Understanding Of Desiccation Tolerance Research Articles

Mechanisms of Desiccation Tolerance: Themes and Variations in Brine Shrimp, Roundworms, and Tardigrades.

Water is critical for the survival of most cells and organisms. Remarkably, a small number of multicellular animals are able to survive nearly complete drying. The phenomenon of anhydrobiosis, or life without water, has been of interest to researchers for over 300 years. In this review we discuss advances in our understanding of protectants and mechanisms of desiccation tolerance that have emerged from research in three anhydrobiotic invertebrates: brine shrimp (Artemia), roundworms (nematodes), and tardigrades (water bears). Discovery of molecular protectants that allow each of these three animals to survive drying diversifies our understanding of desiccation tolerance, and convergent themes suggest mechanisms that may offer a general model for engineering desiccation tolerance in other contexts.

Introduction to desiccation biology: from old borders to new frontiers.

A special issue reviews the recent progress made in our understanding of desiccation tolerance across various plant and animal kingdoms. It has been known for a long time that seeds can survive near absolute protoplasmic dehydration through air drying and complete germination upon rehydration because of their desiccation tolerance. This property is present both in prokaryotes and eukaryotes across all life kingdoms. These dry organisms suspend their metabolism when dry, are extremely tolerant to acute environmental stresses and are relatively stable during long periods of desiccation. Studies aiming at understanding the mechanisms of survival in the dry state have emerged during the past 40years, moving from in vitro to genomic models and comparative genomics, and from a view that tolerance is an all-or-nothing phenomenon to a quantitative trait. With the prospect of global climate change, understanding the mechanisms of desiccation tolerance appears to be a promising avenue as a prelude to engineering crops for improved drought tolerance. Understanding desiccation is also useful for seed banks that rely on dehydration tolerance to preserve plant genetic resources in the form of these propagules. Articles in this special issue explore the recent progress in our understanding of desiccation tolerance, including the evolutionary mechanisms that have been adopted across various plant (algae, lichens, seeds, resurrection plants) and animal model systems (Caenorhabditis elegans, brine shrimp). We propose that the term desiccation biology defines the discipline dedicated to understand the desiccation tolerance in living organisms as well as the limits and time constraints thereof.

Desiccation tolerance: From genomics to the field

Desiccation tolerance is defined as the ability to survive the removal of all, or almost all the cellular water without irreversible damage. It confers to dried organisms the ability to survive extreme conditions of the environment and to stay alive in a suspended animation for long periods of time. The biotechnological potential of anhydrous biology has been recognized for more than 60 years. With the fast development of “omics” technologies, it is now possible to better appreciate the biotechnological promises that can be made from the understanding of desiccation tolerance. This review will discuss the impact of post-genomics tools on identifying genes or gene products, and will give a comprehensive overview of the agronomical and biotechnological applications. We propose the term desiccomics to define the approach consisting of combining “omics” approaches to address the specific issues associated with the dry state.

Black, M. and Pritchard, H.W. (eds). Desiccation and survival in plants. Drying without dying

This excellent volume provides a very readable and comprehensive coverage of desiccation tolerance in plants. The opening chapter, from which the subtitle ‘Drying without dying’ is drawn, gives a splendid overview of what desiccation tolerance is and how plants accommodate this potentially lethal stress. It includes a history of research into plant desiccation and the development of ideas, its occurrence within the plant kingdom and its ecological significance. The subsequent chapters build masterfully upon this introduction, in an almost seamless manner that could lead one to believe that the whole book was written by only one or two authors. Such is not the case, for many experts in the field have contributed to this publication. The book is divided into broad subject areas which emphasize methodology, the biology of dehydration and tolerance mechanisms. A useful summarizing and prospects chapter is followed by a valuable glossary of terms, an unusual feature of a large taxonomic index that includes all of the species written about in the book, and a conventional index. The chapters devoted to methodology incorporate techniques for studying water relations under stress, ranging from the simple measuring of water content to sophisticated thermodynamic determinations and advanced models; desiccation and rehydration techniques are detailed, as are ways of measuring survivability; and for a neophyte like myself in the technology of biophysical and cellular methods of quantifying the response of plants to desiccation, an enlightening explanation of the meaning of, and principles behind, such challenging acronyms as ST‐EPR, NMR, FTIR and DSC. In addition, the opening chapter in this section contains a useful appendix with practical information, such as, for example, the concentrations of saturated salt solutions and glycerol that are needed to produce atmospheres of different relative humidities, the water potential of NaCl at different temperatures, and how to make solutions of salts and polyethylene glycol of various water potentials. I can envisage these pages being photocopied and pinned above laboratory benches around the world. The section on the biology of dehydration begins with a chapter on the sensitivity, or lack of, to desiccation of recalcitrant and orthodox seeds during development, and is followed by a shorter chapter on desiccation tolerance in pollen and the spores of lower plants. The differences in the depth of understanding of this phenomenon between seeds and pollen/spores are quite striking, with the former having attracted a much greater interest from the molecular standpoint. Desiccation‐tolerant vascular plants and mosses have played an important role in adding to our understanding of desiccation tolerance, and it is fitting that a chapter on their biology is included; the number of desiccation‐tolerant vascular plants is growing, and the current list of species spans several pages. Perhaps more consideration should also have been given here, or elsewhere, to covering tolerant lichens, algae and blue‐green algae, which receive a mention in the first chapter but whose biology is not elaborated upon later in the book. From a metabolic standpoint, at least as much is known about their responses to drying as about those of pollen and spores, for example. The final chapter in this section is on systematic and evolutionary aspects of desiccation tolerance in seeds, in which the questions are addressed as to when this phenomenon arose and whether it has been a continuous trait since then. The last collection of chapters, on the consequences of desiccation to plants, include the type of damage that plants must withstand, how they avoid or cope with this and how repair to damage is effected. Mechanical, cellular and subcellular changes are expertly detailed in all chapters, with emphases being appropriately on membrane integrity and water states, the synthesis of protective low molecular mass molecules, proteins and key metabolic enzymes, and the integrity of the genome. In addition to the informative text, these chapters contain very useful summarizing diagrams and tables that help the reader through the complexities of the subject. In some respects, the chapter on desiccation tolerance in developing seeds belongs here too because of the similarities in metabolic responses of these propagules to drying. This book should be found on the shelves of all those who are researching into or are interested in plant desiccation. It also should have a broader appeal, to those interested in plant stress from an agronomic and ecological perspective, for example. The book is likely be the standard reference in the area of desiccation tolerance for many years to come, even though some aspects will inevitably become dated as research continues to advance. The quality of writing, editing and presentation is very high, with many useful illustrations and summaries; the product is well worth its substantial price tag.