ND7 gene involved in the membrane fusion in regulated exocytosis is conserved in three species of Paramecium

Abstract

A Paramecium tetraurelia ND7 gene homolog was cloned and sequenced in P. caudatum. The predicted protein possessed well-conserved regions, a transmembrane helix and two coiled-coil domains possibly involved in protein-protein interaction, as previously suggested for P. tetraurelia. Southern hybridization revealed that the ND7 gene homolog was also present in P. multimicronucleatum, suggesting that the ND7p is well-conserved and plays an important role in regulated exocytosis in Paramecium species. We treated cells with lysozyme to discharge most of the trichocysts and incubated cells to regenerate them. The ND7 mRNA was present only in a trace amount in cells with abundant trichocysts, while, it drastically increased in trichocyst-regenerating cells. This work also provides a useful system to isolate genes/proteins which are involved in trichocyst discharge in Paramecium.