ACCUMULATION OF JASMONATE, ABSCISIC-ACID, SPECIFIC TRANSCRIPTS AND PROTEINS IN OSMOTICALLY STRESSED BARLEY LEAF SEGMENTS

The accumulation of abundant proteins and their respective transcripts , induced by 10(-4) M cis-abscisic acid or 10(-5) M jasmonic acid meth yl ester, was studied in barley (Hordeum vulgare L.) leaf segments and compared to that resulting from osmotic stress caused by floating the segments on solutions of sorbitol, glucose, polyethyleneglycol (PEG)- 6000 or NaCl. Osmotic stress or treatment with abscisic acid led to th e synthesis of novel proteins which were identical to jasmonate-induce d proteins (JIPs) with respect to immunological properties and molecul ar masses. The most prominent polypeptides were characterized by molec ular masses of 66,37 and 23 kDa and were newly synthesized. Whereas so rbitol, mannitol, sucrose, glucose and PEG provoked the synthesis of J IPs, 2-deoxyglucose and NaCl did not. We provide evidence that the syn thesis of JIPs induced by osmotic stress is directly correlated with a preceding rise in endogenous jasmonates. These jasmonates, quantified by an enzyme immunoassay specific for (-)-jasmonic acid and its amino -acid conjugates, increased remarkably in leaf segments treated with s orbitol, glucose or other sugars. In contrast, no increase in jasmonat es could be observed in tissues exposed to salts (NaCl). The results s trengthen the hypothesis that the accumulation of jasmonates, probably by de-novo synthesis, is an intermediate and essential step in a sign alling pathway between (osmotic) stress and activation of genes coding for polypeptides of high abundance.