 Videoclip 1 |
 Videoclip 2 |
Disease resistance in plants is often expressed as the hypersensitive response (HR), a rapid, localized plant cell death that is associated with the restriction of pathogen growth. This response is ubiquitous among flowering plants, and is considered to involve a form of programmed cell death. Although it can be triggered by a wide range of micro-organisms, the death process can be phenotypically quite different in different systems. This is illustrated in the three videoclips shown here. To compare the HR with developmental programmed cell death in differentiating tracheary elements, visit Dr. Alan Jones' web site (http://www.unc.edu/depts/joneslhp/pcd/). For a variety of articles on the HR, see the July 1999 issue of PMPP.
Videoclips 1 and 2 show late stages of the hypersensitive cell death (speeded up about 24X) in cowpea vein epidermal cells caused by invasion of the monokaryon of the rust fungus, Uromyces vignae. After cytoplasmic streaming ceases in the plant cell, cell death becomes irreversible. Particles show Brownian motion in the vacuole and then become still (Videoclip 1). Several hours later, the protoplast collapses (Videoclip 2) after which metabolic activity in the neighbouring living cells result in the dead cell becoming autofluorescent and brown. The fungus is the spherical structure in the top right part of the cell. For further details, see Heath et al. (1997) New Phytologist 138:251–263.
Videoclip 1 |
Videoclip 2 |
Videoclip 3 shows a late stage in the hypersensitive cell death of potato vein epidermal cells caused by invasion of the oomycete, Phytophthora infestans. The plant cytoplasm and nucleus aggregate around the pathogen (spherical structure on lower right of cell) and cytoplasmic streaming ceases. The videoclip shows the subsequent sudden expansion and collapse of the protoplasmic conglomerate within 26s, followed rapidly by the expansion and collapse of the pathogen. For further details, see Freytag et al. (1994) Planta 194:123–135. Video scene of programmed cell death in potato epidermal cells Copyright ©1994 by Dr. Elmon Schmelzer. All rights reserved. Used by permission.
