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Open Access Highly Accessed Research article

Imaging plant cell death: GFP-Nit1 aggregation marks an early step of wound and herbicide induced cell death

Sean R Cutler1* and Chris R Somerville2

Author Affiliations

1 Department of Botany, University of Toronto, 25 Willcocks St., Toronto, Ontario, M5S 3B2, Canada

2 Carnegie Institution, Department of Plant Biology, 260 Panama Street, Stanford, CA 94305, USA

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BMC Plant Biology 2005, 5:4  doi:10.1186/1471-2229-5-4

Published: 29 March 2005

Abstract

Background

A great deal is known about the morphological endpoints of plant cell death, but relatively little is known about its sequence of events and / or its execution at the biochemical level. Live cell imaging using GFP-tagged markers is a powerful way to provide dynamic portraits of a cellular process that can in turn provide a descriptive foundation valuable for future biochemical and genetic investigations.

Results

While characterizing a collection of random GFP-protein fusion markers we discovered that mechanical wounding induces rapid aggregation of a GFP-Nitrilase 1 fusion protein in Arabidopsis cells directly abutting wound sites. Time-lapse imaging of this response shows that the aggregation occurs in cells that subsequently die 30 – 60 minutes post-wounding, indicating that GFP-Nit1 aggregation is an early marker of cell death at wound sites. Time-lapse confocal imaging was used to characterize wound-induced cell death using GFP-Nit1 and markers of the nucleus and endoplasmic reticulum. These analyses provide dynamic portraits of well-known death-associated responses such as nuclear contraction and cellular collapse and reveal novel features such as nuclear envelope separation, ER vesiculation and loss of nuclear-lumen contents. As a parallel system for imaging cell death, we developed a chemical method for rapidly triggering cell death using the herbicides bromoxynil or chloroxynil which cause rapid GFP-Nit1 aggregation, loss of nuclear contents and cellular collapse, but not nuclear contraction, separating this response from others during plant cell death.

Conclusion

Our observations place aggregation of Nitrilase 1 as one of the earliest events associated with wound and herbicide-induced cell death and highlight several novel cellular events that occur as plant cells die. Our data create a detailed descriptive framework for future investigations of plant cell death and provide new tools for both its cellular and biochemical analysis.