NATIONAL INSITUTE FOR BASIC BIOLOGY  


National Institute for Basic Biology

DIVISION OF SPECIATION MECHANISMS II


Professor:
Ken-ichirou Morohashi
Associate Professor:
Mitsuyasu Hasebe
Reserch Associate:
Satoru Ishihara
Technical Staff:
Sanae Oka
Post Doctral Fellow:
Naoe Kotomura 4
Satomi Shindo
Kumi Aso (Univ. of Tokyo)
Ken Kawabe (Kyushu Univ.)
Tokuo Mukai (Kyushu Univ.)
Mikihiko Kato (Nagoya Univ.)
Hirofumi Mizusaki (Kumamoto Univ.)
Tomoaki Nishiyama (Univ. of Tokyo)
Keiko Sakakibara (Univ. of Tokyo)
Ryosuke Sano (Chiba Univ.)
Tatsuji Shikayama (Kyushu Univ.)
Kazuyoshi Someya (Univ. of Tokyo)
Hayato Yokoi (Nagoya Univ.)
Visiting Fellow:
Rumiko Kofuji
Yoshiyuki Kojima
Assistant:
Hisae Tsuboi


This division was established recently with two research groups. These two groups managed by the professor, Ken-ichirou Morohashi (I), and the associate professor, Mitsuyasu Hasebe (II), have adopted animals and plants, respectively, as the materials for the research. Our attention has been and will be directed to understanding mechanisms underlying differentiation of the reproductive system of animals and evolution of the morphology in plants. These efforts with a variety of the materials are expected to give us deeper insights into speciation mechanisms of organism.



I. Reproduction of animals.

Because of the fundamental and pivotal function of the gonads, extensive efforts have been made to characterize the differentiation processes including sex-dependent differentiation. By focusing on the steroidogenesis as one of the gonad specific functions, we identified a steroidogenic tissue specific transcription factor designated Ad4BP/SF-1. Recent studies with an antiserum to Ad4BP/SF-1 and a gene disrupted mice clearly demonstrated that the transcription factor is essential for differentiation of the steroidogenic tissues, the gonads and the adrenal cortex. Showing a good correlation with the observation above, a particular cell population identified as Ad4BP/SF-1 immunoreactive cells (AGP, adreno-genital primordium) was revealed to give rise to these distinct tissues. These observations gave us many interesting issues as follows. What is the signal for the onset of the Ad4BP/SF-1 gene transcription in the particular cells, AGP? What is the mechanism underlying the separation of the AGP into the adrenal and gonadal primordia? How is the mechanism employed for sex differentiation of the gonads? Why dose such sex dependent differentiation not occur in the adrenal cortex? To address these issues, functions and regulation of nuclear transcription factors, WT1, SRY, SOX9, and DAX1 as well as Ad4BP/SF-1, all of which are critically implicated in gonadal and adrenocortical differentiation, have been investigated from the molecular and morphological aspects.



II. Morphological Evolution in plants.

Morphological diversity among taxa is the most prominent characteristics in the biodiversity. Our group aims to explore genetical and molecular changes which caused renovative morphological changes during the course of land plants evolution. We selected Arabidopsis (angiosperm), Gnetum (gymnosperm), Ginkgo (gymnosperm), Ceratopteris (pteridophyte), Physcomitrella (bryophyte), and Chlamydomonas (green algae) as model plants to compare the genes related to morphogenesis. We are focusing on the following three topics; (1) Evolution of floral homeotic genes (MADS gene family and LEAFY gene homologue which is a regulator of the MADS genes), (2) Comparison of homeobox gene functions between sporophyte and gametophyte generations to reveal the evolution of the both generations, and (3) establishment of mutant library of Physcomitrella patens to get new morphological mutants which have not been obtained from the study of the higher plants having only reduced gametophytic generations. Some MADS, LEAFY and homeobox genes have been cloned from the gymnosperms, Ceratopteris, Physcomitrella and the analyses of their functions are in progress. Comparisons of the gene functions and swapping experiments of genes among the organisms will make possible to infer what kinds of changes of developmental genes caused morphological diversity of oragnisms.



Publication List:
S. Leers-Sucheta, K. Morohashi, J. I. Mason, & M. H. Melner. (1997) Synergistic Activation of the Human Type II 3b-Hydroxysteroid Dehydrogenase/D5D4 Isomerase Promoter by the Transcription Factor Steroidogenic Factor-1/Adrenal 4-Binding Protein and Phorbol Ester. J. Biol.Chem. 272, 7960-7967.
J. Lund, M. Bakke, G. Mellgren, K. Morohashi, & S.-O. Doskeland. (1997) Trnascriptional regulation of the bovine CYP17 gene by cAMP. Steroid 62, 43-45.
J. I. Mason, D. Keeney, I. M. Bird, W. E. Rainey, K. Morohashi, S. Leers-Sucheta, & M. H. Melner. (1997) The regulation of 3b-hydroxysteroid dehydrogenase expression. Steroid 62, 164-168.
K. Morohashi. (1997) The ontogenesis of the steroidogenic tissues. Genes Cells 2, 95-106.
Hasebe, M. (1997) Molecular phylogeny of Ginkgo biloba. In T. Hori, ed., Ginkgo biloba (Springer-Verlag), pp173-181.
Hasebe, M. and Banks, J.A. (1997) Evolution of MADS gene family in plants. In K. Iwatsuki and P.H. Raven eds., Evolution and Diversification in Land Plants (Springer-Verlag), pp179-197.
Fukada-Tanaka, S., Hoshino, A., Hisatomi, Y., Habu, Y., Hasebe, M. and Iida, S. (1997) Identification of new chalcone synthase genes for flowerpigmentation in the Japanese and common morning glories. Plant Cell Physiol. 38: 754-758.



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Last Modified: 12:00, May 28, 1998