ABSTRACT: A genome wide microarray platform containing the predicted coding sequences (putative genes) for the ciliated protozoan Tetrahymena thermophila is described, validated and used to study gene expression in growing, starved and conjugating cells. Of the ~27,400 predicted open reading frames in Tetrahymena, transcripts homologous to 5876 are not detectable in one or more of these life cycle stages, indicating that this organism does indeed contain a large number of functional genes. Transcripts from over 5000 predicted genes are expressed at levels 5X background and 95 genes are expressed at 250X background in all stages. Transcripts homologous to 94 predicted genes are specifically expressed and 155 more are highly up-regulated in growing cells, and 90 are specifically expressed and 616 are up-regulated during starvation. Strikingly, transcripts homologous to 1073 predicted genes are specifically expressed and 1753 are significantly up-regulated during conjugation. The patterns of gene expression during conjugation correlate well with the previously described developmental stages of meiosis, nuclear differentiation and DNA elimination. Genes encoding proteins known to be complexed show similar expression patterns, indicating that co-ordinate expression with putative genes of known function should identify new genes with related functions. Keywords: growth (three cell densities); Starvation (seven time points); Conjugation (ten time points) For growth, CU428 cells at low, medium and high cell densities (~100Kcells/ml, ~350Kcells/ml and ~1000Kcells/ml; referred to as L-l, L-m and L-h) were collected. For starvation, CU428 cells were starved at 2x105 cells/ml in 10 mM Tris (pH 7.5) for 3, 6, 9, 12, 15 and 24 hours ï¼referred to as S-0, S-3, S-6, S-9, S-12, S-15 and S-24. For conjugation, B2086 and CU428 cells that had been starved for 18 hours were resuspended in 10 mM Tris (pH 7.5) at 2x105 cells/ml, mixed, and samples were collected at 2, 4, 6, 8, 10, 12, 14, 16, 18 hours after the mixture ï¼referred to as C-0, C-2, C-4, C-6, C-8, C-10, C-12, C-14, C-16 and C-18). For each growing and starved Tetrahymena sample, hybridizations were performed on three independent microarrays (e.g. L1, L2 and L3; S1, S2 and S3). For analysis of conjugation, hybridizations were performed on two independent microarrays (e.g. C1 and C2). Each individual microarray represents a separate experiment; total RNA was isolated from independent cell cultures then independently labeled and hybridized.
