Faculty Profiles - SAKAMOTO Wataru

[Maternal inheritance of mitochondria in higher plants].

Sodmergen, Wataru Sakamoto

Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 50 ( 14 Suppl ) 1795 - 8 2005.11

[Dynamics in mitochondria and chloroplasts: a current overview].

Wataru Sakamoto, Jun-Ichi Hayashi

Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 50 ( 14 Suppl ) 1861 - 2 2005.11

[Role of ATP-dependent proteolytic machineries in plastid biogenesis, differentiation, maintenance, and senescence].

Wataru Sakamoto

Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 50 ( 14 Suppl ) 1892 - 5 2005.11

Protein quality control and membrane proteases in chloroplasts

Sakamoto, W

Seikagaku 77 ( 4 ) 2005

FtsH proteases in chloroplasts and cyanobacteria

Adam, Z, Zaltsman, A, Sinvany-Villalobo, G, Sakamoto, W

Physiologia Plantarum 123 ( 4 ) 2005

Isolation and molecular characterization of rbcS in the unicellular green alga Nannochloris bacillaris (Chlorophyta, Trebouxiophyceae)

Yamazaki, T, Yamamoto, M, Sakamoto, W, Kawano, S

Phycological Research 53 ( 1 ) 2005

An Arabidopsis mutant deficient in pollen mitosis II

Kubo, M, Sakamoto, W

Plant and Cell Physiology 46 2005

Quality control of membrane proteins in chloroplasts and its relationship to light adaptation

Sakamoto, W

Plant and Cell Physiology 46 2005

Isolation of mutations that suppress leaf variegation in var2 of Arabidopsis

Miura, E, Sakamoto, W

Plant and Cell Physiology 46 2005

Isolation and characterization of Ty1/copia-like reverse transcriptase sequences from mung bean

Xiao, WM, Sakamoto, W, Sodmergen

Acta Botanica Sinica 46 ( 5 ) 2004

Allelic characterization of the leaf-variegated mutation var2 identifies the conserved amino acid residues of FtsH that are important for ATP hydrolysis and proteolysis International journal

Sakamoto, W, Miura, E, Kaji, Y, Okuno, T, Nishizono, M, Ogura, T

Plant Molecular Biology 56 ( 5 ) 705 - 16 2004

Language：English Publishing type：Research paper (scientific journal)

Arabidopsis var1 and var2 mutants exhibit leaf variegation. VAR1 and VAR2 encode similar FtsH metalloproteases (FtsH5 and FtsH2, respectively). We have previously found many variegated mutants to be allelic to var2. Each mutant was shown to express a different degree of variegation, and the formation of white sectors was enhanced in severely variegated alleles when these alleles were grown at low temperature. VAR1/FtsH5 and VAR2/FtsH2 levels were mutually affected even in the weak alleles, confirming our previous observation that the two proteins form a hetero complex. In this study, the sites of the mutations in these var2 alleles were determined. We isolated eight point mutations. Five alleles resulted in an amino acid substitution. Three of the five amino acid substitutions occurred in Walker A and B motifs of the ATP-binding site, and one occurred in the central pore motif. These mutations were considered to profoundly suppress the ATPase and protease activities. In contrast, one mutation was found in a region that contained no obvious signature motifs, but a neighboring sequence, Gly-Ala-Asp, was highly conserved among the members of the AAA protein family. Site-directed mutagenesis of the corresponding residue in E. coli FtsH indeed showed that this residue is necessary for proper ATP hydrolysis and proteolysis. Based on these results, we propose that the conserved Gly-Ala-Asp motif plays an important role in FtsH activity. Thus, characterization of the var2 alleles could help to identify the physiologically important domain of FtsH.

