THE IDENTIFICATION OF LEAF THIONIN AS ONE OF THE MAIN JASMONATE-INDUCED PROTEINS OF BARLEY (HORDEUM-VULGARE)

Jasmonic acid (JA) and its methyl ester (JA-Me) are able to introduce the accumulation of several specific polypeptides in cut leaf segments of barley. Two of the most prominent JA-induced proteins of M(r) 15000 and 23 000 have been characterized by isolating and sequencing complete cDNA sequences. While the sequence of the M(r)23 000 polypeptide shows no similarity to published sequences, the sequence of the M(r)15 000 polypeptide corresponds to the higher-molecular-weight precursor of a leaf thionin previously characterized. Transcripts for the M(r)23 000 and M(r)15 000 polypeptides accumulate in leaf segments shortly after the beginning of JA treatment. JA and JA-Me induce the appearance of the two proteins not only in leaf segments but also in intact barley seedlings. However, in seedlings the accumulation of JA-induced proteins occurs much more slowly and requires high concentrations of volatile JA-Me. Thus, in barley it seems unlikely that volatile JA-Me is involved in the interaction between different members of this species, as has been proposed recently for tomato seedlings.