(-) – jasmonic acid and it methyl esters are ubiquitous in plants. They have hormone properties, help regulating plant growth and development and they seem to participate in leaf senescence and in the defence mechanism against fungi.
Just like all other plant hormones have jasmonates both activating and inhibiting effects. Synergistic and antagonistic effects on other hormones have been observed, too. Jasmonate derivatives induce the accumulation of so-called jasmonate-induced-proteins that were found in all plant species tested. Their accumulation can also be caused by desiccation or ABA effects. Jasmonate-induced-proteins are of varying molecular weights, and molecules of different size classes have immunologically been shown to be related. The major portion of these proteins is not glycosylated, has no proteolytic activity and is metabolically stable. Labelling with immunogold and electron microscopy showed that some of them are located within the nucleus, while others were detected in the vacuole. None have ever been found in mitochondria. Their synthesis can be inhibited by cycloheximid, but not by chloramphenicol. Chloramphenicol affects mitochondrial proteins. Jasmonate-induced-proteins are lacking in roots, in bleached leaves, and in leaves of chlorophyll-deficient Hordeum vulgare mutants. They exist in etiolated leaves, though. Jasmonates do not only regulate the transcription of these proteins, they do also influence the rate of translation of different groups of mRNA. They do, for example, decrease the production rate of several essential housekeeping proteins.
Just like ABA inhibit jasmonates a premature germination of the oil-containing seeds of Brassica and Linum. After germination do they induce the synthesis of the seed storage proteins Napin and Cruciferin as well as that of several more elaiosome-associated proteins (PARTHIER, 1991). (PARTHIER, 1991).
© Peter v. Sengbusch - b-online@botanik.uni-hamburg.de
