Experimental Investigation of the Mechanism of Reproductive Differentiation in the Queenless Ant,Diacamma sp., from Japan

We test two hypotheses about regulation of the reproductive division of labour in the permanently queenless ponerine ant, Diacamma sp., from Japan. All workers emerge with gemmae (tiny innervated thoracic appendages), but only one individual keeps them in each colony, and she is the only mated reproductive worker (gamergate). The gemmae of all other workers are mutilated by the gamergate soon after their emergence, and they can never mate. In the presence of gamergate, mutilated workers have inactive ovaries and do not behave aggressively. Two possible consequences of mutilation are: 1. olfactory signal — a pheromone inhibiting the oogenesis of mutilated workers is no longer released by the gemmae; and 2. endocrine degeneration of its afferent neuronal connections interferes reproductive physiology of a gamergate. Gemmae of gamergates were coated with shellac (to prevent pheromone emission) or removed, and over three weeks we studied any changes in ovarian activity of the gamergates as well as nestmate workers. Coating of gemmae did not elicit worker oviposition, suggesting that gemmae pheromones do not have a regulatory function. Experimental mutilation of gamergates resulted in a slight increase in both the frequency of dominance interactions and the ovarian activity of mutilated workers, but this effect was much lower than in colonies where the gamergate was removed. This contrasts with the immediate change in the behaviour (aggressive to timid) of newly emerged workers following mutilation.     

Homologous Recombination, but Not DNA Repair, Is Reduced in Vertebrate Cells Deficient in RAD52

Rad52 plays a pivotal role in double-strand break (DSB) repair and genetic recombination in Saccharomyces cerevisiae, where mutation of this gene leads to extreme X-ray sensitivity and defective recombination. Yeast Rad51 and Rad52 interact, as do their human homologues, which stimulates Rad51-mediated DNA strand exchange in vitro, suggesting that Rad51 and Rad52 act cooperatively. To define the role of Rad52 in vertebrates, we generated RAD52^−/− mutants of the chicken B-cell line DT40. Surprisingly, RAD52^−/− cells were not hypersensitive to DNA damages induced by γ-irradiation, methyl methanesulfonate, or cis-platinum(II)diammine dichloride (cisplatin). Intrachromosomal recombination, measured by immunoglobulin gene conversion, and radiation-induced Rad51 nuclear focus formation, which is a putative intermediate step during recombinational repair, occurred as frequently in RAD52^−/− cells as in wild-type cells. Targeted integration frequencies, however, were consistently reduced in RAD52^−/− cells, showing a clear role for Rad52 in genetic recombination. These findings reveal striking differences between S. cerevisiae and vertebrates in the functions of RAD51 and RAD52.     

Cone cells fail to develop normally in transgenic mice showing ablation of rod photoreceptor cells

Transgenic mice were derived containing the cytotoxic dt-α gene driven by opsin promoter sequences. Mice expressing this construct showed progressive degeneration of rod photoreceptor cells commencing at birth, with obvious depletion of such cells by postnatal day 7. Ablation of rod photoreceptor cells in the transgenic retina was accompanied by the failure of developing cone cells to elaborate outer segments, although all other aspects of cone cell cytodifferentiation appeared normal. The results suggest that the 1.0-kb opsin promoter segment contains rod cell type specificity and that cone cells require maturation of rod cells to complete the late stages of their terminal differentiation and for their maintenance and cellular integrity.     

A New Approach to Determine the Effect of Mismatches on Kinetic Parameters in DNA Hybridization Using an Optical Biosensor

We have demonstrated a simple yet direct method for determiningthe kinetic parameters in DNA-DNA interactions using biosensortechnology based on the surface plasmon resonance phenomenon;a technique that does not require complex DNA labeling. To determinethe effect of mismatches on the kinetics involved in DNA-DNAinteractions, DNA hybridization kinetics were monitored in realtime using synthetic oligonucleotides less than 20 bases inlength which contained either a complementary sequence or mismatchedbases. Upon analysis of the kinetic parameters obtained in oligonucleotidehybridization, we found that they were significantly affectedby the presence of mismatches as well as by their number andlocation in a DNA duplex. In addition, the presented biosensormethod is sensitive enough to detect kinetic effects causedby the presence of a single-mismatched base pair. Our findingsstrongly suggest that analysis of kinetic parameters involvedin DNA-DNA interactions is advantageous for detecting the presenceof mismatch base pairs in a DNA duplex.     

Emergence of Antagonism Against the Pathogenic Fungus Fusarium oxysporum by Interplay Among Non‐Antagonistic Bacteria in a Hydroponics Using Multiple Parallel Mineralization

The rhizosphere microbial community in a multiple parallel mineralization (MPM) system contributes to suppression of root‐borne diseases. We hypothesized this phenomenon can be attributed to the interplay of non‐antagonistic bacteria rather than to a single antagonistic microbe. In this study, we tested this hypothesis by investigating the potential roles of bacterial interplay in a subset of MPM microbiota in the suppression of the fungal phytopathogen Fusarium oxysporum. Bacterial strains isolated from the MPM system were subjected to in vitro and in planta tests on F. oxysporum. A community of seven bacterial strains (Kaistia sp. TBD58, Sphingopyxis sp. TBD84, Bosea sp. TBD101, Ancylobacter sp. TBD132, Cupriavidus sp. TBD162, Brevibacillus sp. TBD179 and Sphingopyxis sp. TBD181) suppressed F. oxysporum growth. None of the strains alone was antagonistic against F. oxysporum, whereas several pairs of those non‐antagonistic strains inhibited its growth. Morphological observations showed the formation of swollen F. oxysporum cells in the presence of these bacterial pairs. The same bacterial pairs also suppressed Fusarium wilt disease in Arabidopsis thaliana. These results indicate that a complex bacterial interplay among non‐antagonistic bacteria can significantly contribute to the development of antagonism against F. oxysporum in the context of the MPM system.     

Enhancement of natural killer activity and IFN-γ production in an IL-12-dependent manner by a Brassica rapa L.

Abstract

Certain food components possess immunomodulatory effects. The aim of this study was to elucidate the mechanism of the immunostimulatory activity of Brassica rapa L. We demonstrated an enhancement of natural killer (NK) activity and interferon (IFN)-γ production in mice that were orally administered an insoluble fraction of B. rapa L. The insoluble fraction of B. rapa L. significantly induced IFN-γ production in mouse spleen cells in an interleukin (IL)-12-dependent manner, and NK1.1⁺ cells were the main cells responsible for producing IFN-γ. Additionally, the results suggested that the active compounds in the insoluble fraction were recognized by Toll-like receptor (TLR) 2, TLR4, and C-type lectin receptors on dendritic cells, and they activated signaling cascades such as MAPK, NF-κB, and Syk. These findings suggest that B. rapa L. is a potentially promising immuno-improving material, and it might be useful for preventing immunological disorders such as infections and cancers by activating innate immunity.