Towards the identification of meiosis and nuclear reorganization genes in Paramecium: a chromosome-wide study.

Jacek Nowak1,2,6, Robert Gromadka2, Marek Juszczuk2, Maria Jerka-Dziadosz3, Kamila Maliszewska2, Marie-Hélene Mucchielli1,4,5,6, Jean-François Gout7, Olivier Arnaiz1,4,5,6, Nicolas Agier1,4,5,6, Thomas Tang1,6, Lawrence Aggerbeck1,4,5,6, Jean Cohen1,4,5,6, Hervé Delacroix1,4,5,6, Linda Sperling1,4,5,6, Christopher Herbert1,4,5,6, Marek Zagulski2, Mireille Bétermier1,4,5,6

1 CNRS FRE3144, Centre de Génétique Moléculaire, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette cedex, France 2 Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego Street, 5a, 02-106 Warsaw, Poland 3 M. Nencki Institute of Experimental Biology, Polish Academy of Sciences, Pasteur Street, 3, 02-093 Warsaw, Poland 4 University Paris 11, Département de Biologie, Orsay, F-91405 5 Université Pierre et Marie Curie – Paris 6, UFR des Sciences de la Vie, Paris, F-75005 6 CNRS FRC3115, Centre de Recherches de Gif-sur-Yvette, Gif-sur-Yvette, France 7 CNRS UMR5558, Laboratoire de Biométrie et Biologie Evolutive, Université de Lyon, 43 boulevard du 11 Novembre 1918, Villeurbanne, F-69622

To gain broader insight into which biological functions participate in the correct progression of sexual processes and in the formation of a functional new MAC, we started a genome-wide analysis of the transcriptome based on the available annotation of the P. tetraurelia MAC genome sequence. At the beginning of this study, we have analysed the transcription profile of 465 genes carried by the Megabase chromosome, which was the first macronuclear chromosome to be annotated manually. We used dedicated DNA microarrays to monitor gene transcription during vegetative growth and throughout autogamy and identified four major variable transcription patterns during sexual processes: an early and a late induction peak, one cluster of gradual induction and one strongly repressed cluster. We picked 15 induced genes for in vivo functional studies and knocked down their expression by RNA interference. Four genes turned out to be essential during vegetative growth and were not tested during autogamy. Two other genes were shown to encode differentially localized nuclear proteins and were found to be essential for the recovery of viable sexual progeny. For those two genes more advanced in-depth studies were initiated in order to reveal their possible function in macronuclear development.