake is tightly regulated to prevent either deficiency or toxicity. Cadmium (Cd) is a non-essential element that induces both Fe deficiency and toxicity; however, the mechanisms behind these Fe/Cd-induced responses are still elusive. Here we explored Cd- and Fe-associated responses in wild-type Arabidopsis and in a mutant that overaccumulates Fe (opt3-2). Gene expression profiling revealed a large overlap between transcripts induced by Fe deficiency and Cd exposure. Interestingly, the use of opt3-2 allowed us to identify additional gene clusters originally induced by Cd in the wild type but repressed in the opt3-2 background. Based on the high levels of H2O2 found in opt3-2, we propose a model where reactive oxygen species prevent the induction of genes that are induced in the wild type by either Fe deficiency or Cd. Interestingly, a defined cluster of Fe-responsive genes was found to be insensitive to this negative feedback, suggesting that their induction by Cd is more likely to be the result of an impaired Fe sensing. Overall, our data suggest that Fe deficiency responses are governed by multiple inputs and that a hierarchical regulation of Fe homeostasis prevents the induction of specific networks when Fe and H2O2 levels are elevated.

Biomedical Relevance of Novel Anticancer Peptides in the Sensitive Treatment of Cancer.

The global increase in cancer mortality and economic losses necessitates the cautious quest for therapeutic agents with compensatory advantages over conventional therapies. Anticancer peptides (ACPs) are a subset of host defense peptides, also known as antimicrobial peptides, which have emerged as therapeutic and diagnostic candidates due to several compensatory advantages over the non-specificity of the current treatment regimens. This review aimed to highlight the ravaging incidence of cancer, the use of ACPs in cancer treatment with their mechanisms, ACP discovery and delivery methods, and the limitations for their use. This would create awareness for identifying more ACPs with better specificity, accuracy and sensitivity towards the disease. It would also promote their efficacious utilization in biotechnology, medical sciences and molecular biology to ease the severity of the disease and enable the patients living with these conditions to develop an accommodating lifestyle.

The Relationship between Cadmium Toxicity and the Modulation of Epigenetic Traits in Plants.

Elevated concentrations of heavy metals such as cadmium (Cd) have a negative impact on staple crop production due to their ability to elicit cytotoxic and genotoxic effects on plants. In order to understand the relationship between Cd stress and plants in an effort to improve Cd tolerance, studies have identified genetic mechanisms which could be important for conferring stress tolerance. In recent years epigenetic studies have garnered much attention and hold great potential in both improving the understanding of Cd stress in plants as well as revealing candidate mechanisms for future work. This review describes some of the main epigenetic mechanisms involved in Cd stress responses. We summarize recent literature and data pertaining to chromatin remodeling, DNA methylation, histone acetylation and miRNAs in order to understand the role these epigenetic traits play in cadmium tolerance. The review aims to provide the framework for future studies where these epigenetic traits may be used in plant breeding and molecular studies in order to improve Cd tolerance.

Exogenous 3,3'-Diindolylmethane Improves Vanadium Stress Tolerance in Brassica napus Seedling Shoots by Modulating Antioxidant Enzyme Activities.

3,3'-diindolylmethane (DIM) belongs to a family of indole glucosinolate compounds that have been shown to improve Brassica napus growth through the modulation of reactive oxygen species when applied exogenously. The B. napus cultivar AV Garnet was previously identified as a vanadium-sensitive cultivar. Therefore, in this study we investigated whether exogenous DIM could improve the vanadium tolerance of AV Garnet. We performed the following experiments: seed germination assessment, dry weight assessment, cell viability assay, chlorophyll content assay, malondialdehyde (MDA) assay, conjugated diene (CD) content assay, hydrogen peroxide (H2O2) content assay, superoxide (O2-) content determination, methylglyoxal (MG) content determination, hydroxyl radical (·OH) concentration determination, ascorbate peroxidase (APX) activity assay, superoxide dismutase (SOD) activity assay, glyoxalase I (Gly I) activity assay, glutathione S-transferase (GST) activity assay and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis for vanadium content determination. Under vanadium stress, exogenous DIM increased the seed germination percentage, shoot dry weight, cell viability and chlorophyll content. Exogenous DIM also led to a decrease in MDA, CD, H2O2, O2-, MG and ·OH, under vanadium stress in the shoots. Furthermore, DIM application led to an increase in the enzymatic activities of APX, SOD, Gly I and GST under vanadium stress. Interestingly, under vanadium stress, DIM treatment did not alter vanadium content in B. napus shoots. Our results indicate that exogenous application of DIM can improve B. napus seedling shoot growth and biomass under vanadium stress by priming the antioxidant enzymes via reactive oxygen species (ROS) signaling.

