title: Morphological classification of plant cell deaths.
abstract: Programmed cell death (PCD) is an integral part of plant development and of responses to abiotic stress or pathogens. Although the morphology of plant PCD is, in some cases, well characterised and molecular mechanisms controlling plant PCD are beginning to emerge, there is still confusion about the classification of PCD in plants. Here we suggest a classification based on morphological criteria. According to this classification, the use of the term 'apoptosis' is not justified in plants, but at least two classes of PCD can be distinguished: vacuolar cell death and necrosis. During vacuolar cell death, the cell contents are removed by a combination of autophagy-like process and release of hydrolases from collapsed lytic vacuoles. Necrosis is characterised by early rupture of the plasma membrane, shrinkage of the protoplast and absence of vacuolar cell death features. Vacuolar cell death is common during tissue and organ formation and elimination, whereas necrosis is typically found under abiotic stress. Some examples of plant PCD cannot be ascribed to either major class and are therefore classified as separate modalities. These are PCD associated with the hypersensitive response to biotrophic pathogens, which can express features of both necrosis and vacuolar cell death, PCD in starchy cereal endosperm and during self-incompatibility. The present classification is not static, but will be subject to further revision, especially when specific biochemical pathways are better defined.
authors.affiliation: Mann Laboratory, Department of Plant Sciences, University of California, Davis, CA 95616, USA. wgvandoorn@ucdavis.edu
authors.forename: W G
authors.initials: WG
authors.lastname: van Doorn
authors.forename: E P
authors.initials: EP
authors.lastname: Beers
authors.forename: J L
authors.initials: JL
authors.lastname: Dangl
authors.forename: V E
authors.initials: VE
authors.lastname: Franklin-Tong
authors.forename: P
authors.initials: P
authors.lastname: Gallois
authors.forename: I
authors.initials: I
authors.lastname: Hara-Nishimura
authors.forename: A M
authors.initials: AM
authors.lastname: Jones
authors.forename: M
authors.initials: M
authors.lastname: Kawai-Yamada
authors.forename: E
authors.initials: E
authors.lastname: Lam
authors.forename: J
authors.initials: J
authors.lastname: Mundy
authors.forename: L A J
authors.initials: LA
authors.lastname: Mur
authors.forename: M
authors.initials: M
authors.lastname: Petersen
authors.forename: A
authors.initials: A
authors.lastname: Smertenko
authors.forename: M
authors.initials: M
authors.lastname: Taliansky
authors.forename: F
authors.initials: F
authors.lastname: Van Breusegem
authors.forename: T
authors.initials: T
authors.lastname: Wolpert
authors.forename: E
authors.initials: E
authors.lastname: Woltering
authors.forename: B
authors.initials: B
authors.lastname: Zhivotovsky
authors.forename: P V
authors.initials: PV
authors.lastname: Bozhkov
mesh_terms: D000818:Animals; D016923:Cell Death / Q000502:physiology*; D059828:Plant Cells; D018521:Plant Physiological Phenomena; D010944:Plants / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism