The targeting and accumulation of ectopically expressed oleosin in non-seed tissues of Arabidopsis thaliana

Full-length and N-terminal deletions of a sunflower (Helianthus annuus L.) oleosin protein were expressed ectopically in transgenic Arabidopsis thalia na (L.) Heynh. Immunological detection of the sunflower protein revealed th at it accumulated in a range of non-oil-storing tissues, including leaves, roots and petals. This accumulation was shown to result from deposition in the microsomal membrane fraction. Expression in oil-storing tissues (such a s seeds) of oleosin N-terminal deletions revealed impaired transfer from th e endoplasmic reticulum to the oil body. In non-oil-storing tissues, accumu lation in the microsomal membrane fraction was progressively reduced by N-t erminal deletion. These data confirm the role of the endomembrane system in the targeting of the oleosin and its intimate relationship with oil-body b iogenesis.