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 degrees 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.
Baldan
B
B
Dipartimento di Biologiá, Università, Padova, Italy.
Guzzo
F
F
Filippini
F
F
Gasparian
M
M
LoSchiavo
F
F
Vitale
A
A
de Vries
S C
SC
Mariani
P
P
Terzi
M
M
D002478:Cells, Cultured; D002688:Chitinases / Q000378:metabolism* / Q000494:pharmacology; D018552:Daucus carota / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D014644:Genetic Variation; D008854:Microscopy, Electron; D012639:Seeds / Q000502:physiology / Q000648:ultrastructure*
D002688:Chitinases