The vigor and responsiveness of plants to environmental stress result from the constant re-adjustment of physiology and metabolism throughout the life cycle within the framework of the genetic background. Plants have developed unique strategies for responding to ever-changing environmental conditions, exhaustively monitoring their surroundings and adjusting their metabolic systems to maintain homeostasis. The severity of stress, the genetic background of the plant, and its individual history determine everyday survival or death. These factors dictate the destiny of any individual. The genomeenvironment interaction is, therefore, an essential focus for the elucidation of the nature of the phenotypic variation leading to the successful response of plants to environmental cues. Plants acclimate to biotic and abiotic stresses by triggering a cascade or network of events that starts with stress perception and ends with the expression of a battery of target genes. The key components of the stress-response relationship are illustrated in Fig. 1. These are stress stimulus, signals, transducers, transcription regulators, target genes, and stress responses, including morphological, biochemical, and physiological changes. In evolutionary terms, components that are near to the end of the stressresponse cascade are not predicted to be the ones whose actions significantly affect the operation of other genes. However, factors that act at early stages are critical for other cell functions. Plants make use of common pathways and components in the stressresponse relationship. This phenomenon, which is known as cross-tolerance, allows plants to adapt/ acclimate to a range of different stresses after exposure to one specific stress. The major focus of this review, therefore, concerns the basic features of signaling that underpin cross-tolerance and result from the action of common elements, which are likely to occur early in the stress response cascade. First, using drought and chilling as examples, we explore the evidence for common signals and elements that confer cross-tolerance. Second, we highlight the importance of “redox signals” in such networks and discuss the evidence to date for the existence of such pathways in plants. The elucidation of common components has enormous potential and has, therefore, become a priority in research and breeding programs aimed at improving plant stress tolerance.

https://bioinformatics.cs.vt.edu/~easychair/PastoriFoyer_PlantPhys_2002.pdf

Common Components, Networks, and Pathways of Cross-Tolerance to Stress. The Central Role of “Redox” and Abscisic Acid-Mediated Controls

Small heat shock proteins and stress tolerance in plants.

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Abramoff MD, Magalhaes PJ, Ram SJ. 2004. Image Processing with ImageJ. Biophotonics

Plants often face the challenge of severe environmental conditions, which include various biotic and abiotic stresses that exert adverse effects on plant growth and development. During evolution, plants have evolved complex regulatory mechanisms to adapt to various environmental stressors. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species (ROS), which are subsequently converted to hydrogen peroxide (H(2)O(2)). Even under normal conditions, higher plants produce ROS during metabolic processes. Excess concentrations of ROS result in oxidative damage to or the apoptotic death of cells. Development of an antioxidant defense system in plants protects them against oxidative stress damage. These ROS and, more particularly, H(2)O(2,) play versatile roles in normal plant physiological processes and in resistance to stresses. Recently, H(2)O(2) has been regarded as a signaling molecule and regulator of the expression of some genes in cells. This review describes various aspects of H(2)O(2) function, generation and scavenging, gene regulation and cross-links with other physiological molecules during plant growth, development and resistance responses.

Hydrogen peroxide in plants: a versatile molecule of the reactive oxygen species network.

Pharmaceutically significant secondary metabolites or phytopharmaceuticals include alkaloids, glycosides, flavonoids, volatile oils, tannins, resins etc. Currently, most of these secondary metabolites are isolated from wild or cultivated plants because their chemical synthesis is either extremely difficult or economically infeasible. Biotechnological production in plant cell cultures is an attractive alternative, but to date this has had only limited commercial success because of a lack of understanding of how these metabolites are synthesized. Plants and/or plant cells in vitro, show physiological and morphological responses to microbial, physical or chemical factors which are known as ‘elicitors’. Elicitation is a process of induced or enhanced synthesis of secondary metabolites by the plants to ensure their survival, persistence and competitiveness. Here, we discuss the classification of elicitors, their mechanism of action, and applications for the production of phyto-pharmaceuticals from medicinal plants.

Plant cell elicitation for production of secondary metabolites: A review

A protocol is described for rapid RNA isolation from various plant species and tissues rich in polyphenolics and polysaccharides. The method is based on the Nucleon PhytoPure™ system without the use of phenol. The procedure can be completed within 1 h and many samples can be processed at the same time. The yield ranged from 240 μg up to 3 mg per gram of tissue with an average purity measured as A260/280 of 1.85. The RNA was of sufficient quality for use in RT-PCR reactions. Quantitation of single-stranded cDNA was carried out with the RiboGreen™ reagent and of PCR products with the PicoGreen™ reagent.

A simple and efficient protocol for isolation of functional RNA from plant tissues rich in secondary metabolites

Parsley (Petroselinum crispum L.) is known to respond to pathogen attack by the synthesis of furanocoumarins and to UV irradiation by the synthesis of flavone glycosides whereas ozone treatment results in the induction of both pathways. A cDNA library from parsley plants was differentially screened using labelled reverse-transcribed poly(A)+ RNA isolated from ozone-treated parsley plants. This resulted in the isolation of 13 independent cDNA clones representing ozone-induced genes and of 11 cDNA clones representing ozone-repressed genes. DNA sequencing of several clones resulted in the identification of pathogenesis-related protein 1-3 (PR1-3), of a new member of PR1 cDNAs (PR1-4) and of a small heat shock protein (sHSP). Northern blot analyses showed a transient induction of the three mRNA species after ozone fumigation. In contrast, heat shock treatment of parsley plants resulted in an increase of sHSP mRNA whereas no increase for transcripts of PR1-3 and PR1-4 could be observed. This is the first characterized sHSP cDNA clone for plants induced by heat shock, as well as by oxidative stress caused by ozone.

Differential transcript induction of parsley pathogenesis-related proteins and of a small heat shock protein by ozone and heat shock

Nitric oxide burst and nitric oxide-dependent gene induction in plants

This new and simple method of DNA extraction from composite soil allows the isolation of plant DNA with high efficiency, quality and reproductivity. The method is based on a simple CaCl2-precipitation step and requires no additional purification steps to eliminate humic acids. The extracted DNA was obtained in sufficient purity and quantity to allow direct detection of transgenes by PCR. Furthermore, the simple procedure allows the assay of many samples at the same time.

A simple method of DNA extraction from soil for detection of composite transgenic plants by PCR

Changes in the patterns of gene expression were analyzed in ultraviolet-B (UV-B; 280–320 nm) -treated seedlings of European beech by differential display reverse transcriptase polymerase chain reaction (DDRT-PCR) of mRNA. Utilizing 12 different downstream primers and 27 degenerated 10-mer upstream primers 50 induced and 29 repressed cDNA bands were detected. Nineteen bands were subcloned and sequenced. Two clones revealed significant homologies to known database sequences: putative nascent polypeptide-associated complex alpha and 60S ribosomal protein L37. However, only the latter was confirmed to be UV-B-induced by northern blot analysis.

Evi Kiefer

Papers

A simple and efficient protocol for isolation of functional RNA from plant tissues rich in secondary metabolites

Differential transcript induction of parsley pathogenesis-related proteins and of a small heat shock protein by ozone and heat shock

Nitric oxide burst and nitric oxide-dependent gene induction in plants

A simple method of DNA extraction from soil for detection of composite transgenic plants by PCR

Early changes in mRNA populations in leaves of ultraviolet-B-treated European beech ( Fagus sylvatica L.) seedlings