Biological effects of essential oils - A review

Phenylpropanoid compounds encompass a wide range of structural classes and biological functions. Limiting discussion to stress-induced phenylpropanoids eliminates few of the structural classes, because many compounds thst are constitutive in one plant species or tissue can be induced by various stresses in another species or in another tissue of the same plant (Beggs et al., 1987; Christie et al., 1994).

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Stress-Induced Phenylpropanoid Metabolism.

Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

https://downloads.hindawi.com/archive/2012/217037.pdf

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Roles of glycine betaine and proline in improving plant abiotic stress resistance

Peptidoglycan types of bacterial cell walls and their taxonomic implications.

Since its publication in 2000, Biochemistry & Molecular Biology of Plants, has been hailed as a major contribution to the plant sciences literature and critical acclaim has been matched by global sales success. Maintaining the scope and focus of the first edition, the second will provide a major update, include much new material and reorganise some chapters to further improve the presentation. This book is meticulously organised and richly illustrated, having over 1,000 full-colour illustrations and 500 photographs. It is divided into five parts covering: Compartments: Cell Reproduction: Energy Flow; Metabolic and Developmental Integration; and Plant Environment and Agriculture. Specific changes to this edition include: Completely revised with over half of the chapters having a major rewrite. Includes two new chapters on signal transduction and responses to pathogens. Restructuring of section on cell reproduction for improved presentation. Dedicated website to include all illustrative material. Biochemistry & Molecular Biology of Plants holds a unique place in the plant sciences literature as it provides the only comprehensive, authoritative, integrated single volume book in this essential field of study.

Biochemistry & Molecular Biology of Plants

INTRODUCTION 342 IN VIVO ACTIVATION STUDIES 342 STUDIES WITH INTACT CHLOROPLASTS 344 Light-Dependent Enzyme Activation 344 Effects of Inhibitors 346 Light-Induced Change in Stromal pH 348 Light-Induced Change in Stromal M� Concentration 348 STUDIES WITH ENZYME SYSTEMS 350 Mechanisms of Light Activation 350 Effector-mediated mechanisms 350 lon-mediated mechanisms 353 Protein-mediated mechanisms 353 Mechanisms of Deactivation in the Dark 358 DEVELOPMENTAL ASPECTS 359 ACTIVATION OF MEMBRANOUS ENZYMES 360 OXIDANT·LINKED ACTIVATION 361

Role of Light in the Regulation of Chloroplast Enzymes

Initially discovered in the context of photosynthesis, regulation by change in the redox state of thiol groups (S-S 2SH) is now known to occur throughout biology. Several systems, each linking a hydrogen donor to an intermediary disulfide protein, act to effect changes that alter the activity of target proteins: the ferredoxin/thioredoxin system, comprised of reduced ferredoxin, a thioredoxin, and the enzyme, ferredoxin-thioredoxin reductase; the NADP/thioredoxin system, including NADPH, a thioredoxin, and NADP-thioredoxin reductase; and the glutathione/glutaredoxin system, composed of reduced glutathione and a glutaredoxin. A related disulfide protein, protein disulfide isomerase (PDI) acts in protein assembly. Regulation linked to plastoquinone and signaling induced by reactive oxygen species (ROS) and other agents are also being actively investigated. Progress made on these systems has linked redox to the regulation of an increasing number of processes not only in plants, but in other types of organisms as well. Research in areas currently under exploration promises to provide a fuller understanding of the role redox plays in cellular processes, and to further the application of this knowledge to technology and medicine.

Redox Regulation: A Broadening Horizon

The plant hormone abscisic acid (ABA) serves as a physiological monitor to assess the water status of plants and, under drought conditions, induces stomatal pore closure by activating specific ion channels, such as a slow-anion channel (SLAC1) that, in turn, mediate ion efflux from the guard cells. Earlier genetic analyses uncovered a protein kinase (OST1) and several 2C-type phosphatases, as respective positive and negative regulators of ABA-induced stomatal closure. Here we show that the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. PP2CA, one of the PP2C phosphatase family members acts in an opposing manner and inhibits the activity of SLAC1 by two mechanisms: (1) direct interaction with SLAC1 itself, and (2) physical interaction with OSTI leading to inhibition of the kinase independently of phosphatase activity. The results suggest that ABA signaling is mediated by a physical interaction chain consisting of several components, including a PP2C member, SnRK2-type kinase (OST1), and an ion channel, SLAC1, to regulate stomatal movements. The findings are in keeping with a paradigm in which a protein kinase-phosphatase pair interacts physically with a target protein to couple a signal with a specific response.

https://www.pnas.org/content/pnas/106/50/21419.full.pdf

Bob B. Buchanan

Papers

Biochemistry & Molecular Biology of Plants

Role of Light in the Regulation of Chloroplast Enzymes

Redox Regulation: A Broadening Horizon

A protein kinase-phosphatase pair interacts with an ion channel to regulate ABA signaling in plant guard cells

Studies on the chemical nature of clostridial ferredoxin.