Publications by authors named "Toshihiko Eki"

Cyanobacteriochromes (CBCRs) are members of the phytochrome superfamily of photosensor proteins that bind a bilin chromophore. CBCRs exhibit substantial diversity in their absorption wavelengths through a variety of bilin-protein interactions. RcaE is the first discovered cyanobacteriochrome as a regulator of chromatic acclimation, where cyanobacteria optimize the absorption wavelength of their photosynthetic antenna.

View Article and Find Full Text PDF
Article Synopsis
  • Certain cyanobacteria can switch their light absorption between green and red, a process known as complementary chromatic acclimation.
  • This mechanism is controlled by a photosensor that toggles between two states, green-absorbing (Pg) and red-absorbing (Pr), based on light exposure.
  • The research explains the structural changes in the bilin chromophore during this switch, revealing how it affects light absorption and contributes to the diversity of the phytochrome superfamily.
View Article and Find Full Text PDF

Microorganism-based genotoxicity assessments are vital for evaluating potential chemical-induced DNA damage. In this study, we developed both chromosomally integrated and single-copy plasmid-based reporter assays in budding yeast using a RNR3 promoter-driven luciferase gene. These assays were designed to compare the response to genotoxic chemicals with a pre-established multicopy plasmid-based assay.

View Article and Find Full Text PDF

Mutagens and oxidative agents damage biomolecules, such as DNA; therefore, detecting genotoxic and oxidative chemicals is crucial for maintaining human health. To address this, we have developed several types of yeast-based reporter assays designed to detect DNA damage and oxidative stress. This study aimed to develop a novel yeast-based assay using a codon-optimized stable or unstable NanoLuc luciferase (yNluc and yNluCP) gene linked to a DNA damage- or oxidative stress-responsive promoter, enabling convenient sensing genotoxicity or oxidative stress, respectively.

View Article and Find Full Text PDF

Crop rotation is an important agricultural practice for homeostatic crop cultivation. Here, we applied high-throughput sequencing of ribosomal RNA gene amplicons to investigate soil biota in two fields of central Japan with different histories of maize-cabbage rotation. We identified 3086 eukaryotic and 17,069 prokaryotic sequence variants (SVs) from soil samples from two fields rotating two crops at three different growth stages.

View Article and Find Full Text PDF

Cyanobacteria are phototrophic bacteria that perform oxygenic photosynthesis. They use a supermolecular light-harvesting antenna complex, the phycobilisome (PBS), to capture and transfer light energy to photosynthetic reaction centers. Certain cyanobacteria alter the absorption maxima and/or overall structure of their PBSs in response to the ambient light wavelength-a process called chromatic acclimation (CA).

View Article and Find Full Text PDF

Cyanobacteriochromes (CBCRs) belong to the phytochrome superfamily of photoreceptors, the members of which utilize a linear tetrapyrrole (bilin) as a chromophore. RcaE is a representative member of a green/red-type CBCR subfamily that photoconverts between a green-absorbing dark state and red-absorbing photoproduct (Pr). Our recent crystallographic study showed that the phycocyanobilin (PCB) chromophore of RcaE adopts a unique C15-, configuration in the Pr state, unlike the typical C15-, configuration for the phytochromes and other CBCRs.

View Article and Find Full Text PDF

Nematodes are abundant metazoans that play crucial roles in nutrient recycle in the pedosphere. Although high-throughput amplicon sequencing is a powerful tool for the taxonomic profiling of soil nematodes, polymerase chain reaction (PCR) primers for amplification of the 18S ribosomal RNA (SSU) gene and preparation of template DNAs have not been sufficiently evaluated. We investigated nematode community structure in copse soil using four nematode-specific (regions 1-4) and two universal (regions U1 and U2) primer sets for the SSU gene regions with two DNAs prepared from copse-derived mixed nematodes and whole soil.

View Article and Find Full Text PDF

Cyanobacteria are a diverse group of Gram-negative prokaryotes that perform oxygenic photosynthesis. Cyanobacteria have been used for research on photosynthesis and have attracted attention as a platform for biomaterial/biofuel production. Cyanobacteria are also present in almost all habitats on Earth and have extensive impacts on global ecosystems.

View Article and Find Full Text PDF

Cyanobacteriochromes (CBCRs) are bilin-binding photosensors of the phytochrome superfamily that show remarkable spectral diversity. The green/red CBCR subfamily is important for regulating chromatic acclimation of photosynthetic antenna in cyanobacteria and is applied for optogenetic control of gene expression in synthetic biology. It is suggested that the absorption change of this subfamily is caused by the bilin C15/C15- photoisomerization and a subsequent change in the bilin protonation state.

View Article and Find Full Text PDF

Quantitative taxonomic compositions of nematode communities help to assess soil environments due to their rich abundance and various feeding habitats. DNA metabarcoding by the 18S ribosomal RNA gene (SSU) regions were preferentially used for analyses of soil nematode communities, but the optimal regions for high-throughput amplicon sequencing have not previously been well investigated. In this work, we performed Illumina-based amplicon sequencing of four SSU regions (regions 1-4) to identify suitable regions for nematode metabarcoding using the taxonomic structures of nematodes from uncultivated field, copse, and cultivated house garden soils.

