EXTRACELLULAR PROTEIN-PATTERNS OF GRAPEVINE CELL-SUSPENSIONS IN EMBRYOGENIC AND NONEMBRYOGENIC SITUATIONS

Somatic embryos produced from suspension cultures of grapevine rootstock 41B (Vitis vinifera cv. Chasselas x Vitis herlandieri) are blocked at the heart stage of development. Previous results have shown that extracellular macromolecules of molecular weight > 10 kDa, are likely involved in this inhibition (P. Coutos-Thevenot et al., Plant Cell Tiss. Org. Cult., 23 (1992) 125-133). The extracellular proteins and glycoproteins secreted by embryos differentiating in the absence of auxin have been compared to those secreted by undifferentiated cells growing in the presence of auxin. Specific proteins and glycoproteins (66, 62, 56, 51, 48, 36, 32, 25 and 10 kDa), under negative control of auxin, are secreted during embryogenesis. Thus, somatic embryogenesis in grapevine presents several similarities with the carrot model system as far as the influence of auxin on extracellular protein patterns and embryo differentiation is considered. This conclusion has been reinforced by showing that, as described in the carrot system, the 36-kDa glycoprotein excreted by grapevine embryos is a cationic peroxidase whereas the 10-kDa protein immunoreacts with an antibody directed against a maize lipid transfer protein. Study of extracellular protein patterns of a Chardonnay CH76 cell strain, strongly affected in its embryogenic response, showed significative differences in the excretion of some specific proteins compared to the 41B cell line.