The last 30 years have been heady times in the field (actually mainly in the laboratory, but see later) for genomics and genetic engineering directed to understanding and developing abiotic stress adaptation in plants. They have stood the old order on its head. Once, plant physiology and biochemistry provided information about how plants responded to the rapid and often very substantial fluctuations in environment – temperature, light, salinity, drought, all ‘abiotic’ factors that elicit responses in and by the plant according to their range of magnitude and combinations. But such analysis was not directly aimed at improving the plants' performance to one or more environmental factors. Rather, this information was assimilated by agronomists into the then current applied technology, improving the efficiency of production by plants and also the use of resources. Breeders also utilised the information in many ways within breeding programmes, selecting lines incorporating genes from widely different sources under the conditions of the target environment for improvement of plants as crops. This tested the genotype × environmental (G × E) interactions that are such a feature of crop production. Because plants evolved in particular environments, with specific combinations and ranges of conditions, their growth and production of dry matter and yield of fuels, fibre and food – required to satisfy the insatiable appetite of the burgeoning human population of this sorely afflicted planet – are severely curtailed by environmental conditions outside the range to which they are adapted. The smaller the supply of one (or more) ‘resource’, generally the smaller the crop's production. Selection and, more recently, breeding and selection have made great advances in providing genotypes of crops adapted to a wide range of conditions (abiotic and biotic factors): very roughly, improved agronomy and breeding contributing 50 : 50 to the massive improvement of yields in industrial cropping systems.
However, it is still impossible to grow wheat or maize in the Arctic Circle or in the Sahara. This is clearly unsatisfactory! Humanity demands that agriculture must operate at full production everywhere to satisfy its demands. Now that the genomes of many species are described and the expanding technology of molecular biology allows them to be altered at will (or almost), it is inevitable that they should be combined with the accumulated knowledge of biochemistry and physiology in order to specifically manipulate genomes to induce plant adaptation to abiotic stress and to overcome those annoying G × E problems. This is truly ‘engineering’ – with explicit targets based on full (or more often partial) understanding of the complex metabolic systems, not gene shuffling in a ‘black box’, as done by breeders. The claims for the power of this new approach have been truly substantial, including that ‘fully drought-resistant crops’ can be made by molecular engineering techniques ‘next year’ and ‘without the need for any physiological input’ (personal communications from various sources).
Behind this hype lies a great deal of fascinating and important science. There has been an explosion in information, and understanding, of the plant mechanisms related to ‘abiotic stresses’ and keeping track has proved difficult: which is where this book comes in. The cover sets out a rich feast: ‘Environmental insults … pose major threats to agriculture … the aim [is] to … manipulate plant performance … to withstand stress conditions’. It claims a ‘… holistic view of the general principles of stress perception, signal transduction and regulation of gene expression” and considers ‘how stress-tolerant model plants or crops have been or are being raised through plant breeding and genetic engineering approaches … This book serves as a complete package on the basics and applications for abiotic stress response pathways in plants’. Indeed, at over 520 pages, with 23 predominantly multi-author chapters arranged in four parts, it is a considerable compendium of information and references (up to about 2008). It is well, but not abundantly, illustrated and there are colour plates – but all in the front of the book: they also appear in black and white in the relevant chapters; a strange quirk of questionable value. The excellent authors are of wide international range, with India well represented. After a short, general overview chapter, Part I considers ‘Stress Perception and Signal transduction’, covering sensors and signal transducers in cyanobacteria, abscisic acid, calcium and reactive oxygen species. There is also some consideration of biotic stresses, the roles of protein kinases and phosphatases, and then the influence of nitrogen sources on root-to-shoot signalling under drought. Part II focuses on ‘Stress regulation of gene expression’, with chapters on complexities in gene expression, then promoters and transcription factors, and epigenetic regulation. Part III, ‘Physiology and metabolism’, deals with ion homeostasis, glutathione homeostasis, water balance and stomatal movements, followed by responses to macronutrient deprivation, osmolyte regulation and programmed cell death. Part IV, ‘Overcoming stress’, deliberates varietal improvements in crops, mainly salinity and rice, transgenic approaches, marker-assisted breeding, and stress and mutations, followed by one short consideration of systems biology and another on climate change.
The chapters are, therefore, rather disparate, individually worthy of consideration but of variable length and quality. Some offer very detailed statements of what the literature contains with many references (one has approx. 500), but not always very analytical in approach. Some are very general, leaving a feeling that a bit more detail would have been useful. It is never possible to satisfy reviewers! Because of the wide range in topics there is an element of the ‘holistic approach’, but readers will have to work hard to find a strong common theme or logical, well-stated models bringing the chapters together. For example, there is a strong emphasis on what have become traditional assumptions (perhaps even dogmas?) in molecular biology that ‘abiotic stress resistance’ will be (indeed has been) achieved. Evidence of this comes mainly from many laboratory studies and much less from complex field conditions: more discussion of such aspects would have elevated the volume above the copious similar literature. Chapters on breeding with modern techniques (e.g. of rice for saline conditions) and of marker-assisted breeding are related to crops in the field but the link to earlier, more molecular chapters is tenuous, and environmental aspects are only touched on. This is inevitable with a wide range of individual chapters and no strong, summarising or theme-setting articles. Some basic aspects have been passed over, presumably because they are regarded as unnecessary. For example, what is ‘abiotic stress tolerance’? Indeed, what is an abiotic stress – the environmental factor per se is not a stress: only when it affects the plant does the plant exhibit ‘stress responses’, i.e. abnormalities in growth, metabolism, etc. So there is a need to quantify the environmental factor(s) and the plant's responses. The inadequate information about environmental factors in the field, and very limited consideration of how the basic cellular mechanisms respond and may impinge on crops, is clearly a weakness if the aim is to relate how genetic modification has (or may) produce adapted crops: how ‘resistant’ or ‘tolerant’ to abiotic conditions modified plants are requires quantification.
The book is aimed at ‘late undergraduate through to beginning researchers’ in many areas of science and technology. I suspect that many chapters will require more experience than this suggests. Most readers will read individual chapters aligned with their interests to get background and references. They should take the time to browse others for there is much of value. However, an overview, holistic, approach is not achieved (a weakness for the target audience, possibly) and perhaps could not be in a collection of review chapters of this type. Given the cost of the book, and the rapidly changing technology, science and concepts, it is most suited to libraries, where it should find readers and will be useful.