CHANGES IN LIPID-COMPOSITION IN TOBACCO CELLS TREATED WITH CRYPTOGEIN, AN ELICITOR FROM PHYTOPHTHORA-CRYPTOGEA

Changes in lipid composition occurred when tobacco cells (Nicotiana ta bacum var. Xanthi) were treated with cryptogein, a proteinaceous elici tor from Phytophthora cryptogea. The most striking change was an incre ase in acylated steryl glycosides and steryl esters levels, certainly resulting from the glycosylation and/or esterification of free sterols . Moreover, in vivo pulse-labelling experiments with [C-14]acetate als o showed that a progressive decline in the incorporation rate of [C-14 ]acetate into free sterols started with the induction of sesquiterpeno id synthesis and lasted when sesquiterpenoid synthesis stops. This phe nomenon was accompanied by a significant increase in the synthesis rat e of phosphatidylethanolamine occuring after a period of 12 h (80% of [C-14]incorporated into lipids was found in PE). These pulse-labelling experiments also indicated a transient neosynthesis of high levels of acylated steryl glycosides and steryl esters in elicited cells. These results demonstrated that glycosylation and/or esterification of ster ols (preexistent or neosynthetised) is an initial event among plant ce ll responses associated with the hypersensitive reaction.