Jasmonate-induced alteration of gene expression in barley leaf segments analyzed by in-vivo and in-vitro protein synthesis

Abstract

Jasmonic-acid methylester promotes barley leaf senescence without changing the average synthesizing capacity for bulk leaf proteins in the treated tissues. This protein balance is the result of a massive formation of jasmonate-induced proteins (JIPs), which cannot be detected in controls (water-treated leaf segments). Jasmonate-induced proteins synthesized in vivo are virtually identical to the respective polypeptides translated in a wheat-germ system if programmed with the RNA of jasmonate-treated leaf segments. Both in-vivo-and in-vitro-formed JIPs correspond with molecular sizes of Mr 110, 66, 30, 23 and 10/12 kilodaltons. This observation indicates little if any post-translational modification. Specific mRNAs for JIPs and the JIPs labeled in vivo can be detected 3-5 h after jasmonate addition. Synthesis of JIPs increases up to 24 h whereas, at the same time, the translatable mRNAs for normal leaf proteins decrease drastically. This massive alteration of gene expression is reminiscent of heat-shock or other stress responses, but the proteins induced by jasmonate differ from those induced by elevated temperature with respect to molecular size, immunological relatedness, and kinetics of synthesis. It is suggested that JIP synthesis is rather a cause than a consequence of the common senescence symptoms and thus could represent some kind of early "stress" response in senescence induced by jasmonic-acid methylester. The action of jasmonic-acid methylester in gene expression points to a control at the transcript level.