Ethylene modulates gene expression in cells of the marine sponge Suberitesdomuncula and reduces the degree of apoptosis

Sponges (phylum Porifera) live in an aqueous milieu that contains dissolved organic carbon. This is degraded photochemically by ultraviolet radiation to alkenes, particularly to ethylene. This study demonstrates that sponge c ells (here the demosponge Suberites domuncula has been used), which have as sembled to primmorphs, react to 5 mu M ethylene with a significant up-regul ation of intracellular Ca2+ concentration and with a reduction of starvatio n-induced apoptosis, In primmorphs from S. domuncula the expression of two genes is up-regulated after exposure to ethylene. The cDNA of the first gen e (SDERR) isolated from S. domuncula encodes a potential ethylene-responsiv e protein, termed ERR_SUBDO; its putative M-r is 32,704. Data bank, search revealed that the sponge polypeptide shares high similarity (82% on amino a cid level) with the corresponding plant molecule, the ethylene-inducible pr otein from Hevea brasiliensis. Until now no other metazoan ethylene-respons ive proteins have been identified. The second gene, whose expression is up- regulated in response to ethylene is a Ca2+/calmodulin-dependent protein ki nase II. Its cDNA, SDCCdPK; encodes a M-r 54,863 putative kinase that share s 69% similarity with the corresponding enzyme from Drosophila melanogaster . The expression of both genes in primmorphs from S. domuncula is increased by approximate to 5-fold after a 3-day incubation period with ethylene, It is concluded that also metazoan cells, with sponge cells as at model, may react to ethylene with an activation of cell metabolism including gene indu ction.