Long-term coexistence of a hybridization-derived population of Drosophila parapallidosa with closely related Drosophila ananassae (Diptera: Drosophilidae)

A 2012–13 survey on Penang Island, Malaysia, revealed the existence of both Drosophila ananassae and Drosophila parapallidosa, the latter of which carries chromosomes Y and 4 from D. ananassae and thus is of hybrid origin. We collected the flies again from the same location in 2018. The hybrid population remained present, which suggests that the D. parapallidosa of hybrid origin does not represent a mere transient population but is stable. Why do these two species coexist irrespective of gene flow? We realized that body size is generally larger in D. ananassae than in D. parapallidosa, which constitutes a new character with which to discriminate these species; previously the number of sex comb teeth was the only diagnostic trait. Character displacement was not detected, however, for those traits. We crossed these two species, which resulted in offspring that had an altered genomic constitution. The body size of D. ananassae was dominant, and the presence of chromosomes Y and 4 did not have a significant effect on body size. By contrast, the presence of chromosome 4 from D. ananassae significantly affected the number of sex comb teeth. Even flies having a genomic constitution similar to that of the Penang D. parapallidosa exhibited a number of sex comb teeth that was intermediate between the two species. We propose that the D. parapallidosa sex comb character underwent selection during evolution of the Penang Island population. Reproductive interference between the species, presumably caused by signal jamming, was detected.     

A megapterygium larva of <Emphasis Type="Italic">Discoverichthys praecox</Emphasis> (Aulopiformes: Ipnopidae) from the tropical western Pacific

The larva of Discoverichthys (Aulopiformes: Ipnopidae) is described for the first time based on a specimen 39.5 mm in standard length collected in surface waters near the Marianas in the western North Pacific. Despite its remote location from the previous record in eastern North Atlantic (type locality), this larva was identified as Discoverichthys praecox by general agreements of meristic counts and other morphological features. It is characterized by the following possible autapomorphic features: body moderately elongate, with uniformly distended abdomen, terminating in long, stout trailing gut; all fins, particularly the pectoral and pelvic, are extensively produced; body pigmentation is scanty, but all fins except the caudal are polka-dotted distally and covered by unusually thick skin; the skeleton is largely cartilaginous, with poorly differentiated axial components and uniquely expanded dorsal- and anal-fin pterygiophores. Its peculiar morphology is discussed with special reference to transformation events.     

Reproductive behaviour of the filefishRudarius ercodes: male spawning parades and female choice

Synopsis The reproductive behaviour ofRudarius ercodes is described from undersea observations in Aburatsubo Bay, Japan. Reproductive behaviour can be separated into four parts: (1) Prespawning Search = searching for spawning sites by females and searching for gravid females by males, (2) Spawning Parade = males follow a gravid female in a line, competing with each other to reach the head of the queue, (3) Spawning = the female takes the spawning position, males rush to the side of the female, and mating occurs between one female and several anterior males of the spawning parade, (4) Parental Care = females attach adhesive eggs to seaweed with the mouth and guard them until embryos hatch. There is no male parental care. The reproductive season ranges from May to October and spawning occurs early in the morning every day. Females begin feeding early in the morning, but males feed little at this time.R. ercodes shows neither territorial behaviour nor fixed-pair spawning. One male might spawn several times in one morning. One female spawns at most once every 5 days. The mating system of this species is promiscuous. The probable function of the spawning parade as a style allowing female choice is discussed.     

Disruption of a novel gene for a NAC-domain protein in rice confers resistance to Rice dwarf virus

Rice dwarf virus (RDV) is a serious viral pest that is transmitted to rice plants ( Oryza sativa L.) by leafhoppers and causes a dwarfism in infected plants. To identify host factors involved in the multiplication of RDV, we screened Tos17 insertion mutant lines of rice for mutants with reduced susceptibility to RDV. One mutant, designated rim1-1 , did not show typical disease symptoms upon infection with RDV. The accumulation of RDV capsid proteins was also drastically reduced in inoculated rim1-1 mutant plants. Co-segregation and complementation analyses revealed that the rim1-1 mutation had been caused by insertion of Tos17 in an intron of a novel NAC gene. The rim1-1 mutant remained susceptible to the two other viruses tested, one of which is also transmitted by leafhoppers, suggesting that the multiplication rather than transmission of RDV is specifically impaired in this mutant. We propose that RIM1 functions as a host factor that is required for multiplication of RDV in rice.     

