Cell Signaling during Cold, Drought, and Salt Stress.

Cell Signaling during Cold, Drought, and Salt Stress. - The...

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The Plant Cell, S165–S183, Supplement 2002, www.plantcell.org © 2002 American Society of Plant Biologists Cell Signaling during Cold, Drought, and Salt Stress Liming Xiong, Karen S. Schumaker, and Jian-Kang Zhu 1 Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721 INTRODUCTION Low temperature, drought, and high salinity are common stress conditions that adversely affect plant growth and crop production. The cellular and molecular responses of plants to environmental stress have been studied intensively (Thomashow, 1999; Hasegawa et al., 2000). Understanding the mechanisms by which plants perceive environmental signals and transmit the signals to cellular machinery to acti- vate adaptive responses is of fundamental importance to bi- ology. Knowledge about stress signal transduction is also vital for continued development of rational breeding and transgenic strategies to improve stress tolerance in crops. In this review, we first consider common characteristics of stress signal transduction in plants, and then examine some recent studies on the functional analysis of signaling com- ponents. Finally, we attempt to put these components and pathways into signal transduction networks that are grouped into three generalized signaling types. General Stress Signal Transduction Pathways A generic signal transduction pathway starts with signal per- ception, followed by the generation of second messengers (e.g., inositol phosphates and reactive oxygen species [ROS]). Second messengers can modulate intracellular Ca 2 1 levels, often initiating a protein phosphorylation cascade that finally targets proteins directly involved in cellular pro- tection or transcription factors controlling specific sets of stress-regulated genes (Figure 1). The products of these genes may participate in the generation of regulatory mole- cules like the plant hormones abscisic acid (ABA), ethylene, and salicylic acid (SA). These regulatory molecules can, in turn, initiate a second round of signaling that may follow the above generic pathway, although different components are often involved (Figures 1 and 2). Signal transduction requires the proper spatial and tem- poral coordination of all signaling molecules. Thus, there are certain molecules that participate in the modification, deliv- ery, or assembly of signaling components, but do not di- rectly relay the signal. They too are critical for the accurate transmission of stress signals. These proteins include pro- tein modifiers (e.g., enzymes for protein lipidation, meth- ylation, glycosylation, and ubiquitination), scaffolds, and adaptors (Xiong and Zhu, 2001) (Figure 1). Multiplicity of Abiotic Stresses as Signals for Plants and the Need for Multiple Sensors Low temperature, drought, and high salinity are very com- plex stimuli that possess many different yet related at- tributes, each of which may provide the plant cell with quite different information. For example, low temperature may im- mediately result in mechanical constraints, changes in activ-
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This note was uploaded on 08/01/2009 for the course 231 224-12 taught by Professor Mazik during the Spring '06 term at A.T. Still University.

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Cell Signaling during Cold, Drought, and Salt Stress. - The...

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