Draft Genome Sequence of the Putative Endophytic Bacterium Pantoea agglomerans R6, Associated with Lactuca serriola from South Africa.

Here, we present the draft genome sequence (∼4.7 Mb) of the endopyhtic bacterium Pantoea agglomerans strain R6, which was isolated from surface-sterilized roots of Lactuca serriola (prickly lettuce).

PR-1-Like Protein as a Potential Target for the Identification of Fusarium oxysporum: An In Silico Approach.

Fusarium oxysporum remains one of the leading causes of economic losses and poor crop yields; its detection is strained due to its presentation in various morphological and physiological forms. This research work sought to identify novel biomarkers for the detection of Fusarium oxysporum using in silico approaches. Experimentally validated anti-Fusarium oxysporum antimicrobial peptides (AMPs) were used to construct a profile against Fusarium oxysporum. The performance and physicochemical parameters of these peptides were predicted. The gene for the Fusarium oxysporum receptor protein PR-1-like Protein, Fpr1, was identified and translated. The resulting protein model from the translation was then validated. The anti-Fusarium oxysporum AMPs and Fusarium oxysporum receptor protein 3-D structures were characterized, and their docking interaction analyses were carried out. The HMMER in silico tool identified novel anti-Fusarium oxysporum antimicrobial peptides with good performance in terms of accuracy, sensitivity, and specificity. These AMPs also displayed good physicochemical properties and bound with greater affinity to Fusarium oxysporum protein receptor PR-1-like Protein. The tendency of these AMPs to precisely detect Fusarium oxysporum PR-1-like Protein, Fpr1, would justify their use for the identification of the fungus. This study would enhance and facilitate the identification of Fusarium oxysporum to reduce problems associated with poor crop yield, economic losses, and decreased nutritional values of plants to keep up with the growing population.

Decoding Heavy Metal Stress Signalling in Plants: Towards Improved Food Security and Safety.

The mining of heavy metals from the environment leads to an increase in soil pollution, leading to the uptake of heavy metals into plant tissue. The build-up of toxic metals in plant cells often leads to cellular damage and senescence. Therefore, it is of utmost importance to produce plants with improved tolerance to heavy metals for food security, as well as to limit heavy metal uptake for improved food safety purposes. To achieve this goal, our understanding of the signaling mechanisms which regulate toxic heavy metal uptake and tolerance in plants requires extensive improvement. In this review, we summarize recent literature and data on heavy metal toxicity (oral reference doses) and the impact of the metals on food safety and food security. Furthermore, we discuss some of the key events (reception, transduction, and response) in the heavy metal signaling cascades in the cell wall, plasma membrane, and cytoplasm. Our future perspectives provide an outlook of the exciting advances that will shape the plant heavy metal signaling field in the near future.

Exogenous p-Coumaric Acid Improves Salvia hispanica L. Seedling Shoot Growth.

: p-Coumaric acid (p-CA) belongs to a family of natural esters of hydroxycinnamic acid compounds that have been shown to modulate plant growth and metabolism. In this study, we investigated the effect of exogenous p-CA on plant growth, reactive oxygen species (ROS)-induced oxidative damage, photosynthetic metabolism, osmolyte content and changes in superoxide dismutase (SOD) enzymatic activity. Exogenous p-CA improved Salvia hispanica (chia) growth by significantly enhancing shoot length, fresh and dry weights coupled with augmented levels of total chlorophyll and carotenoid contents. Furthermore, p-CA also triggered an induction in proline, glycine betaine (GB) and superoxide (O2∙-) levels while no changes were observed for hydrogen peroxide (H2O2) and downstream malondialdehyde (MDA) content. Also, no change in SOD activity was observed in the p-CA treatment relative to the control. Therefore, the results suggest that exogenous p-CA improves chia seedling growth possibly via activation of a ROS-signalling pathway involving O2∙- under the control of proline accumulation.