The secretory nature of the lesion of carrot cell variant ts11, rescuable by endochitinase

The carrot cell variant ts11 is unable to form somatic embryos at the non-permissive temperature of 32 °C, but the block can be overcome by the addition of a 32-kDa acidic endochitinase to the medium. In this work we conducted a cyto-histological analysis of the blocked embryo forms. The morphology...

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Bibliographic Details
Published in:Planta 1997, Vol.203 (3), p.381-389
Main Authors: Baldan, Barbara, Guzzo, Flavia, Filippini, Francesco, Gasparian, Marine, LoSchiavo, Fiorella, Vitale, Alessandro, de Vries, Sacco C., Mariani, Paola, Terzi, Mario
Format: Article
Language:English
Subjects:
Biological and medical sciences
Biotechnology
Cell biochemistry
Cell lines
Cell membranes
Cell physiology
Cell walls
Cells, Cultured
Chitinases - metabolism
Chitinases - pharmacology
Cultured cells
Daucus carota - genetics
Daucus carota - physiology
Daucus carota - ultrastructure
Embryos
Fundamental and applied biological sciences. Psychology
Genetic Variation
Membrane and intracellular transports
Microscopy, Electron
Molecular and cellular biology
Plant physiology and development
Plants
Polysaccharides
Proteins
Secretion
Secretory cells
Seeds - physiology
Seeds - ultrastructure
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Summary:The carrot cell variant ts11 is unable to form somatic embryos at the non-permissive temperature of 32 °C, but the block can be overcome by the addition of a 32-kDa acidic endochitinase to the medium. In this work we conducted a cyto-histological analysis of the blocked embryo forms. The morphology of the endomembrane system is altered; in particular, the ER is dilated and may show electron-dense precipitates and continuity with the plasma membrane. These morphological alterations do not occur in the presence of externally-added endochitinase. We also noticed modifications of the culture medium that are probably related to the morphological observations: the total amount of secreted proteins is reduced and pulse-chase experiments revealed that, compared with wild-type cells, the secretion of major polypeptides is reduced while new minor polypeptides are secreted. Western blot analysis revealed the presence of the binding protein BiP, a resident of the ER and of glutamine synthase, a cytosolic protein, in the medium of ts11 but not wild-type cells. These results indicate that ts11 is altered in the secretory pathway but do not clarify the role of endochitinase.
ISSN:0032-0935
1432-2048
DOI:10.1007/s004250050204