Biomedical subjects

Shoji Mano

Publications and source records attributed to Shoji Mano.

9 recordsLinked to original sources

PubMed2024

Alternative localization of HEME OXYGENASE 1 in plant cells regulates cytosolic heme catabolism.

Heme, an organometallic tetrapyrrole, is widely engaged in oxygen transport, electron delivery, enzymatic reactions, and signal transduction. In plants, it is also involved in photomorphogenesis and photosynthesis. HEME OXYGENASE 1 (HO1) initiates the first committed step in heme catabolism, and it has generally been thought that this reaction takes place in chloroplasts. Here, we show that HO1 in both Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) has 2 transcription start sites (TSSs), producing long (HO1L) and short (HO1S) transcripts. Their products localize to the chloroplast and the cytosol, respectively. During early development or de-etiolation, the HO1L/HO1S ratio gradually increases. Light perception via phytochromes (Phys) and cryptochromes elevates the HO1L/HO1S ratio in the whole seedling through the functions of ELONGATED HYPOCOTYL 5 (HY5) and HY5 HOMOLOG and through the suppression of DE-ETIOLATED 1, CONSTITUTIVE PHOTOMORPHOGENESIS 1, and PHYTOCHROME INTERACTING FACTORs. HO1L introduction complements the HO1-deficient mutant; surprisingly, HO1S expression also restores the short hypocotyl phenotype and high pigment content and helps the mutant recover from the genomes uncoupled (gun) phenotype. This indicates the assembly of functional Phys within these lines. Furthermore, our findings support the hypothesis that a mobile heme signal is involved in retrograde signaling from the chloroplast. Altogether, our work clarifies the molecular mechanism of HO1 TSS regulation and highlights the presence of a cytosolic bypass for heme catabolism in plant cells.

Heme↗

PubMed2006

The Arabidopsis pex12 and pex13 mutants are defective in both PTS1- and PTS2-dependent protein transport to peroxisomes.

Peroxisome biogenesis requires various complex processes including organelle division, enlargement and protein transport. We have been studying a number of Arabidopsis apm mutants that display aberrant peroxisome morphology. Two of these mutants, apm2 and apm4, showed green fluorescent protein fluorescence in the cytosol as well as in peroxisomes, indicating a decrease of efficiency of peroxisome targeting signal 1 (PTS1)-dependent protein transport to peroxisomes. Interestingly, both mutants were defective in PTS2-dependent protein transport. Plant growth was more inhibited in apm4 than apm2 mutants, apparently because protein transport was more severely decreased in apm4 than in apm2 mutants. APM2 and APM4 were found to encode proteins homologous to the peroxins PEX13 and PEX12, respectively, which are thought to be involved in transporting matrix proteins into peroxisomes in yeasts and mammals. We show that APM2/PEX13 and APM4/PEX12 are localized on peroxisomal membranes, and that APM2/PEX13 interacts with PEX7, a cytosolic PTS2 receptor. Additionally, a PTS1 receptor, PEX5, was found to stall on peroxisomal membranes in both mutants, suggesting that PEX12 and PEX13 are components that are involved in protein transport on peroxisomal membranes in higher plants. Proteins homologous to PEX12 and PEX13 have previously been found in Arabidopsis but it is not known whether they are involved in protein transport to peroxisomes. Our findings reveal that APM2/PEX13 and APM4/PEX12 are responsible for matrix protein import to peroxisomes in planta.

Amino Acid Sequence↗

PubMed2005

Peroxisomal localization of a myosin XI isoform in Arabidopsis thaliana.

The genome of Arabidopsis thaliana contains 13 myosin XI isoforms. Here we prepared a specific antibody against a peptide that mimics a unique C-terminal region from the myosin XI isoform, MYA2. The resulting antibody was used to demonstrate that MYA2 in Arabidopsis protein extracts co-sedimented with actin filaments and dissociated from the filaments with ATP treatment. Immunolocalization studies showed that MYA2 co-localized predominantly with actin filaments in clustered punctuate dots in leaf epidermal cells, root hair cells and suspension-cultured cells. In a transgenic plant in which peroxisomes are labeled with green fluorescent protein, some MYA2 signals were localized on peroxisomes in an actin-dependent manner. We propose that the peroxisome is one of the cargos translocated by MYA2 on actin filaments.

