Biology subjects

Hayashi, C.

Publications and source records attributed to Hayashi, C..

4 recordsLinked to original sources

bioRxiv2025

Dynamic DnaA-DnaB interactions at oriC coordinate the loading and coupled translocation of two DnaB helicases for bidirectional replication

Bidirectional replication is a conserved principle requiring the coordinated loading and activation of two replicative helicases at the origin. In Escherichia coli, the initiator protein DnaA constructs a higher-order initiation complex at the origin oriC which locally unwinds the DNA, and recruits DnaB helicase-DnaC loader complexes to the unwound region. We previously demonstrated that the two DnaA subcomplexes formed on oriC bind a specific DNA strand of the unwound origin, and tether individual DnaB-DnaC complexes via stable interactions between DnaA domain I and DnaB. A low-affinity DnaA-DnaB interaction mediated by DnaA domain III His136 is essential for DnaB-dependent origin unwinding. Here, we identified DnaB Thr86 as the critical residue mediating this low-affinity interaction. Structural modelling suggests that Thr86 is surface-exposed near the DNA entry site of DnaB. Functional analyses revealed that DnaB Thr86 was specifically required for DnaB loading onto the DnaA-bound strand of the unwound oriC. Furthermore, this strand-specific DnaB loading was required for enabling translocation of the opposing DnaB helicase loaded on the DnaA-free strand. Our findings define a novel regulatory mechanism of strand-specific helicase loading, mediated by the low-affinity DnaA-DnaB interactions, which ensures the coordinated loading and translocation of DnaB helicases for bidirectional replication from oriC.

molecular biology↗

bioRxiv2022

Controlling stomatal aperture, a potential strategy for managing plant bacterial disease

Bacterial blight of crucifers caused by Pseudomonas cannabina pv. alisalensis (Pcal) inflicts great damage on crucifer production. To explore efficient and sustainable strategies for Pcal disease control, we here investigated and screened for amino acids with reduced disease development. We found that exogenous foliar application with multiple amino acids reduced disease symptoms and bacterial populations in cabbage after spray-inoculation, but not syringe-inoculation. These results indicate that these amino acids showed a protective effect before Pcal entered plants. Therefore, we observed stomatal responses, which is a main gateway for Pcal entry into the apoplast, after amino acid treatments, and found several amino acids induce stomatal closure. Moreover, our findings demonstrated that reducing stomatal aperture width can limit bacterial entry into plants, leading to reduced disease symptoms. Therefore, managing stomatal aperture can be a new powerful strategy for controlling bacterial disease.

plant biology↗

bioRxiv2020

Transposable element control disrupted by meiotic drive in a stalk-eyed fly genome

Some stalk-eyed flies in the genus Teleopsis carry selfish genetic elements that induce sex ratio meiotic drive (SR) and impact the fitness of male and female carriers. Here, we produced a chromosome-level genome assembly of the stalk-eyed fly, T. dalmanni, to elucidate patterns of genomic divergence associated with the presence of drive elements. We find evidence for multiple nested inversions along the sex ratio haplotype and widespread differentiation and divergence between XSR and XSR along the entire chromosome. These include a striking XSR-specific expansion of an array of partial copies of JASPer, a gene necessary for maintenance of euchromatin and regulation of transposable element expression (TEs). In addition, the genome contains tens of thousands of TE insertions and hundreds of transcriptionally and insertionally active TE families. Moreover, we find that several TE families are differentially expressed and/or present at a different copy number in SR male testes, suggesting an association between these two categories of selfish genetic elements in this species. We identify T. dalmanni orthologs of genes involved in genome defense via the piRNA pathway, including core members maelstrom, piwi and Argonaute3, that have diverged in sequence, expression or copy number between the SR and standard (ST) X chromosomes, consistent with altered TE regulation in flies carrying a sex ratio X chromosome. Overall, the evidence suggests that this ancient XSR polymorphism has had a variety of impacts on repetitive DNA and its regulation in this species.

evolutionary biology↗

bioRxiv2017

The house spider genome reveals an ancient whole-genome duplication during arachnid evolution

The duplication of genes can occur through various mechanisms and is thought to make a major contribution to the evolutionary diversification of organisms. There is increasing evidence for a large-scale duplication of genes in some chelicerate lineages including two rounds of whole genome duplication (WGD) in horseshoe crabs. To investigate this further we sequenced and analyzed the genome of the common house spider Parasteatoda tepidariorum. We found pervasive duplication of both coding and non-coding genes in this spider, including two clusters of Hox genes. Analysis of synteny conservation across the P. tepidariorum genome suggests that there has been an ancient WGD in spiders. Comparison with the genomes of other chelicerates, including that of the newly sequenced bark scorpion Centruroides sculpturatus, suggests that this event occurred in the common ancestor of spiders and scorpions and is probably independent of the WGDs in horseshoe crabs. Furthermore, characterization of the sequence and expression of the Hox paralogs in P. tepidariorum suggests that many have been subject to neofunctionalization and/or subfunctionalization since their duplication, and therefore may have contributed to the diversification of spiders and other pulmonate arachnids.

genomics↗