Infrared spectroscopy of proteins.

Antioxidants, Oxidative Damage and Oxygen Deprivation Stress: a Review

In the last decade, our understanding of the processes underlying plant response to drought, at the molecular and whole-plant levels, has rapidly progressed. Here, we review that progress. We draw attention to the perception and signalling processes (chemical and hydraulic) of water deficits. Knowledge of these processes is essential for a holistic understanding of plant resistance to stress, which is needed to improve crop management and breeding techniques. Hundreds of genes that are induced under drought have been identified. A range of tools, from gene expression patterns to the use of transgenic plants, is being used to study the specific function of these genes and their role in plant acclimation or adaptation to water deficit. However, because plant responses to stress are complex, the functions of many of the genes are still unknown. Many of the traits that explain plant adaptation to drought - such as phenology, root size and depth, hydraulic conductivity and the storage of reserves - are those associated with plant development and structure, and are constitutive rather than stress induced. But a large part of plant resistance to drought is the ability to get rid of excess radiation, a concomitant stress under natural conditions. The nature of the mechanisms responsible for leaf photoprotection, especially those related to thermal dissipation, and oxidative stress are being actively researched. The new tools that operate at molecular, plant and ecosystem levels are revolutionising our understanding of plant response to drought, and our ability to monitor it. Techniques such as genome-wide tools, proteomics, stable isotopes and thermal or fluorescence imaging may allow the genotype-phenotype gap to be bridged, which is essential for faster progress in stress biology research.

Understanding plant responses to drought — from genes to the whole plant

Circular dichroism (CD) is an excellent tool for rapid determination of the secondary structure and folding properties of proteins that have been obtained using recombinant techniques or purified from tissues. The most widely used applications of protein CD are to determine whether an expressed, purified protein is folded, or if a mutation affects its conformation or stability. In addition, it can be used to study protein interactions. This protocol details the basic steps of obtaining and interpreting CD data, and methods for analyzing spectra to estimate the secondary structural composition of proteins. CD has the advantage that measurements may be made on multiple samples containing < or =20 microg of proteins in physiological buffers in a few hours. However, it does not give the residue-specific information that can be obtained by x-ray crystallography or NMR.

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Using circular dichroism spectra to estimate protein secondary structure

Fourier transform infrartd (FTIR) spectroscopy is an established tool for the structural character- ization of proteins. However, many potential pitfalls exist for the unwary investigator. In this review we critically assess the application of FIlR spectroscopy to the determination of protein structure by (1) outlining the principles underlying protein secondary structure determination by FZZR spectroscopy. (2) highhghting the situations in which FZZR spectroscopy should be considered the technique of choice, (3) discussing the manner in which experiments should be conducted to derive as much physiologically relevant information as possible, and (4) outlining current methods for the determination of secondary structure from infrared spectm of proteins,

The Use and Misuse of FTIR Spectroscopy in the Determination of Protein Structure

Plant adaptations to anaerobic stress

Enhanced development of gas-spaces beyond that due to the partial cell separation normally found in ground parenchymas and their derivatives creates tissue commonly termed “aerenchyma”. Aerenchyma can substantially reduce internal impedance to transport of oxygen, nitrogen and various metabolically generated gases such as carbon dioxide and ethylene, especially between roots and shoots. Such transport lessens the risk of asphyxiation under soil flooding or more complete plant submergence, and promotes radial oxygen loss from roots leading to oxidative detoxification of the rhizo-sphere. Aerenchyma can also increase methane loss from waterlogged sediments via plants to the atmosphere. This review of the formation and functioning of aerenchyma particularly emphasises research findings since 1992 and highlights prospects for the future. Regarding formation, attention is drawn to how little is known of the regulation and processes that create schizogenous aerenchyma with its complex cell arrangements and differential cell to cell adhesion. More progress has been made in understanding lysigenous aerenchyma development. The review highlights recent work on the processes that sense oxygen deficiency and ethylene signals, subsequent transduction processes which initiate cell death, and steps in protoplast and wall degeneration that create the intercellular voids. Similarities between the programmed cell death and its causes in animals and the predictable patterns of cell death that create lysigenous aerenchyma are explored. Recent findings concerning function are addressed in terms of the diffusion aeration of roots, rhizosphere oxygenation and sediment biogeochemistry, photosynthesis and ventilation, pressurised gas-flows and greenhouse gas emissions and aspects of ventilation related to secondary thickening.

Formation of Aerenchyma and the Processes of Plant Ventilation in Relation to Soil Flooding and Submergence

It has been estimated that wetlands occupy approximately 6% of the earth’s land surfaces (Maltby 1991). They comprise fresh, brackish and salt-water marshes, inland and coastal swamps, flood plains, and lowland and upland mires (fen, bogs), as well as agricultural wetlands such as rice paddy. On a smaller scale there are constructed wetlands valued for their role in the purification of domestic, agricultural and industrial effluents (Cooper & Findlater 1990). In addition to these examples, occasional soil flooding and even a degree of submergence can be a common though unwelcome feature of non-wetland agriculture. Wetlands are usually characterized by permanent or long-term soil flooding, but often the vegetation may be wholly or partly submerged; in the lower reaches of coastal marshes this may be a daily or twice daily occurrence. Indeed, since wetlands are found world-wide and at most altitudes, flooding regimes can vary enormously; not only do the seasonal timing, duration and depth of flooding differ, but so too do light and temperature regimes and sediment type—factors which strongly interact with flooding to influence vegetation. The large numbers and wide variety of vascular plants indigenous to wetlands reflect this variety in habitat features; species range from wholly submerged aquatics of pools, rivers, coastal and lake margins through to the large tree species of the flood plain forests of the Americas and Africa. In view of this variety in both plant and habitat, a whole spectrum of flood-related stresses might be anticipated; similarly one might expect to find a number of flood-tolerance strategies.

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Michael B. Jackson

Papers

The Use and Misuse of FTIR Spectroscopy in the Determination of Protein Structure

Plant adaptations to anaerobic stress

Formation of Aerenchyma and the Processes of Plant Ventilation in Relation to Soil Flooding and Submergence

Mechanisms of flood tolerance in plants

CHAPTER 3 – Effects of Flooding on Growth and Metabolism of Herbaceous Plants