INDUCTION OF A GENE ENCODING AN OLEOSIN HOMOLOG IN CULTURED CITRUS CELLS EXPOSED TO SALT STRESS

A cDNA clone (C3) with high homology to plant oleosins was isolated fr om citrus cultured cells. The 827-bp cDNA insert has an open reading f rame of 144 amino-acid residues. The central hydrophobic domain of the protein is nearly identical to oleosins from Brassica napus and maize , and the C-terminal hydrophilic region following the hydrophobic doma in is also highly conserved. The steady-state level of mRNA hybridizin g to C3 was significantly increased upon exposure of citrus cells to 0 .2 M NaCl. A lower level of transcript was found in seeds, but none co uld be detected in any other vegetative tissue (leaves, roots or fruit ) even in the presence of salt under the conditions used. The inductio n of the oleosin homologue in citrus cells by salt does not depend on the developmental stage of the cells.