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

• 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
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s004250050204

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.