Differential accumulation of storage products in developing seeds and somatic cell cultures of Daucus carota L.

Abstract

The major oleosin proteins of 15 and 19 kDa and the major storage albumins of 20 and 28 kDa were purified to homogeneity from carrot seeds and antibodies raised against them. Anti-oleosin antibodies recognised similar sized proteins in total protein and oil body fractions from non-embryogenic and embryogenic carrot suspension cultures and from carrot somatic embryos. Both oleosins and oil bodies accumulated in all carrot cell and tissue types but reached much higher levels in high osmoticum (0.4 M sucrose or sorbitol) than in basal media. In contrast, there was no evidence of storage protein accumulation in any carrot cell or tissue cultures in vitro, even in the presence of high osmoticum or plant growth regulators. The carrot cultures in vitro did not accumulate the high levels of octadecenoic fatty acids found in seeds but rather accumulated an oil which was high in linoleic acid and whose fatty acid profile resembled that of the membrane lipids. Non-embryogenic carrot cell cultures accumulated very little starch, whereas high levels were found in embryogenic cell cultures. Starch levels declined to low levels during somatic embryo development to the torpedo stage. The differences in the regulation of accumulation of oleosins, storage albumins, triacylglycerols and starch in vitro and in planta in carrot cells and tissues are discussed.