Identification and Functional Characterization of Plant Toxins (original) (raw)
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Toxins are naturally present in a wide variety of plants. Plants evolve to generate natural products as a means of defence against animals. Phytotoxins have been reported for many useful effects. Some plants produce toxins that can severely harm or destroy any herbivore. They can be modified to exemplify improved affinity and efficacy for health endorsement. Several of these plants are commonly consumed as food. They have been developed as an evolutionary movement for self-protection. These toxic substances when taken in considerable amount can be harmful to human health and cause problems. This review gives an outline on different plant toxins, their mechanism of action and different toxicological effects due to plant toxins.
Plant toxins-useful and harmful effects
Plan: To review the useful and harmful effects of plant toxins. Prologue: Poisonous chemicals found in plants are normal biochemicals. They have been developed as an evolutionary response for self-protection. Therefore, plants are deliberately poisonous and their toxicity to humans and other animals is an example of natural selection.. The surviving plants, therefore, have not been subjected to selective pressures which might influence them to produce toxins. The alkaloids are by far the most predominant of plant toxins and because of their enormous structural diversity and various modes of action, examples may be chosen from among them to serve as paradigms for virtually every type of plant-herbivore interaction. Outcome: Since plant toxins show many useful effects they can be used in treating respective diseases. They can be modified to show better affinity and efficacy. Regardless of the structure of a particular toxin, it is likely to have evolved and been elaborated biosyntheti...
Troublesome toxins time to re-think plant-herbivore interactions in vertebrate ecology
Earlier models of plant-herbivore interactions relied on forms of functional response that related rates of ingestion by herbivores to mechanical or physical attributes such as bite size and rate. These models fail to predict a growing number of findings that implicate chemical toxins as important determinants of plant-herbivore dynamics. Specifically, considerable evidence suggests that toxins set upper limits on food intake for many species of herbivorous vertebrates. Herbivores feeding on toxin-containing plants must avoid saturating their detoxification systems, which often occurs before ingestion rates are limited by mechanical handling of food items. In light of the importance of plant toxins, a new approach is needed to link herbivores to their food base. We discuss necessary features of such an approach, note recent advances in herbivore functional response models that incorporate effects of plant toxins, and mention predictions that are consistent with observations in natural systems. Future ecological studies will need to address explicitly the importance of plant toxins in shaping plant and herbivore communities.
Mode of action and toxicology of plant toxins and poisonous plants
TOXICOLOGY (1), 2022
Plants have evolved the strategy to produce bioactive natural products as a means of defence against herbivores and microbes. Some plants produce toxins that can severely damage or kill a herbivore. The molecular mode of action of neurotoxins, cytotoxins, metabolic poisons, mutagens and toxins that affect skin and mucosal tissues are summarised and discussed. Important poisonous plants of Europe, their toxins and toxicology are tabulated, as this group of plants can provide lead compounds for the development of natural pesticides against insects, slugs or rodents.
Plant Insecticidal Toxins in Ecological Networks
Toxins, 2012
Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C-or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects' vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology.
A common toxin fold mediates microbial attack and plant defense
Proceedings of the National Academy of Sciences, 2009
Many plant pathogens secrete toxins that enhance microbial virulence by killing host cells. Usually, these toxins are produced by particular microbial taxa, such as bacteria or fungi. In contrast, many bacterial, fungal and oomycete species produce necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) that trigger leaf necrosis and immunity-associated responses in various plants. We have determined the crystal structure of an NLP from the phytopathogenic oomycete Pythium aphanidermatum to 1.35Å resolution. The protein fold exhibits structural similarities to cytolytic toxins produced by marine organisms (actinoporins). Computational modeling of the 3-dimensional structure of NLPs from another oomycete, Phytophthora parasitica, and from the phytopathogenic bacterium, Pectobacterium carotovorum, revealed a high extent of fold conservation. Expression of the 2 oomycete NLPs in an nlp-deficient P. carotovorum strain restored bacterial virulence, suggesting that NLPs of prokaryotic and eukaryotic origins are orthologous proteins. NLP mutant protein analyses revealed that identical structural properties were required to cause plasma membrane permeabilization and cytolysis in plant cells, as well as to restore bacterial virulence. In sum, NLPs are conserved virulence factors whose taxonomic distribution is exceptional for microbial phytotoxins, and that contribute to host infection by plasma membrane destruction and cytolysis. We further show that NLP-mediated phytotoxicity and plant defense gene expression share identical fold requirements, suggesting that toxin-mediated interference with host integrity triggers plant immunity-associated responses. Phytotoxin-induced cellular damage-associated activation of plant defenses is reminiscent of microbial toxin-induced inflammasome activation in vertebrates and may thus constitute another conserved element in animal and plant innate immunity.
Natural Toxins in Plant Foodstuffs
Since food plants are mixtures of large numbers of chemical compounds and since any substance is toxic in a high enough dose, it is not suprising that natural food plants are toxic under certain conditions. Toxicity from common natural foods has resulted from long-term consumption of a single food item or from short periods of consumption of foods con taining unusually high levels of a toxic substance. The process of diet selection has been continuous since prehistory and has minimized con sumption of foods of high toxicity.
2018
Naturally, plant habitats are exposed to several potential effects of biotic and different abiotic environmental challenges. Several types of micro-organisms namely; bacteria, viruses, fungi, nematodes, mites, insects, mammals and other herbivorous animals are found in large amounts in all ecosystems, which lead to considerable reduction in crop productivity. These organisms are agents carrying different diseases that can damage the plants through the secretion of toxic-microbial poisons that can penetrate in the plant tissues. Toxins are injurious substances that act on plant protoplast to influence disease development. In response to the stress effect, plants defend themselves by bearing some substances such as phytoalexins. Production of phytoalexins is one of the complex mechanisms through which plants exhibit disease resistance. Several findings specifically on phytoalexins have widen the understanding in the fields of plant biochemistry and molecular biology. However, this rev...
The Influence of Toxins in Disease Symptom Initiation in Plants: A Review
Journal of Agriculture and Sustainability, 2017
The concept that plant pathogens cause disease by producing toxic substances dates back about a century. Evidence for its general validity, however, has accumulated only recently. The difficulty has been that most plant disease symptoms are the result of a complex interplay of several factors. Some pathogens, in addition to producing one or more toxins, may also excrete enzymes which degrade cell walls, causing tissue disorganization; they may destroy plant hormones, causing abnormal growth of the host; or they may physically block the water-conducting vessels of the host by their prolific growth or by production of viscous polysaccharides. Because of this complexity, proof of the role of a toxin as one of several interacting factors causing a disease symptom is often difficult to obtain, even though the presence of toxic substances in cultures of most plant pathogens is easily demonstrated. Despite these problems, our growing knowledge of the biochemistry of symptom causation clearly establishes the role of toxins as a dominant one in most plant diseases.