Kent J. Bradford

Physiological Responses to Moderate Water Stress

On a global basis, water is a paramount factor in determining the distribution of species, and the responses and adaptations of a species to water stress are critical for its success in any environmental niche. Numerous studies have reported a myriad of changes elicited by water stress. The changes observed are dependent on the species under study and on the severity, duration, and time course of the stress. Before reviewing the changes in detail, we will first present an overview of stress and responses using the stress-strain concept of physics. Next, we will discuss specific water-related parameters for quantifying plant water status and briefly consider how changes in the parameters may affect plant functions. This is followed by the main body which first reviews and analyzes selected responses to water stress and then examines the integrated adaptive behavior of whole plants.

Structure and Composition

Seeds are very diverse in their shape and size. In the mature state they contain an embryo, the next generation of plant, surrounded by a protective structure (the seed and/or fruit coat) and, in species in which the nutritive reserves are not stored within the cotyledons, by an alternative storage tissue (endosperm, perisperm, or megagametophyte). Most seeds contain large and characteristic quantities of polymeric reserves. The major ones are carbohydrates, oils, and proteins, with minor amounts of phosphate-rich phytin. Starch, a polymer of glucose, is the most common form of stored carbohydrate, contained within cytoplasmic starch granules; less common are the hemicelluloses, stored in secondary cell walls, usually as mannan polymers. Oils are triacylglycerols, each composed of glycerol and three fatty acids that are specific to the oil; these are present within oil bodies. Storage proteins, of which there are three types, albumins, globulins, and prolamins, are sequestered in protein storage vacuoles. These reserves are vital components of human and animal diets, and their production in crops is a basis of agriculture.

Applications of hydrothermal time to quantifying and modeling seed germination and dormancy

Abstract Knowledge and prediction of seasonal weed seedling emergence patterns is useful in weed management programs. Seed dormancy is a major factor influencing the timing of seedling emergence, and once dormancy is broken, environmental conditions determine the rate of germination and seedling emergence. Seed dormancy is a population-based phenomenon, because individual seeds are independently sensing their environment and responding physiologically to the signals they perceive. Mathematical models based on characterizing the variation that occurs in germination times among individual seeds in a population can describe and quantify environmental and after-ripening effects on seed dormancy. In particular, the hydrothermal time model can describe and quantify the effects of temperature and water potential on seed germination. This model states that the time to germination of a given seed fraction is inversely proportional to the amount by which a given germination factor (e.g., temperature or water potential) exceeds a threshold level for that factor. The hydrothermal time model provides a robust method for understanding how environmental factors interact to result in the germination phenotype (i.e., germination pattern over time) of a seed population. In addition, other factors that influence seed dormancy and germination act by causing the water potential thresholds of the seed population to shift to higher or lower values. This relatively simple model can describe and quantify the germination behavior of seeds across a wide array of environmental conditions and dormancy states, and can be used as an input to more general models of seed germination and seedling emergence in the field.

Regulating transgenic crops sensibly: lessons from plant breeding, biotechnology and genomics

The costs of meeting regulatory requirements and market restrictions guided by regulatory criteria are substantial impediments to the commercialization of transgenic crops. Although a cautious approach may have been prudent initially, we argue that some regulatory requirements can now be modified to reduce costs and uncertainty without compromising safety. Long-accepted plant breeding methods for incorporating new diversity into crop varieties, experience from two decades of research on and commercialization of transgenic crops, and expanding knowledge of plant genome structure and dynamics all indicate that if a gene or trait is safe, the genetic engineering process itself presents little potential for unexpected consequences that would not be identified or eliminated in the variety development process before commercialization. We propose that as in conventional breeding, regulatory emphasis should be on phenotypic rather than genomic characteristics once a gene or trait has been shown to be safe.

