@article {1766, title = {Triploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex.}, journal = {Chromosoma}, volume = {123}, year = {2014}, month = {2014 Jun}, pages = {265-72}, abstract = {

Although polyploids are common among plants and some animals, polyploidization often causes reproductive failure. Triploids, in particular, are characterized by the problems of chromosomal pairing and segregation during meiosis, which may cause aneuploid gametes and results in sterility. Thus, they are generally considered to reproduce only asexually. In the case of the Platyhelminthes Dugesia ryukyuensis, populations with triploid karyotypes are normally found in nature as both fissiparous and oviparous triploids. Fissiparous triploids can also be experimentally sexualized if they are fed sexual planarians, developing both gonads and other reproductive organs. Fully sexualized worms begin reproducing by copulation rather than fission. In this study, we examined the genotypes of the offspring obtained by breeding sexualized triploids and found that the offspring inherited genes from both parents, i.e., they reproduced truly bisexually. Furthermore, meiotic chromosome behavior in triploid sexualized planarians differed significantly between male and female germ lines, in that female germ line cells remained triploid until prophase I, whereas male germ line cells appeared to become diploid before entry into meiosis. Oocytes at the late diplotene stage contained not only paired bivalents but also unpaired univalents that were suggested to produce diploid eggs if they remained in subsequent processes. Triploid planarians may therefore form euploid gametes by different meiotic systems in female and male germ lines and thus are be able to reproduce sexually in contrast to many other triploid organisms.

}, keywords = {Animals, Chromosomes, Female, Germ Cells, Male, Meiosis, planarians, reproduction, Triploidy}, issn = {1432-0886}, doi = {10.1007/s00412-013-0449-2}, author = {Chinone, Ayako and Nodono, Hanae and Matsumoto, Midori} } @article {1731, title = {The identification of ᴅ-tryptophan as a bioactive substance for postembryonic ovarian development in the planarian Dugesia ryukyuensis}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {2017/03/24/online}, pages = {45175 - }, publisher = {The Author(s)}, url = {http://dx.doi.org/10.1038/srep45175}, author = {Kobayashi, Kazuya and Maezawa, Takanobu and Tanaka, Hiroyuki and Onuki, Hiroyuki and Horiguchi, Yurie and Hirota, Hiroshi and Ishida, Tetsuo and Horiike, Kihachiro and Agata, Yasutoshi and Aoki, Manabu and Hoshi, Motonori and Matsumoto, Midori} } @article {669, title = {The Dugesia ryukyuensis database as a molecular resource for studying switching of the reproductive system}, journal = {Zoological Science}, volume = {24}, number = {1}, year = {2007}, month = {01/2007}, pages = {31-37}, publisher = {Zoological Society of Japan}, abstract = {

The planarian Dugesia ryukyuensis reproduces both asexually and sexually, and can switch from one mode of reproduction to the other. We recently developed a method for experimentally switching reproduction of the planarian from the asexual to the sexual mode. We constructed a cDNA library from sexualized D. ryukyuensis and sequenced and analyzed 8,988 expressed sequence tags (ESTs). The ESTs were analyzed and grouped into 3,077 non-redundant sequences, leaving 1,929 singletons that formed the basis of unigene sets. Fifty-six percent of the cDNAs analyzed shared similarity (E-value\<1E -20) with sequences deposited in NCBI. Highly redundant sequences encoded granulin and actin, which are expressed in the whole body, and other redundant sequences encoded a Vasa-like protein, which is known to be a component of germ-line cells and is expressed in the ovary, and Y-protein, which is expressed in the testis. The sexualized planarian expressed sequence tag database (http://planaria.bio.keio.ac.jp/planaria/) is an open-access, online resource providing access to sequence, classification, clustering, and annotation data. This database should constitute a powerful tool for analyzing sexualization in planarians.

}, doi = {http://dx.doi.org/10.2108/zsj.24.31}, url = {http://www.bioone.org/doi/abs/10.2108/zsj.24.31}, author = {Hideyuki Ishizuka and Takanobu Maezawa and Junpei Kawauchi and Hanae Nodono and Yukako Hirao and Osamu Nishimura and Haruka Nakagawa and Kiyono Sekii and Kenta Tasaka and Hiroshi Tarui and Kiyokazu Agata and Hoshi, Motonori and Kobayashi, Kazuya and Yasubumi Sakakibara and Matsumoto, Midori} } @article {springerlink:10.1007/s00412-008-0148-6, title = {Production of diploid and triploid offspring by inbreeding of the triploid planarian Dugesia ryukyuensis}, journal = {Chromosoma}, volume = {117}, year = {2008}, note = {10.1007/s00412-008-0148-6}, pages = {289-296}, publisher = {Springer Berlin / Heidelberg}, abstract = {

Triploidy has generally been considered to be an evolutionary dead end due to problems of chromosomal pairing and segregation during meiosis. Thus, the formation of tetraploids and diploids from triploid types is a rare phenomenon. In the present study, we demonstrated that inbreeding of the triploid planarian Dugesia ryukyuensis resulted in both diploid and triploid offspring in nature. In the triploids of D. ryukyuensis , chiasmata between homologous chromosomes were observed in both female and male germ lines. This result suggests that both diploid and triploid offspring of this species are produced bisexually by zygotic fusion between sperm and eggs. Hence, this phenomenon may be a novel mechanism in planarian for escaping the triploid state.

}, issn = {0009-5915}, url = {http://dx.doi.org/10.1007/s00412-008-0148-6}, author = {Kobayashi, Kazuya and Ishizu, Hirotsugu and Arioka, Sachiko and Padilla Cabrera, Jocelyn and Hoshi, Motonori and Matsumoto, Midori} } @article {729, title = {DrRad51 is required for chiasmata formation in meiosis in planarian Dugesia ryukyuensis}, journal = {Molecular Reproduction and Development}, year = {2014}, abstract = {

Rad51, a conserved eukaryotic protein, mediates the homologous-recombination repair of DNA double-strand breaks that occur during both mitosis and meiosis. During prophase I of meiosis, homologous recombination enhances the linkage between homologous chromosomes to increase the accuracy of segregation at anaphase I. In polyploidy situtations, however, difficulties with homologous chromosome segregation often disrupt meiosis. Yet, triploid individuals of the planarian Dugesia ryukyuensis are able to produce functional gametes through a specialized form of meiosis. To shed light on the molecular mechanisms that promote successful meiosis in triploid D. ryukyuensis, we investigated rad51 gene function. We isolated three genes of the Rad51 family, the Rad51 homolog Dr-rad51 and the Rad51 paralogs Dr-rad51B and Dr-rad51C. Dr-rad51 was expressed in germ-line and presumably in somatic stem cells, but was not necessary for the regeneration of somatic tissue. RNA-interference (RNAi) depletion of Dr-rad51 during sexualization did not affect chromosome behavior in zygotene oocytes, but did result in the loss of chiasmata at the diplotene stage. Thus, homologous recombination does not appear to be necessary for synapsis, but is needed for crossover and proper segregation in D. ryukyuensis.

}, doi = {10.1002/mrd.22308}, author = {Ayako Chinone and Matsumoto, Midori} } @article {727, title = {Planarian D-amino acid oxidase is involved in ovarian development during sexual induction}, journal = {Mechanisms of Development}, year = {2014}, url = {http://www.sciencedirect.com/science/article/pii/S0925477314000033}, author = {Takanobu Maezawa and Hiroyuki Tanaka and Haruka Nakagawa and Mizuki Ono and Manabu Aoki and Matsumoto, Midori and Tetsuo Ishida and Kihachiro Horiike and Kobayashi, Kazuya} }