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Evidence for an Extracellular Reception Site for Abscisic Acid in Commelina Guard Cells.
B. E. Anderson1, J. M. Ward, J. I. Schroeder
1Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116.
Plant Physiology
|April 1, 1994
Summary
Abscisic acid (ABA) primarily acts on the outside of plant guard cells to trigger stomatal closing during drought. Intracellular ABA alone does not cause stomatal closure, indicating an external receptor is key for this drought response.
Area of Science:
- Plant Physiology
- Molecular Biology
- Drought Stress Response
Background:
- Abscisic acid (ABA) is a crucial phytohormone regulating plant responses to drought stress, primarily by inducing stomatal closure.
- The precise location of ABA receptors in guard cells and the necessity of ABA transport into these cells remain poorly understood, hindering a complete mechanistic insight.
- Understanding ABA reception is vital for developing strategies to improve plant drought tolerance.
Purpose of the Study:
- To determine the primary site of abscisic acid (ABA) reception in guard cells.
- To investigate whether ABA needs to be transported into guard cells to elicit stomatal closure.
- To elucidate the mechanism of ABA-mediated stomatal regulation.
Main Methods:
- Microinjection of abscisic acid (ABA) into guard cells of Commelina communis L. at varying concentrations.
- Physiological assays measuring stomatal movements in response to microinjected and extracellular ABA.
- Guard cell viability assessment using neutral red staining and monitoring of stomatal opening.
Main Results:
- Microinjection of ABA into guard cells did not inhibit stomatal opening, indicating intracellular ABA alone is insufficient for this response.
- Extracellular application of ABA significantly inhibited stomatal opening, with efficacy dependent on pH, suggesting a role for extracellular receptors.
- Guard cell viability was maintained post-injection, validating the experimental conditions.
Conclusions:
- The primary site for abscisic acid (ABA) perception that leads to stomatal closure is located on the extracellular side of the guard cell plasma membrane.
- Intracellular ABA, under the tested conditions, does not appear to mediate stomatal closure, challenging previous assumptions.
- The pH-dependent action of extracellular ABA suggests a complex interaction possibly involving both extracellular and intracellular components in ABA signaling.