MALATE AS ADDITIONAL SUBSTRATE FOR FATTY-ACID SYNTHESIS IN A C-4-PLANT TYPE DEVELOPED BY SALT STRESS FROM A C-3-PLANT TYPE MAIZE - A SCREENING FOR MALATE AS SUBSTRATE FOR FATTY-ACID SYNTHESIS IN CHLOROPLASTS

By changing a Zed mays variety (cv. Pirat) from a C-3-plant to a C-4-p lant type by salt stress with sodium chloride the capacity to form fat ty acids from malate was induced with the appearance of the NADP(+)-ma lic enzyme. The reaction catalyzed by the chloroplast pyruvate dehydro genase complex was the rate limiting step in the reaction sequence. Th is could be shown by comparing the rates of fatty acid formation from malate with those from pyruvate. However, the cytologically visible ch loroplast dimorphism in mesophyll and bundle-sheath eels was already d eveloped at the C-3-plant stage and persisted in the C-4-plant stage. On the other hand, the formation of fatty acids from malate in barley seedlings was very poor compared to that from acetate. Although the ac tivity of the chloroplast pyruvate dehydrogenase complex in this speci es was comparatively high (Preiss et al., 1993; Hoppe et al., 1993), t he activity of the NADP(+)-malic enzyme was negligible.