Differences in gene expression of the ciliate Paramecium caudatum caused by endonuclear symbiosis with Holospora obtusa, revealed using differential display reverse transcribed PCR.

We identified six genes of Paramecium caudatum, which differentially expressed in Holospora obtusa-bearing and H. obtusa-free cells using differential display reverse transcribed PCR (DDRT-PCR). Northern blot analyses revealed that two of the genes, CA10-3 and CA20-2, were expressed extensively in the H. obtusa-free cell, while the other four, AS16-1, CS14, CS21 and CA17-1, were expressed more in the H. obtusa-bearing cell. Putative amino acid sequences of CA10-3, AS16-1 and CA17-1 showed high homologies with known genes related to intracellular signaling, transcription and aerobic metabolism. CS14 and CS21 also showed homologies with some genes whose products are still functionally unknown, but CA20-2 encoded a novel protein. We show in this study that H. obtusa alters multiple gene expression of the host after establishing endosymbiosis.