CDNA SEQUENCE OF A SUNFLOWER OLEOSIN AND TRANSCRIPT TISSUE-SPECIFICITY

Oleosins (oil body membrane proteins) of 20.5 and 18 kDa have been purified from sunflower (Helianthus annuus) seeds and polyclonal antibodies raised against them. The precipitated rabbit immunoglobulin fraction was purified by affinity chromatography on cyanogen bromide-activated Sepharose and specifically recognised polypeptides of 18 and 20.5 kDa in sunflower homogenate and oil body fractions assayed by western blotting. A near-full-length cDNA clone was isolated for the 20.5 kDa oleosin. The 694 bp cDNA contained an open reading frame of 534 bp, followed by an untranslated region of 81 bp and a poly(A) region of 70 bp. The open reading frame encoded a polypeptide of 19.8 kDa. Study of transcript localisation revealed message to be abundant in the embryo during the later stage of development and still present in the dry seed. No signal was observed in RNA prepared from expanding leaves.