Induction of a gene encoding an oleosin homologue in cultured citrus cells exposed to salt stress.

A cDNA clone (C3) with high homology to plant oleosins was isolated from citrus cultured cells. The 827-bp cDNA insert has an open reading frame 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 domain is also highly conserved. The steady-state level of mRNA hybridizing 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 could be detected in any other vegetative tissue (leaves, roots or fruit) even in the presence of salt under the conditions used. The induction of the oleosin homologue in citrus cells by salt does not depend on the developmental stage of the cells.