Prolonged survival in mice with advanced tumors treated with syngeneic or allogeneic intra-bone marrow–bone marrow transplantation plus fetal thymus transplantation

Thymic function decreases in line with tumor progression in patients with cancer, resulting in immunodeficiency and a poor prognosis. In the present study, we attempted to restore thymic function by BALB/c (H-2^d) syngeneic (Syn), or B6 (H-2^b) allogeneic (Allo) bone marrow transplantation (BMT) using intra-bone marrow–bone marrow transplantation (IBM–BMT) plus Syn-, Allo- or C3H (H-2^k) 3rd-party fetal thymus transplantation (TT). Although the BALB/c mice with advanced tumors (Meth-A sarcoma; H-2^d, >4 cm²) treated with either Syn- or Allo-BMT alone showed a slight improvement in survival compared with non-treated controls, the mice treated with BMT + TT showed a longer survival. The mice treated with Allo-BMT + Allo-TT or 3rd-party TT showed the longest survival. Interestingly, although there was no difference in main tumor size among the BMT groups, lung metastasis was significantly inhibited by Allo-BMT + Allo-TT or 3rd-party TT. Numbers of CD4⁺ and CD8⁺ T cells, Con A response, and IFN-γ production increased significantly, whereas number of Gr-1⁺/CD11b⁺ myeloid suppressor cells and the percentage of FoxP3⁺ cells in CD4⁺ T cells significantly decreased in these mice. Furthermore, there was a positive correlation between survival days and the number of T cells or T cell function, while there was a negative correlation between survival days and lung metastasis, the number of Gr-1⁺/CD11b⁺ cells, or the percentage of FoxP3⁺ cells. These results suggest that BMT + TT, particularly Allo-BMT + Allo-TT or 3rd-party TT, is most effective in prolonging survival as a result of the restoration of T cell function in hosts with advanced tumors.     

Potential gene flow in natural populations of the Drosophila ananassae species cluster inferred from a nuclear mitochondrial pseudogene

A pseudogene with 94% similarity to mitochondrial cytochrome c oxidase subunit I (COI) was identified and localized to chromosome 4 of Drosophila ananassae. Because this chromosome is believed to have reduced recombination, its history can be traced using the pseudo-COI sequence. Pseudo-COI sequences were obtained from 27 iso-female lines of six taxa belonging to the D. ananassae species cluster in which reproductive isolation is incomplete. The phylogenetic network constructed from seven recognized haplotypes (#0-#6) indicated that different taxa inhabiting the same geographic area share the haplotypes: #1 from Papua New Guinean populations of D. ananassae and pallidosa-like-Wau; #2 from Papua New Guinean populations of D. ananassae, pallidosa-like, and papuensis-like; and #4 from South Pacific populations of D. ananassae and D. pallidosa. Taxon-K has a unique haplotype (#6), and 18 mutation steps separate it from the closest haplotype, #2. We discuss the possibility of chromosome 4 introgression beyond taxon boundaries.     

BAC library construction and BAC end sequencing of five Drosophila species: the comparative map with the D. melanogaster genome

