LIPID AND PROTEIN-CHANGES IN JOJOBA CALLUS UNDER SALT STRESS

Calluses of jojoba [Simmondsia chinensis (Link) Schneider] were grown for two months in medium either without salt (control), or with 150 mM NaCl (treated). During the first month, the salt-treated calluses grew much more slowly than the controls, and most of them (60%) became necrotic. Afterwards, the salt-resistant calluses grew faster for one more month. Their morphological aspect was similar to that of the controls but their cells appeared enlarged and with thicker walls. Polypeptides of 18, 27 and 49 kDa, which accumulated in salt-treated calluses, appeared as marker proteins for salt adaptation. In contrast 24 and 75 kDa polypeptides, which accumulated with time in both control and treated calluses, could be considered as age marker proteins. The digalactosyldiacylglycerol content decreased in salt-treated calluses. In contrast the amount of monoplactosyldiacylglycerol dropped under ageing in both control and treated calli, with parallel triacylglycerol accumulation. Old salt-treated calluses contained more unsaturated polar lipids than the controls with higher percentage of linoleic acid in phosholipids and linolenic acid in galactolipids. An additionnal effect of ageing and salt stress might concern the breakdown of galactolipids and synthesis of triacylglycerol, resulting from the activation of galactosyl hydrolases.