ISOLATION, CHARACTERIZATION, AND CHROMOSOME MAPPING OF AN ACTIN GENE FROM THE PRIMITIVE GREEN ALGA, NANNOCHLORIS BACILLARIS (CHLOROPHYCEAE)

Abstract

Historically, the genus Nannochloris has been classified using the morphology of cell division, although the mechanics of division remain relatively poorly understood. Nannochloris bacillaris reproduces by binary fission. Microscopic observation with fluorescein isothiocyanate‐phalloidin showed that actin filaments localized near the nucleus and appeared as a ring‐ or beltlike structure in the septum‐forming area in the middle of the cell during cell division. In primitive unicellular Chlorophyta such as N. bacillaris, actin is also thought to play important roles in nuclear migration and cell division. The N. bacillaris actin gene has three exons and two introns defined by two exon–intron junctions with splice site consensus sequences. The two introns are located at codons specifying amino acids 3/4 and 47/48. One of these, intron position 3/4, is conserved in the actin gene of Saccharomyces cerevisiae. The actin gene product was predicted to be 378 amino acids long with an estimated molecular weight of 42 kDa. There is only one copy of the actin gene in the N. bacillaris genome. Nannochloris bacillaris has 14 chromosomes that range in size from 230 kb to 3000 kb, and the total size of the genome was estimated to be 20.3 Mb. The actin gene is on either chromosome XI or XII. In a phylogenetic tree based on the actin gene sequence, N. bacillaris diverged before the divergence of Volvox, Chlamydomonas, and higher plants, and very shortly after the radiation of the Rhodophyta.

Patterns of asexual reproduction in Nannochloris bacillaris and Marvania geminata (Chlorophyta, Trebouxiophyceae)

“…Nannochloris bacillaris NRJ was collected from Lake Nakatuna in Nagano Prefecture by Dr. N. Takamura of the National Institute for Environmental Studies at Tsukuba, Japan (Ogawa et al 1995;Arai et al 1998;Yamamoto et al 2001) and was given to us by Prof. K. Ueda of Nara Women's University (NRJ). M. coccoides CCAP251/1B was purchased from CCAP in 1998.…”

“…The nucleotide sequences of the actin genes from M. geminata SAG 12.88 and C. lobophora were used for phylogenetic analysis, along with the published sequences from N. bacillaris (Arai et al 1998), M. coccoides CCAP251/1B, N. eucaryotum KSW 0203 (a single colony was isolated from UTEX 2502, Yamamoto et al 2003), N. atomus SAG 14.87, N. sp. SAG 251-2., Picochlorum atomus CCAP251/ 7, P. kessleri IAM C-531 (Yamamoto et al 2001), C. vulgaris IAM C-536, C. sorokiniana IAM C-212, and Trebouxia erici IAM C-593 (Yamamoto et al 2003).…”

Regeneration and maturation of daughter cell walls in the autospore-forming green alga Chlorella vulgaris (Chlorophyta, Trebouxiophyceae)

“…The presence of actin in the cleavage furrow of Chlamydomonas, a member of the Chlorophyceae, suggests that actin provides the generative force for cytokinesis in a manner similar to the contractile-ring microfilaments (Harper et al 1992). In Nannochloris bacillaris Naumann, which belongs to the Trebouxiophyceae along with Chlorella (Yamamoto et al 2001(Yamamoto et al , 2003, Arai et al (1998) showed that actin filaments localize near the nucleus and appear as a belt-like structure in the septum-forming area in the middle of the cell, during cell division. Protoplast division in Chlorella vulgaris seems to involve an actin-based phenomenon, as in other unicellular algae.…”

DNA Content of Stichococcus bacillaris (Trebouxiophyceae, Chlorophyta) Nuclei Determined with Laser Scanning Cytometry

“…Pulse field gel electrophoresis (Higashiyama and Yamada 1991, Arai et al 1998, Yamamoto et al 2001) and flow cytometry (Wilhelm et al 1982, Veldhuis et al 1997 have also been utilized (summarized by Kapraun 2007). The genus Nannochloris and related genera include some of the smallest and ultrastructurally simple phototrophic eukaryotes, with genomes as small as 12.6 Mbp (Arai et al 1998, Yamamoto et al 2001.…”

“…The genus Nannochloris and related genera include some of the smallest and ultrastructurally simple phototrophic eukaryotes, with genomes as small as 12.6 Mbp (Arai et al 1998, Yamamoto et al 2001. The genome size of the binary fission type N. bacillaris was estimated as 20.3 Mbp (Arai et al 1998, Yamamoto et al 2001. LSC functions as both a microscope and a flow cytometer, and is thus able to automatically calculate the total level of fluorescence intensity and simultaneously observe the sample shape.…”