Compliance Costs for Regulatory Approval of New Biotech Crops

The regulatory approval process for new biotech crop varieties is said to be unduly slow and expensive, presenting important barriers to the development of new cropping technologies. To date, however, the private and social costs have not been analyzed or measured, let alone compared with alternatives. This chapter reports initial findings from our continuing project on the costs of regulatory compliance for biotech crops. In this chapter we describe and document the regulatory requirements, and we provide estimates of representative compliance costs for key biotechnologies based on confidential data supplied to us by several major biotech companies.

Nomenclature for members of the expansin superfamily of genes and proteins

Hans Kende*, Kent J. Bradford, David A. Brummell, Hyung-Taeg Cho, Daniel J. Cosgrove, Andrew J. Fleming, Chris Gehring, Yi Lee, Simon McQueen-Mason, Jocelyn K.C. Rose and Laurentius A.C.J. Voesenek MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA (*author for correspondence; e-mail hkende@msu.edu); Seed Biotechnology Center, University of California, Davis CA 95616, USA; Crop and Food Research, Private Bag 11600, Palmerston North, 5301, New Zealand; School of Biosciences and Biotechnology, Chungnam National University, Daejeon 305-764, Republic of Korea; Department of Biology, 208 Mueller Laboratory, Pennsylvania State University, University Park, PA 16802, USA; Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK; University of the Western Cape, Department of Biotechnology, Private Bag X17, Bellville 7535, South Africa; Department of Tobacco Science, Chungbuk National University, 48 Gaesin-dong Hungduk-ku, Chongju 361-763, Republic of Korea; Biology Department, University of York, PO Box 373, York, YO10 5YW, UK; Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA; Plant Ecophysiology, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands

Seed development, dormancy and germination.

Chapter 1. Genetic Control of Seed Development and Seed Mass. Masa--aki Ohto1, Sandra L. Stone2 and John J. Harada2. 1Department of Plant Sciences, College of Agricultural and Environmental Sciences and 2Section of Plant Biology, College of Biological Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA . Chapter 2. Seed Coat Development and Dormancy. Isabelle Debeaujon, Loic Lepiniec, Lucille Pourcel and Jean--Marc Routaboul. Laboratoire de Biologie des Semences, Unite Mixte de Recherche 204 Institut National de la Recherche Agronomique/Institut National Agronomique Paris--Grignon, 78026 Versailles, France. Chapter 3. Definitions and Hypotheses of Seed Dormancy. Henk W.M. Hilhorst. Laboratory of Plant Physiology, Wageningen University, Arboretumlaan 4, 6703 BD, Wageningen, The Netherlands . Chapter 4. Modeling of Seed Dormancy. Phil S. Allen1, Roberto L. Benech--Arnold2, Diego Batlla2 and Kent J. Bradford3. 1Department of Plant & Animal Sciences, Brigham Young University, 275 WIDB, Provo, UT 84602--5253, USA 2IFEVA--Catedra de Cerealicultura, Facultad de Agronomia, Universidad de Buenos Aires/CONICET,Av. San Martin 4453, 1417 Buenos Aires, Argentina 3Seed Biotechnology Center, University of California, One Shields Avenue, Davis, CA 95616--8780, USA . Chapter 5. Genetic Aspects of Seed Dormancy. Leonie Bentsink1, Wim Soppe2 and Maarten Koornneef2,3. 1Department of Molecular Plant Physiology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands 2 Max Planck Institute for Plant Breeding Research, Carl--von--Linne--Weg 10, 50829 Cologne, Germany and 3Laboratory of Genetics, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands. Chapter 6. Lipid Metabolism in Seed Dormancy. Steven Penfield, Helen Pinfield--Wells and Ian A. Graham. Centre for Novel Agricultural Products, Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. . Chapter 7. Nitric Oxide in in Seed Dormancy and Germination. Paul C. Bethke1, Igor G.L. Libourel2 and Russell L. Jones1. 1Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720--3102, USA and 2Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA. Chapter 8. A Merging of Paths: Abscisic Acid and Hormonal Cross--talk in the Control of Seed Dormancy Maintenance and Alleviation. J. Allan Feurtado and Allison R. Kermode. Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada V5A 1S6. Chapter 9. Regulation of ABA and GA Levels during Seed Development and Germination in Arabidopsis. Shinjiro Yamaguchi, Yuji Kamiya and Eiji Nambara. Plant Science Center, RIKEN, Growth Physiology Group, Laboratory for Cellular Growth & Development, 1--7--22 Suehirocho, Tsurumi--ku, Yokohama, 230--0045 Japan. Chapter 10. De--repression of Seed Germination by GA Signaling. Camille M. Steber. U.S. Department of Agriculture--Agricultural Research Service and Department of Crop and Soil Science and Graduate Program in Molecular Plant Sciences, Washington State University, Pullman, WA 99164--6420, USA. Chapter 11. Mechanisms and Genes Involved in Germination Sensu Stricto. Hiroyuki Nonogaki1, Feng Chen2 and Kent J. Bradford3. 1Department of Horticulture, Oregon State University, Corvallis, OR 97331, USA 2Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996--4561, USA 3Seed Biotechnology Center, University of California, One Shields Avenue, Davis, CA 95616--8780, USA. Chapter 12. Sugar and Abscisic Acid Regulation of Germination and Transition to Seedling Growth. Bas J.W. Dekkers and Sjef C.M. Smeekens. Department of Molecular Plant Physiology, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.

