Plant Hormones
Beschreibung
Plant hormones play a crucial role in controlling the way in which plants grow and develop. While metabolism provides the power and building blocks for plant life, it is the hormones that regulate the speed of growth of the individual parts and integrate them to produce the form that we recognize as a plant.
This book is a description of these natural chemicals: how they are synthesized and metabolized, how they act at both the organismal and molecular levels, how we measure them, a description of some of the roles they play in regulating plant growth and development, and the prospects for the genetic engineering of hormone levels or responses in crop plants. This is an updated revision of the third edition of the highly acclaimed text. Thirty-three chapters, including two totally new chapters plus four chapter updates, written by a group of fifty-five international experts, provide the latest information on Plant Hormones, particularly with reference to such new topics as signal transduction, brassinosteroids, responses to disease, and expansins. The book is not a conference proceedings but a selected collection of carefully integrated and illustrated reviews describing our knowledge of plant hormones and the experimental work that is the foundation of this information.
The Revised 3 rd Edition adds important information that has emerged since the original publication of the 3 rd edition. This includes information on the receptors for auxin, gibberellin, abscisic acid and jasmonates, in addition to new chapters on strigolactones, the branching hormones, and florigen, the flowering hormone.
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F1. Jasmonates
Gregg A. Howe
MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA. E-mail: howeg@msu.edu
INTRODUCTION
Jasmonic acid (JA1) and its volatile methyl ester, MeJA, are fatty acidderived cyclopentanones that occur ubiquitously in the plant kingdom. Since the discovery of jasmonates (JAs) in plants over 40 years ago, our understanding of the biosynthesis and physiological function of these compounds has been marked by several major developments. Experiments performed in the 1980s elucidated the JA biosynthetic pathway and demonstrated that exogenous JAs exert effects on a wide range of physiological processes.
The discovery in the early 1990s that JAs act as potent signals for the expression of defensive proteinase inhibitors (PIs) aroused intense interest in the function of hormonally active JAs in plant defense. Research in the past decade has led to several key developments, including identification of genes encoding most of the JA biosynthetic enzymes and discovery of novel biologically active JAs. Identification of a large collection of JA biosynthesis and response mutants has provided important tools to assess the role of JAs in plant developmental and defenserelated processes.
The widespread occurrence of JAs in plants and some lower eukaryotes, together with their capacity to regulate physiological processes in animals (e.g., insects), reinforces the notion that JAs are of general biological interest. JASMONATE BIOSYNTHESIS Oxylipin Metabolism in Plants and Animals Jasmonates belong to the family of oxygenated fatty acid derivatives, collectively called oxylipins, which are produced via the oxidative metabolism of polyunsaturated fatty acids.
In animals, members of the eicosanoid (C20) group of lipid mediators are synthesized from arachidonic acid and function as regulators of cell differentiation, immune responses, and homeostasis. In plants, oxygenated compounds derived mainly from C18 α- linolenic acid (18:3) control a similarly broad spectrum of developmental and defense-related processes (4, 13, 19, 30, 47, 48). The biochemical logic underlying the synthesis of oxylipins in plants and animals is remarkably similar.
Species in both kingdoms utilize cytochromes P450, lipoxygenase (LOX), and cyclooxygenase or cyclooxygenase-like (e.g., plant α-dioxygenase) activities to oxidize polyunsaturated fatty acid substrates (3). The resulting oxygenated fatty acids are further metabolized by various enzymatic and non-enzymatic systems to an array of intermediates and end products. These compounds are typically synthesized de novo in specific cell types upon activation of lipases that release fatty acids from membrane lipids."
