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Signal-mediated depolymerization of actin in pollen during the self-incompatibility response
Benjamin N Snowman1, David R Kovar, Galina Shevchenko
1School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
The Plant Cell
|October 9, 2002
Summary
Self-incompatibility (SI) in poppy pollen rapidly reduces filamentous actin (F-actin) levels, a sustained response mediated by calcium (Ca2+) signaling. This actin depolymerization likely inhibits pollen tube growth.
Area of Science:
- Plant biology
- Cell signaling
- Cytoskeleton dynamics
Background:
- Cellular communication relies on signal perception and integration.
- Self-incompatibility (SI) in field poppy pollen involves a calcium (Ca2+)-dependent cascade inhibiting incompatible pollen.
- SI responses trigger significant changes in the actin cytoskeleton.
Purpose of the Study:
- To quantify changes in filamentous actin (F-actin) levels during the SI response in field poppy pollen.
- To investigate the role of Ca2+ signaling in mediating actin depolymerization.
- To explore the involvement of profilin in Ca2+-dependent actin dynamics.
Main Methods:
- Measurement of F-actin levels in pollen before and during the SI response.
- Experimental induction of actin depolymerization using Ca2+-elevating treatments.
- Determination of cellular concentrations and binding constants for poppy pollen profilin.
Main Results:
- SI stimulation caused a rapid, large, and sustained reduction in F-actin levels for at least 1 hour.
- Artificial increases in cytosolic Ca2+ mimicked SI-induced actin depolymerization.
- Poppy pollen profilin exhibits Ca2+-dependent actin-sequestering activity.
Conclusions:
- SI induces stimulus-mediated F-actin depolymerization in plant cells, a rare phenomenon.
- Ca2+ signals are a key target for SI-induced actin depolymerization.
- Ca2+-mediated actin depolymerization is a proposed mechanism for SI-induced pollen tip growth inhibition.