Actin Cytoskeleton↗

PubMed2005

Two cis-acting regulatory elements are involved in the sucrose-inducible expression of the sporamin gene promoter from sweet potato in transgenic tobacco.

In this study, we generated transgenic tobacco plants that express the beta-glucuronidase (GUS) gene under the control of the 305-bp 5'-upstream region of a gene coding for sporamin A of sweet potato. Expression of GUS in excised tobacco leaves was induced by sucrose, mimicking the sugar-inducible expression of the endogenous sporamin genes in sweet potato. Deletion of the sequences extending from position -305 (relative to the transcription start site) to -283 and from -146 to -87 resulted in an approximately 40-fold enhancement in GUS reporter expression. Furthermore, the sequence from -282 to -165 conferred sucrose-inducibility on the -89 core promoter of the Cauliflower Mosaic Virus 35S RNA gene. Analysis of internal deletions, linker scanning and the introduction of base substitutions in the sequence between positions -282 and -165 indicated that sucrose-responsiveness conferred by this region was dependent on the presence of two cis-acting elements, termed CMSREs (carbohydrate metabolite signal responsive elements) 1 and 2, which are separated by a spacer. A sequence similar or identical to the core of CMSRE-1 (TGGACGG) is also present in the promoters of several other sugar-inducible genes, and sequences encopassing the TGGACGG-related motifs from two of these could functionally replace the CMSRE-1 in the truncated sporamin A promoter. These results suggest that the TGGACGG element plays an important role in the sucrose-inducible expression of a group of plant genes.

Base Sequence↗

PubMed2005

Plant peroxisomes.

Peroxisomes, one of single membrane-bound organelles, are present ubiquitously in eukaryotic cells. They were originally identified as organelles for production of hydrogen peroxide, the degradation of its hydrogen peroxide, and metabolism of fatty acids, which are functions common to almost all the organisms. Meanwhile, photorespiration and assimilation of symbiotically induced nitrogen are plant-specific functions. Recent postgenetic approaches such as transcriptome and proteome showed that plant peroxisomes are differentiated in various tissues, and revealed that peroxisomes have more important roles in various metabolic processes including biosynthesis of plant hormones than we speculated. All peroxisomal proteins, including metabolic enzymes in the matrix, membrane proteins, and factors responsible for peroxisome biogenesis, are nuclear encoded, and are provided from the outside of peroxisomes. Peroxisome biogenesis, such as protein transport, division, and enlargement, requires various complicated steps and is one of the most intriguing topics. Analyses using peroxisome biogenesis mutants and the whole-scale sequencing projects among several organisms revealed the existence of essential factors responsible for peroxisome biogenesis such as peroxins. This review addresses a comprehensive issue relating to function and biogenesis of plant peroxisomes and Arabidopsis mutants that have been accelerating our understanding of peroxisomes in planta.

Peroxisomes↗

PubMed2004

An Arabidopsis dynamin-related protein, DRP3A, controls both peroxisomal and mitochondrial division.

Peroxisomes undergo dramatic changes in size, shape, number, and position within the cell, but the division process of peroxisomes has not been characterized. We screened a number of Arabidopsis mutants with aberrant peroxisome morphology (apm mutants). In one of these mutants, apm1, the peroxisomes are long and reduced in number, apparently as a result of inhibition of division. We showed that APM1 encodes dynamin-related protein 3A (DRP3A), and that mutations in APM1/DRP3A also caused aberrant morphology of mitochondria. The transient expression analysis showed that DRP3A is associated with the cytosolic side of peroxisomes. These findings indicate that the same dynamin molecule is involved in peroxisomal and mitochondrial division in higher plants. We also report that the growth of Arabidopsis, which requires the cooperation of various organelles, including peroxisomes and mitochondria, is repressed in apm1, indicating that the changes of morphology of peroxisomes and mitochondria reduce the efficiency of metabolism in these organelles.