View Article and Find Full Text PDF

Linear tetrapyrrole compounds (bilins) are chromophores of the phytochrome and cyanobacteriochrome classes of photosensors and light-harvesting phycobiliproteins. Various spectroscopic techniques, such as resonance Raman, Fourier transform-infrared and nuclear magnetic resonance, have been used to elucidate the structures underlying their remarkable spectral diversity, in which the signals are experimentally assigned to specific structures using isotopically labeled bilin. However, current methods for isotopic labeling of bilins require specialized expertise, time-consuming procedures and/or expensive reagents.

View Article and Find Full Text PDF

Nematodes are representative soil metazoans with diverged species that play crucial roles in nutrient recycling in the pedosphere. Qualitative and quantitative information on nematode communities is useful for assessing soil quality, and DNA barcode-mediated taxonomic analysis is a powerful tool to investigate taxonomic compositions and changes in nematode communities. Here, we investigated four regions (regions 1-4) of the 18S small subunit ribosomal RNA (SSU) gene as PCR targets of deep amplicon sequencing for the taxonomic profiling of individual soil nematodes.

View Article and Find Full Text PDF

Amplicon sequencing is a powerful approach in microbiome studies as it detects live organisms with high sensitivity. This approach determines the composition of sequence variants of marker genes using high-throughput DNA sequencers. The use of dual index adaptors is the fundamental technique for pooling DNA libraries for Illumina sequencers and is believed not to affect the results.

View Article and Find Full Text PDF

The Dicer-related helicases (DRHs) are members of a helicase subfamily, and mammalian DRHs such as retinoic acid-inducible gene-I (RIG-I), are involved in antiviral immunity. DRH-1 and DRH-3 play crucial roles in antiviral function and chromosome segregation, respectively. Although intrinsic double-stranded RNA-dependent ATP-hydrolyzing activity has been observed in the recombinant DRH-3 protein prepared from , there are no reports of biochemical studies of the nematode RIG-I homolog DRH-1.

View Article and Find Full Text PDF

Antarctica has one of the most extreme environments on Earth, with low temperatures and low nutrient levels. Antarctica's organisms live primarily in the coastal, ice-free areas which cover approximately 0.18% of the continent's surface.

View Article and Find Full Text PDF

The biodiversity of phototrophic purple nonsulfur bacteria (PNSB) in comparison with purple sulfur bacteria (PSB) in colored blooms and microbial mats that developed in coastal mudflats and pools and wastewater ditches was investigated. For this, a combination of photopigment and quinone profiling, gene-targeted quantitative PCR, and gene clone library analysis was used in addition to conventional microscopic and cultivation methods. Red and pink blooms in the coastal environments contained PSB as the major populations, and smaller but significant densities of PNSB, with members of predominating.

View Article and Find Full Text PDF

Cyanobacteriochromes (CBCRs) are phytochrome-related photosensors with diverse spectral sensitivities spanning the entire visible spectrum. They covalently bind bilin chromophores via conserved cysteine residues and undergo bilin photoisomerization upon light illumination. CBCR subfamilies absorbing violet-blue light use an additional cysteine residue to form a second bilin-thiol adduct in a two-Cys photocycle.

View Article and Find Full Text PDF

Cyanobacteria have evolved various photoacclimation processes to perform oxygenic photosynthesis under different light environments. Chromatic acclimation (CA) is a widely recognized and ecologically important type of photoacclimation, whereby cyanobacteria alter the absorbing light colors of a supermolecular antenna complex called the phycobilisome. To date, several CA variants that regulate the green-absorbing phycoerythrin (PE) and/or the red-absorbing phycocyanin (PC) within the hemi-discoidal form of phycobilisome have been characterized.

View Article and Find Full Text PDF

By damaging DNA molecules, genotoxicants cause genetic mutations and also increase human susceptibility to cancers and genetic diseases. Over the past four decades, several assays have been developed in the budding yeast Saccharomyces cerevisiae to screen potential genotoxic substances and provide alternatives to animal-based genotoxicity tests. These yeast-based genotoxicity tests are either DNA alteration-based or DNA stress-response reporter-based.

View Article and Find Full Text PDF

Certain cyanobacteria can adjust the wavelengths of light they absorb by remodeling their photosynthetic antenna complex phycobilisome via a process called chromatic acclimation (CA). Although several types of CA have been reported, the diversity of the molecular mechanisms of CA among the cyanobacteria phylum is not fully understood. Here, we characterized the molecular process of CA of Geminocystis sp.

View Article and Find Full Text PDF

We aimed to develop the bioassays for genotixicity and/or oxidative damage using the recombinant yeast. A genotoxicity assay was developed using recombinant Saccharomyces cerevisiae strain BY4741 with a green fluorescent protein (GFP) reporter plasmid, driven by the DNA damage-responsive RNR3 promoter. Enhanced fluorescence induction was observed in DNA repair-deficient strains treated with methyl methanesulfonate, but not with hydrogen peroxide.

View Article and Find Full Text PDF

Cyanobacterial genus Leptolyngbya comprises genetically diverse species, but the availability of their complete genome information is limited. Here, we isolated Leptolyngbya sp. strain NIES-3755 from soil at the Toyohashi University of Technology, Japan.

View Article and Find Full Text PDF

A PHP Error was encountered

Severity: Warning

Message: fopen(/var/lib/php/sessions/ci_sessionq3runb190qntoqu2ad31kr8ru5tr9sj5): Failed to open stream: No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 177

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once

A PHP Error was encountered

Severity: Warning

Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)

Filename: Session/Session.php

Line Number: 137

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once