The case for strategic international alliances to harness nutritional genomics for public and personal health

Nutrigenomics is the study of how constituents of the diet interact with genes, and their products, to alter phenotype and, conversely, how genes and their products metabolise these constituents into nutrients, antinutrients, and bioactive compounds. Results from molecular and genetic epidemiological studies indicate that dietary unbalance can alter gene-nutrient interactions in ways that increase the risk of developing chronic disease. The interplay of human genetic variation and environmental factors will make identifying causative genes and nutrients a formidable, but not intractable, challenge. We provide specific recommendations for how to best meet this challenge and discuss the need for new methodologies and the use of comprehensive analyses of nutrient-genotype interactions involving large and diverse populations. The objective of the present paper is to stimulate discourse and collaboration among nutrigenomic researchers and stakeholders, a process that will lead to an increase in global health and wellness by reducing health disparities in developed and developing countries.

The public-private structure of intellectual property ownership in agricultural biotechnology.

New findings indicate that there may be benefits from more collaborative models of intellectual property management in the public sector.

Class I Chitinase and β-1,3-Glucanase Are Differentially Regulated by Wounding, Methyl Jasmonate, Ethylene, and Gibberellin in Tomato Seeds and Leaves

Class I chitinase (Chi9) and β-1,3-glucanase (GluB) genes are expressed in the micropylar endosperm cap of tomato (Lycopersicon esculentum) seeds just before radicle emergence through this tissue to complete germination. In gibberellin (GA)-deficient mutant (gib-1) seeds, expression of Chi9 and GluB mRNA and protein is dependent upon GA. However, as expression occurs relatively late in the germination process, we investigated whether the genes are induced indirectly in response to tissue wounding associated with endosperm cap weakening and radicle protrusion. Wounding and methyl jasmonate (MeJA) induced Chi9 expression, whereas ethylene, abscisic acid, sodium salicylate, fusicoccin, or β-aminobutyric acid were without effect. Chi9 expression occurred only in the micropylar tissues when seeds were exposed to MeJA or were wounded at the chalazal end of the seed. Expression of Chi9, but not GluB, mRNA was reduced in germinating seeds of the jasmonate-deficient defenseless1 tomato mutant and could be restored by MeJA treatment. Chi9 expression during germination may be associated with “wounding” from cell wall hydrolysis and weakening in the endosperm cap leading to radicle protrusion, and jasmonate is involved in the signaling pathway for this response. Among these treatments and chemicals (other than GA), only MeJA and wounding induced a low level of GluB expression in gib-1 seeds. However, MeJA, wounding, and particularly ethylene induced both genes in leaves, whereas GA induced only Chi9 in leaves. Although normally expressed simultaneously during tomato seed germination, Chi9 and GluB genes are regulated distinctly and tissue specifically by hormones and wounding.