WAM to SeeSaw model for cancer therapy - overcoming LQM difficulties.

Purpose: The assessment of biological effects caused by radiation exposure has been currently carried out with the linear-quadratic (LQ) model as an extension of the linear non-threshold (LNT) model. In this study, we suggest a new mathematical model named as SeaSaw (SS) model, which describes proliferation and cell death effects by taking account of Bergonie-Tribondeau's law in terms of a differential equation in time. We show how this model overcomes the long-standing difficulties of the LQ model.

Selective Activation of Chloroplast psbD Light-Responsive Promoter and psaA/B Promoter in Transplastomic Tobacco Plants Overexpressing Arabidopsis Sigma Factor AtSIG5.

Background: Plastid-encoded eubacterial-type RNA polymerase (PEP) plays a critical role in the transcription of photosynthesis genes in chloroplasts. Notably, some of the reaction center genes, including psaA, psaB, psbA, and psbD genes, are differentially transcribed by PEP in mature chloroplasts. However, the molecular mechanism of promoter selection in the reaction center gene transcription by PEP is not well understood.

Study of mutation from DNA to biological evolution.

This is a paper based on a talk given in the BER2018 conference by M. Bando. We first emphasize the importance of collaborations among scientists in various fields for the low dose/dose-rate effects on biological body.

Verification of a dose rate-responsive dynamic equilibrium model on radiation-induced mutation frequencies in mice.

We have proposed a mathematical model (WAM model) expressing increment of the dose-rate dependent mutation frequency caused by artificial radiations. In this model, it is defined that the pool of mutant cells in dynamic equilibrium in organisms. We verified the accuracy of the WAM prediction of mutation frequency in mice.

Structural and functional characterisation of the cyanobacterial PetC3 Rieske protein family.

The cyanobacterium Synechocystis PCC 6803 possesses three Rieske isoforms: PetC1, PetC2 and PetC3. While PetC1 and PetC2 have been identified as alternative subunits of the cytochrome bf complex (bf), PetC3 was localized exclusively within the plasma membrane. The spatial separation of PetC3 from the photosynthetic and respiratory protein complexes raises doubt in its involvement in bioenergetic electron transfer.

Structure of a thermophilic cyanobacterial b6f-type Rieske protein.

The `Rieske protein' PetC is one of the key subunits of the cytochrome b(6)f complex. Its Rieske-type [2Fe-2S] cluster participates in the photosynthetic electron-transport chain. Overexpression and careful structure analysis at 2.

Multiple Rieske proteins enable short- and long-term light adaptation of Synechocystis sp. PCC 6803.

In contrast to eukaryotes, most cyanobacteria contain several isoforms of the Rieske iron-sulfur protein, PetC, resulting in heterogeneity in the composition of the cytochrome b(6)f complexes. Of three isoforms in the mesophilic cyanobacterium Synechocystis PCC 6803, PetC1 is the major Rieske protein in the cytochrome b(6)f complex, whereas the physiological function of PetC2 and PetC3 is still uncertain. Comparison of wild type and various petC-deficient strains under selected light conditions revealed distinct functional differences: high-light exposure of wild type cells resulted in a significantly enhanced petC2 transcript level, whereas a Delta petC1 mutant showed a low cytochrome b(6)f content, low electron flux, and a considerably increased accumulation of cytochrome-bd oxidase.

Two novel nuclear genes, OsSIG5 and OsSIG6, encoding potential plastid sigma factors of RNA polymerase in rice: tissue-specific and light-responsive gene expression.

Two novel nuclear genes, OsSIG5 and OsSIG6, encoding potential plastid sigma factors of RNA polymerase (RNAP) were identified in Oryza sativa. The deduced amino acid sequences contain conserved regions, regions 1.2-4.

Plastid RNA polymerases, promoters, and transcription regulators in higher plants.

Plastids are semiautonomous plant organelles exhibiting their own transcription-translation systems that originated from a cyanobacteria-related endosymbiotic prokaryote. As a consequence of massive gene transfer to nuclei and gene disappearance during evolution, the extant plastid genome is a small circular DNA encoding only ca. 120 genes (less than 5% of cyanobacterial genes).

A nuclear-encoded sigma factor, Arabidopsis SIG6, recognizes sigma-70 type chloroplast promoters and regulates early chloroplast development in cotyledons.

Eubacterial-type multi-subunit plastid RNA polymerase (PEP) is responsible for the principal transcription activity in chloroplasts. PEP is composed of plastid-encoded core subunits and one of multiple nuclear-encoded sigma factors that confer promoter specificity on PEP. Thus, the replacement of sigma factors associated with PEP has been assumed to be a major mechanism for the switching of transcription patterns during chloroplast development.

Blue light-induced transcription of plastid-encoded psbD gene is mediated by a nuclear-encoded transcription initiation factor, AtSig5.

Light is one of the most important environmental factors regulating expression of photosynthesis genes. The plastid psbD gene encoding the photosystem II reaction center protein D2 is under the control of a unique blue light responsive promoter (BLRP) that is transcribed by a bacterial-type plastid RNA polymerase (PEP). Promoter recognition of PEP is mediated by one of the six nuclear-encoded sigma factors in Arabidopsis.

Blue light specific and differential expression of a plastid sigma factor, Sig5 in Arabidopsis thaliana.

The transcription of plastid gene psbD is under the control of the BLRP (blue-light-responsive promoter) recognized by plastid-encoded RNA polymerase, in which nuclear-encoded sigma factors play a crucial role in the promoter recognition. We examined the effects of light on mRNA levels of six different SIG genes in Arabidopsis and found that blue light extensively induced the accumulation of SIG5 transcripts, but red light did not. The blue light specificity was not observed in the accumulations of remaining five SIG genes.