Amino Acid Sequence↗

PubMed2003

Identification of peroxisomal targeting signal of pumpkin catalase and the binding analysis with PTS1 receptor.

Many peroxisomal proteins are imported into peroxisomes via recognition of the peroxisomal targeting signal (PTS1) present at the C-termini by the PTS1 receptor (Pex5p). Catalase, a peroxisomal protein, has PTS1-like motifs around or at the C-terminus. However, it remains unclear whether catalase is imported into peroxisome via the PTS1 system. In this work, we analyzed the PTS of pumpkin catalase (Cat1). A full or truncated pumpkin Cat1 cDNA fused at the 3' end of the green fluorescent protein (GFP) coding sequence was introduced and stably expressed in tobacco BY-2 (Nicotiana tabacum cv. Bright Yellow 2) cells or Arabidopsis thaliana by Agrobacterium-mediated transformation. The cellular localization of GFP was analyzed by fluorescence microscopy. The results showed that the C-terminal 10-amino acid region containing an SKL motif-like tripeptide (SHL) was not required for the import into peroxisomes. Surprisingly, the C-terminal 3-amino acid region was required for the import when the fusion proteins were transiently expressed by using particle gun bombardment, suggesting that the transient expression system is inadequate to analyze the targeting signal. We proposed that the C-terminal amino acid region from 13 to 11 (QKL), which corresponds with the PTS1 consensus sequence, may function as an internal PTS1. Analysis of the binding of Cat1 to PTS1 receptor (Pex5p) by the yeast two-hybrid system revealed that Cat1 can bind with the PTS1 receptor (Pex5p), indicating that Cat1 is imported into peroxisomes by the PTS1 system.

Base Sequence↗

PubMed2003

Functional differentiation of peroxisomes revealed by expression profiles of peroxisomal genes in Arabidopsis thaliana.

It is well known that peroxisomal matrix proteins contain one of two targeting signals, PTS1 and PTS2. We comprehensively surveyed genes related to peroxisomal function and biogenesis in the entire Arabidopsis genome sequence. Here, we identified 256 gene candidates of PTS1- and PTS2-containing proteins and another 30 genes of non-PTS-containing proteins. Of these, only 29 proteins have been reported to be functionally characterized as peroxisomal proteins in higher plants. We extensively investigated expression profiles of genes described above in various organs of Arabidopsis: Statistical analyses of these expression profiles revealed that peroxisomal genes could be divided into five groups. One group showed ubiquitous expression in all organs examined, while the other four were classified as showing organ-specific expression in seedlings, cotyledons, roots and in both cotyledons and leaves. These data proposed more detailed description of differentiation of plant peroxisomes.

Arabidopsis↗

PubMed2002

Distribution and characterization of peroxisomes in Arabidopsis by visualization with GFP: dynamic morphology and actin-dependent movement.

Peroxisomes were visualized in living cells of various tissues in transgenic Arabidopsis by green fluorescent protein (GFP) through the addition of the peroxisomal targeting signal 1 (PTS1) or PTS2. The observation using confocal laser scanning microscopy revealed that the GFP fluorescence signals were detected as spherical spots in all cells of two kinds of transgenic plants. Immunoelectron microscopic analysis using antibodies against the peroxisomal marker protein, catalase, showed the presence of GFP in peroxisomes, confirming that GFP was correctly transported into peroxisomes by PTS1 or PTS2 pathways. It has been also revealed that peroxisomes are motile organelles whose movement might be caused by cytoplasmic flow. The movement of peroxisomes was more prominent in root cells than that in leaves, and divided into two categories: a relatively slow, random, vibrational movement and a rapid movement. Treatment with anti-actin and anti-tubulin drugs revealed that actin filaments involve in the rapid movement of peroxisomes. Moreover, abnormal large peroxisomes are present as clusters at the onset of germination, and these clusters disappear in a few days. Interestingly, tubular peroxisomes were also observed in the hypocotyl. These findings indicate that the shape, size, number and movement of peroxisomes in living cells are dynamic and changeable rather than uniform.

Actin Cytoskeleton↗