@article{3e961c9dda84445e817362415109f670,
title = "Comparison of gene expression of Paramecium bursaria with and without Chlorella variabilis symbionts",
abstract = "Background: The ciliate Paramecium bursaria harbors several hundred cells of the green-alga Chlorella sp. in their cytoplasm. Irrespective of the mutual relation between P. bursaria and the symbiotic algae, both cells retain the ability to grow without the partner. They can easily reestablish endosymbiosis when put in contact with each other. Consequently, P. bursaria is an excellent model for studying cell-cell interaction and the evolution of eukaryotic cells through secondary endosymbiosis between different protists. Despite the importance of this organism, no genomic resources have been identified for P. bursaria to date. This investigation compared gene expressions through RNA-Seq analysis and de novo transcriptome assembly of symbiont-free and symbiont-bearing host cells.Results: To expedite the process of gene discovery related to the endosymbiosis, we have undertaken Illumina deep sequencing of mRNAs prepared from symbiont-bearing and symbiont-free P. bursaria cells. We assembled the reads de novo to build the transcriptome. Sequencing using Illumina HiSeq2000 platform yielded 232.3 million paired-end sequence reads. Clean reads filtered from the raw reads were assembled into 68,175 contig sequences. Of these, 10,557 representative sequences were retained after removing Chlorella sequences and lowly expressed sequences. Nearly 90% of these transcript sequences were annotated by similarity search against protein databases. We identified differentially expressed genes in the symbiont-bearing P. bursaria cells relative to the symbiont-free cells, including heat shock 70 kDa protein and glutathione S-transferase.Conclusions: This is the first reported comprehensive sequence resource of Paramecium - Chlorella endosymbiosis. Results provide some keys for the elucidation of secondary endosymbiosis in P. bursaria. We identified P. bursaria genes that are differentially expressed in symbiont-bearing and symbiont-free conditions.",
keywords = "Chlorella variabilis, Paramecium bursaria, Secondary symbiosis, Transcriptome analysis",
author = "Yuuki Kodama and Haruo Suzuki and Hideo Dohra and Manabu Sugii and Tatsuya Kitazume and Katsushi Yamaguchi and Shuji Shigenobu and Masahiro Fujishima",
note = "Funding Information: Symbiont-free P. bursaria strain Yad1w was produced from Chlorella sp.-bearing P. bursaria strain Yad1g cells (syngen 3, mating type I) through repeated cloning and cultivation under dark conditions. The Yad1g cell strain was collected in Yamaguchi, Japan in 2004. Symbiont-bearing strain of Yad1g1N cells was used for symbiont-bearing cells. The Yad1g1N strain was produced by infection of cloned symbiotic Chlorella variabilis (formerly C. vulgaris) strain 1 N cells to the Yad1w cell [15]. Paramecium strains used for this study were provided by Symbiosis Laboratory, Yamaguchi University with support in part by the National Bio-Resource Project of the Ministry of Education, Culture, Sports, Science and Technology, Japan. The culture medium used was 1.25% (w/v) fresh lettuce juice in modified Dryl{\textquoteright}s solution (MDS) [43] (KH2PO4 was used instead of NaH2PO4 ·2H2O), inoculated with a non-pathogenic strain of Klebsiella pneumoniae one day before use [44]. In ordinary cultures, several hundred cells were inoculated into 2 ml culture medium. Then 2 ml of fresh culture medium was added on each of the next 12 days. One day after the final feeding, the cultures were in the early stationary phase of growth. All cells used in the present experiments were at this phase. Cultivation and all experiments were performed at 25 ± 1°C. In the case of the symbiont-bearing strain of Yad1g1N, the cells were cultivated under constant light conditions: 20–30 μmol photon/m2/s. Funding Information: We thank Dr. Motohide Aoki, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, for his kind technical assistance in isolation of Chlorella RNAs. This work was supported by a Grant-in-Aid for Research Activity Start-up (No. 22870023) and by a Grant-in-Aid for Young Scientists (B) from the Japan Society for the Promotion of Science (JSPS), by a grant from the Inoue Foundation for Science (Inoue Research Award for Young Scientists), by a Narishige Zoological Science Award, and by a Grant for Basic Science Research Projects from The Sumitomo Foundation to Y. Kodama. This work was also supported by a Grant-in-Aid for Scientific Research (B) (No. 22370082) and a Grant-in-Aid for Challenging Exploratory Research (No. 23657157) from JSPS to M. Fujishima.",
year = "2014",
month = mar,
day = "10",
doi = "10.1186/1471-2164-15-183",
language = "English",
volume = "15",
journal = "BMC Genomics",
issn = "1471-2164",
publisher = "BioMed Central",
number = "1",
}