ETHYLENE-INDUCED INCREASE IN GLUTAMINE-SYNTHETASE ACTIVITY AND MESSENGER-RNA LEVELS IN HEVEA-BRASILIENSIS LATEX CELLS

Ethylene, used as a stimulant of latex production in Hevea brasiliensi s, significantly activates the regenerating metabolism within the lati ciferous cells. In this context, attention was focused on glutamine sy nthetase (GS; EC 6.3.1.2), a key enzyme in nitrogen metabolism. A spec ific and significant activation of the cytosolic glutamine synthetase (GS(cyt)) in the laticiferous cells after ethylene treatment parallels the increase of latex yield. A marked accumulation of the correspondi ng mRNA was found, but in contrast, a slight and variable increase of the polypeptide level is at the limit of detection by western blotting . The GS response to ethylene might be mediated by ammonia that increa ses in latex cytosol following ethylene treatment. The physiological s ignificance for such a regulation by ethylene of the GS(cyt) is discus sed in terms of the nitrogen requirement for protein synthesis associa ted with latex regeneration.