Comparative analysis of zygospore transcripts during early germination in Chlamydomonas reinhardtii |
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Authors: | Hiroaki Aoyama Seikoh Saitoh Tsuneyoshi Kuroiwa Soichi Nakamura |
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Affiliation: | 1. Center of Molecular Biosciences, Tropical Biosphere Research Center, University of the Ryukyus, Nishihara, Okinawa 903-0213;2. Initiative Research Unit, College of Science, Rikkyo University, Nishi-Ikebukuro, Tokyo, 171-8501;3. Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213 |
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Abstract: | The unicellular green alga Chlamydomonas reinhardtii has a haplontic life cycle, and forms diploid zygotes for reproduction. The zygospore, a sporulating zygote, begins germination in response to light signals, generating haploid progenies and inducing several cell-biological events; e.g., DNA synthesis and meiotic division, successively. Their regulatory mechanisms remain largely unknown, so we focused on the early stages of germination and analyzed the dynamics of gene expression associated with the germination process. The gene expression levels of zygospores at 1 and 6 h after light exposure were analyzed by a next-generation sequencing platform, the 454 GS Junior. At 6 h, the photosynthesis pathway, including its antenna proteins and two methionine metabolism-related genes (methionine synthase and sulfite reductase), were up-regulated compared to 1 h after light exposure. Meanwhile, three uncharacterized genes that contained an antibiotic biosynthesis monooxygenase domain and an HSP20/alpha crystallin family protein were specifically expressed at 1 h after light exposure. These gene expressions were also verified by quantitative real-time PCR analysis. These results suggest that the photosynthesis and methionine synthesis pathways, both of which occur in the chloroplast, are activated in zygospores at around 6 h after light exposure, and that some polyketides and/or a small heat shock protein may be related to the initiation of zygospore germination. |
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Keywords: | ABM, antibiotic biosynthesis monooxygenase CBLP, guanine nucleotide-binding-like protein β-subunit FDR, false-discovery rate FPKM, fragments per kilobase of exon per million fragments mapped GO, Gene ontology GSEA, Gene-set enrichment analysis HSP20, Hsp20/alpha crystallin family HSP22G, heat shock protein 22G KO, KEGG Orthology KS score, Kolmogorov&ndash Smirnov style statistic LHCA1, light-harvesting complex I chlorophyll a/b binding protein 1 LHCB5, light-harvesting complex II chlorophyll a/b binding protein MAA7, tryptophan synthase beta subunit MS, methionine synthase NGS, next-generation sequencing psaA, Photosystems I and II PSI P700 apoprotein A1 psbA, photosystem II protein D1 qRT-PCR, quantitative real-time PCR RPL35, ribosomal protein L35 SAM, S-adenosylmethionine sHSP, small heat shock protein SIR, sulfite reductase TAP, Tris-acetate-phosphate. |
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