DOI： 10.1007/s11103-004-4561-9

A mutation of the CRUMPLED LEAF gene that encodes a protein localized in the outer envelope membrane of plastids affects the pattern of cell division, cell differentiation, and plastid division in Arabidopsis International journal

Asano, T, Yoshioka, Y, Kurei, S, Sakamoto, W, Machida, Y

Plant Journal 38 ( 3 ) 448 - 59 2004

Language：English Publishing type：Research paper (scientific journal)

We identified a novel mutation of a nuclear-encoded gene, designated as CRUMPLED LEAF (CRL), of Arabidopsis thaliana that affects the morphogenesis of all plant organs and division of plastids. Histological analysis revealed that planes of cell division were distorted in shoot apical meristems (SAMs), root tips, and embryos in plants that possess the crl mutation. Furthermore, we observed that differentiation patterns of cortex and endodermis cells in inflorescence stems and root endodermis cells were disturbed in the crl mutant. These results suggest that morphological abnormalities observed in the crl mutant were because of aberrant cell division and differentiation. In addition, cells of the crl mutant contained a reduced number of enlarged plastids, indicating that the division of plastids was inhibited in the crl. The CRL gene encodes a novel protein with a molecular mass of 30 kDa that is localized in the plastid envelope. The CRL protein is conserved in various plant species, including a fern, and in cyanobacteria, but not in other organisms. These data suggest that the CRL protein is required for plastid division, and it also plays an important role in cell differentiation and the regulation of the cell division plane in plants. A possible function of the CRL protein is discussed.

DOI： 10.1111/j.1365-313X.2004.02057.x

Isolation of mutants with aberrant mitochondrial morphology from Arabidopsis thaliana

Feng, XG, Arimura, S, Hirano, HY, Sakamoto, W, Tsutsumi, N

Genes & Genetic Systems 79 ( 5 ) 301 - 5 2004

Language：English Publishing type：Research paper (scientific journal)

To identify genes related to plant mitochondrial morphology and dynamics, novel mutants with respect to mitochondrial morphology were isolated from an ethyl methane sulphonate (EMS)-mutated population of Arabidopsis thaliana. Mitochondria were visualized by transforming Arabidopsis with a gene for a fusion protein consisting of GFP and a mitochondria-targeting pre-sequence. From 19,000 M2 populations, 17 mutants were isolated by fluorescent microscopic observations. All mitochondria in these mutants were longer and/or larger than wild-type mitochondria. The approximate chromosomal loci of the mutations of seven mutants that grew well were determined. The mitochondrial phenotypes of six of the mutants were recessive but the mitochondrial phenotype of the seventh mutant was dominant. Chromosomal rough mapping of the seven mutants showed that the mutations occurred at four different loci. At least one of these loci was novel, i.e., it was different from loci of other known mitochondrial morphology mutants of Arabidopsis and different from loci of Arabidopsis homologues of yeast genes related to mitochondrial morphology.

DOI： 10.1266/ggs.79.301

Analysis of the CRUMPLED LEAF that is involved in the plastid division, cell division, and cell differentiation in Arabidopsis thaliana Reviewed

Molecular divergence and characterization of two chloroplast division genes, Ftsz1 and Ftsz2, in the unicellular green alga Nannochloris bacillaris (Chlorophyta)

Koide, T, Yamazaki, T, Yamamoto, M, Fujishita, M, Nomura, H, Moriyama, Y, Sumiya, N, Matsunaga, S, Sakamoto, W, Kawano, S

Journal of Phycology 40 ( 3 ) 2004

Asano T, Yoshioka Y, Kurei S, Sakamoto W, Dmergen S, Fujiwara M, Yoshida S, Machida Y

Plant and Cell Physiology 45 S21 2004

Leaf-variegated mutations and their responsible genes in Arabidopsis thaliana

Sakamoto, W

Genes & Genetic Systems 78 ( 1 ) 1 - 9 2003

Language：English Publishing type：Research paper (scientific journal)

Leaf variegation has long been known as a recessive genetic trait in higher plants. Unlike albino mutants, leaf-variegated mutants are non-lethal and thus enable us to study a novel mechanism of plastid development and maintenance. Variegation results from a defect that makes chloroplast development unstable, since at least part of the tissues gives rise to normal chloroplasts. Despite the fact that leaf-variegated mutants have contributed to the findings of maternal inheritance or have been used as genetic markers, these mutations and the responsible loci have been poorly understood at the molecular level. A comprehensive study of the leaf-variegated mutants is possible in Arabidopsis, since such mutants have been known and the cloning can be at relative ease as a model plant. Here I summarize recent progress on characterization of the Arabidopsis leaf-variegated mutants. Detailed analysis of the responsible loci revealed that variegation is caused by a defect in various metabolic pathways related to organelle functions. Thus, studies on these genes provide us with novel redundant mechanisms by which heteroplasmic organelles such as plastids and mitochondria can survive from an environmental stress.