Poster: Organelle biogenesis
Abs #
637: Precursor protease vesicles (ricinosomes) are involved in the programmed cell death of the nucellus during castor oil seed development.
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Presenter: |
Greenwood, John S, jgreenwo@uoguelph.ca |
Authors | Greenwood, John S (A) Helm, Michael (B) Gietl, Christine (B) | | Affiliations: |
(A): University Of Guelph, Dept. of Botany
(B): Technincal University of Munich, Dept. of Botany
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Precursor protease vesicles (PPVs) are cellular compartments derived from the endoplasmic reticulum that contain precursors of cysteine proteinases. They have been most commonly found in the cells of seed storage tissues after germination (1-4). The mature cysteine proteinases assist in the programmed death of cells of the senescing storage tissue. Cys-EP, a PPV resident KDEL-tagged cysteine proteinase from germinated castor bean endosperm, is purported to have just such a function (3). However, evidence linking PPVs to senescence and programmed cell death in other, non-storage, tissues has been lacking (5).
During castor oil (Ricinus communis) seed development, the cells of the nucellus are sacrificed as the endosperm expands. Cell death is preceded by the fragmentation of genomic DNA and occurs in those cells lying immediately adjacent to the expanding endosperm. Using antibodies to Cys-EP, the enzyme was localized to very numerous small organelles within those nucellar cells lying up to three cells away from the endosperm. Occasionally labelling was diffuse and covered the entire cell, suggesting that the organelles had either lysed or had fused with the central vacuole. Electron microscopy revealed that Cys-EP was localized to ricinosomes (3), PPV compartments that retain ribosomes on the membrane after their formation. Thus, in castor bean, PPVs are also involved in the programmed death of cells of the nucellus, a maternal tissue that does not have a storage function.
1) Chrispeels, M.J.; Herman, E.M. (2000). Plant Physiol. 123: 1227 2) Hayashi et al. (2001) Plant Cell Physiol. 42: 894 3) Schmid et al. (2001) Proc. Natl. Acad. Sci. USA 98: 5353 4) Toyooka et al. (2000) J, Cell. Biol. 148: 453 5) Rojo et al. (2003) Proc. Natl. Acad. Sci. USA 100: 7389
