A Major Jasmonate-Inducible Protein of Sweet Potato, Ipomoelin, is an ABA-Independent Wound-Inducible Protein

Treatment of sweet potato plants cultured in vitro with a vaporof methyl jasmonate (MeJA) induced an accumulation in leavesof a large amount of protein with an apparent molecular massof 18 kDa. This protein, designated ipomoelin, was purified,and the amino acid sequences of proteolytic fragments were determined.Screening a cDNA library of MeJA-treated leaves by oligonucleotideprobes designed from the peptide sequences identified a clonethat could code for a polypeptide with 154 amino acids. Thededuced amino acid sequence of ipomoelin showed an overall aminoacid identity of 25% with the salt-inducible SalT protein ofrice. In addition, the C-terminal 70 amino acid sequence ofipomoelin showed about 50% identity with the C-terminal aminoacid sequences of seed lectins from Moraceae. The gene for ipomoelinwas present in a few copies in the genome of sweet potato. ThemRNA for ipomoelin was detected in leaves and petioles, butnot in stems and tuberous roots, of sweet potato plants grownin the field. Mechanical wounding of leaves induced ipomoelinmRNA both locally and systemically, while treatment of leaveswith ABA, salt, or a high level of sucrose did not induce ipomoelinmRNA. By contrast, ABA-inducible mRNA for sporamin was not inducedby MeJA. These results suggest that ipomoelin is involved indefensive reactions of leaves in response to wounding and thatJA-mediated wound-induction of ipomoelin occurs independentlyof ABA. (Received January 6, 1997; Accepted March 13, 1997)