The University of Tokyo · Energy
Professor Hisayoshi Nozaki's research lab focuses on the evolutionary biology and cellular biology of colonial green algae, particularly within the order Volvocales. The lab investigates the phylogenetic relationships, morphological diversification, and ultrastructural characteristics of these organisms, with an emphasis on understanding the evolutionary transitions leading to multicellularity and cellular differentiation. Using molecular phylogenetics, electron microscopy, and cladistic analyses, the lab explores the genetic and structural basis of colonial organization, reproductive strategies, and extracellular matrix architecture in species such as *Chlamydomonas*, *Pleodorina*, *Eudorina*, and *Pandorina*.
Figures are computed from collected data and may differ slightly.
By virtue of these attributes and others that we had discovered previously, C. merolae appears to have the simplest nuclear genome of the non-symbiotic eukaryotes. These unusually simple genomic features in the 100% complete genome sequence of C. merolae are extremely useful for further studies of eukaryotic cells.
ABSTRACT The chloroplast‐encoded large subunit of the ribulose‐1, 5‐bisphosphate carboxylase / oxygenase (rbcL) gene was sequenced from 20 species of the colonial Volvocales (the Volvacaceae, Goniaceae, and Tetrabaenaceae) in order to elucidate phylogenetic relationships within the colonial Volvocales. Eleven hundred twenty‐eight base pairs in the coding regions of the (rbcL) gene were analyzed by the neighbor‐joining (NJ) method using three kinds of distance estimations, as well as by the maxim
ABSTRACT A cladistic analysis was used to deduce the phylogenetic relationships within the colonial Volvocales. Forty‐one pairs of characters related to gross morphology and ultrastructure of vegetative colonies as well as asexual and sexual reproduction were analyzed based on parsimony, using the PAUP 3.0 computer program, for 25 species belonging to nine volvocacean and goniacean genera of the colonial Volvocales. Chlamydomonas reinhardtii Dangeard was the outgroup. The strict consensus tree i
The volvocacean genus Pleodorina has been morphologically characterized as having small somatic cells in spheroidal colonies and anisogamous sexual reproduction with sperm packets. In this study we examined two new species that can be assigned to the genus Pleodorina based on morphology: P. starrii H. Nozaki et al. sp. nov. and P. thompsonii F. D. Ott et al. sp. nov. P. starrii was collected from Japan and had 32‐ or 64‐celled colonies with anterior somatic cells and spheroidal individual cellul
Vegetative colonies of Pandorina unicocca Rayburn et Starr, four taxa of Eudorina [E. elegans Ehrenberg (type species), E. illinoisensis (Kofoid) Pascher, E. unicocca G.M. Smith var. unicocca andE. unicocca var. peripheralis Goldstein] and two species of Pleodorina [Po californicaShaw (type species) and P. indica (Iyengar) Nozaki] were examined with electron microscopy in order to characterize the structure of the extracellular matrix. Each cell of the colonies of all the taxa examined was tight
*Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan; Hayama Center for Advanced Studies, Graduate University for Advanced Studies, Kanagawa, Japan; The Institute of Statistical Mathematics, Tokyo, Japan; §Division of Life Science, Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo, Japan; and kDepartment of Evolutionary Studies of Biosystems, School of Advanced Sciences, Graduate University for Advanced Studies, Kanagawa, Japan
Based on phylogeny and morphological data, this novel genus exhibits a missing link between Platydorina and the typical spheroidal colonial volvocine members such as Pandorina or Yamagishiella. Considering the external obligate anisogamy, oogamy evolution may have been preceded by the transition from external to internal fertilization during anisogamy within the volvocine green algae.
The morphology, reproduction and taxonomy of Pleodorina japonica Nozaki sp. nov. collected in Japan were studied using clonal cultures. This taxon is distinguished from the other species of Pleodorina and Eudorina by its unique vegetative colonies, in which only 20–27% of the cells are somatic and anterior, and in which the gelatinous matrix does not form individual sheaths. Zygote germination was observed for the first time in Pleodorina. A single biflagellate gone-cell moved out from the zygot
The chloroplast‐encoded atp B gene was sequenced from 33 strains representing 28 species of the colonial Volvocales (the Volvocaceae and its relatives) to reexamine phylogenetic relationships as previously deduced by morphological data and rbc L gene sequence data.1128 base pairs in the coding regions of the atp B gene were analyzed by MP, NJ, and ML analyses. Although supported with relatively low bootstrap values (75% and 65% in the NJ and ML analyses, respectively), three anisogamous/oogamous
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