We constructed and characterized arrayed bacterial artificial chromosome (BAC) libraries of five Drosophila species (D. melanogaster, D. simulans, D. sechellia, D. auraria, and D. ananassae), which are genetically well characterized in the studies of meiosis, evolution, population genetics, and developmental biology. The BAC libraries comprise 8,000 to 12,500 clones for each species, estimated to cover the most of the genomes. We sequenced both ends of most of these BAC clones with a success rate of 91%. Of these, 53,701 clones consisting of non-repetitive BAC end sequences (BESs) were mapped with reference of the public D. melanogaster genome sequences. The BES mapping estimated that the BAC libraries of D. auraria and D. ananassae covered 47% and 57% of the D. melanogaster genome, respectively, and those of D. melanogaster, D. sechellia, and D. simulans covered 94-97%. The low coverage by BESs of D. auraria and D. ananassae may be due to the high sequence divergence with D. melanogaster. From the comparative BES mapping, 111 possible breakpoints of chromosomal rearrangements were identified in these four species. The breakpoints of the major chromosome rearrangement between D. simulans and D. melanogaster on the third chromosome were determined within 20 kb in 84E and 30 kb in 93E/F. Corresponding breakpoints were also identified in D. sechellia. The BAC clones described here will be an important addition to the Drosophila genomic resources.     

IL-17 enhances the net angiogenic activity and in vivo growth of human non-small cell lung cancer in SCID mice through promoting CXCR-2-dependent angiogenesis

In this study, we examined the biological action of IL-17 on human non-small cell lung cancer (NSCLC). Although IL-17 had no direct effect on the in vitro growth rate of NSCLC, IL-17 selectively augmented the secretion of an array of angiogenic CXC chemokines, including CXCL1, CXCL5, CXCL6, and CXCL8 but not angiostatic chemokines, by three different NSCLC lines. Endothelial cell chemotactic activity (as a measure of net angiogenic potential) was increased in response to conditioned medium from NSCLC stimulated with IL-17 compared with those from unstimulated NSCLC. Enhanced chemotactic activity was suppressed by neutralizing mAb(s) to CXCL1, CXCL5, and CXCL8 or to CXCR-2 but not to vascular endothelial growth factor-A. Transfection with IL-17 into NSCLC had no effect on the in vitro growth, whereas IL-17 transfectants grew more rapidly compared with controls when transplanted in SCID mice. This IL-17-elicited enhancement of NSCLC growth was associated with increased tumor vascularity. Moreover, treatment with anti-mouse CXCR-2-neutralizing Ab significantly attenuated the growth of both neomycin phosphotransferase gene-transfected and IL-17-transfected NSCLC tumors in SCID mice. A potential role for IL-17 in modulation of the human NSCLC phenotype was supported by the findings that, in primary NSCLC tissues, IL-17 expression was frequently detected in accumulating and infiltrating inflammatory cells and that high levels of IL-17 expression were associated with increased tumor vascularity. These results demonstrate that IL-17 increases the net angiogenic activity and in vivo growth of NSCLC via promoting CXCR-2-dependent angiogenesis and suggest that targeting CXCR-2 signaling may be a novel promising strategy to treat patients with NSCLC.     

Molecular cloning of a novel immunoglobulin superfamily gene preferentially expressed by brain and testis

We have cloned and characterized a novel gene from both human and mouse that encodes a new member of the immunoglobulin superfamily. The gene is preferentially expressed in both brain and testis, and hence, termed BT-IgSF (brain- and testis-specific immunoglobulin superfamily). The predicted protein consists of V-type and C2-type immunoglobulin domains as well as a hydrophobic signal sequence, a single transmembrane region, and a cytoplasmic domain. Human BT-IgSF protein (431 amino acids) is 88% identical to the mouse protein (428 amino acids) and both show significant homology to coxsackie and adenovirus receptor (CAR) and endothelial cell-selective adhesion molecule (ESAM). We examined the expression of BT-IgSF with various cultured cells and found that the gene was expressed in both neurons and glial cells in vitro. Furthermore, the expression was preferentially detected in pyramidal cell layers of the dentate gyrus and hippocampus and in commissure fibers of the corpus callosum, in brain tissue sections examined. These findings suggest that BT-IgSF plays a role in the development or function of the central nervous system.     

Search for species-specific mating signal in courtship songs of sympatric sibling species,Drosophila ananassae and D. pallidosa

Sexual isolation is one of the most important mechanisms that may lead to speciation. Drosophila ananassae and D. pallidosa are useful for the study of sexual isolation, because of their sympatric distribution and no postmating isolation between them. Courtship songs are considered to play a crucial role in sexual isolation between D. ananassae and D. pallidosa. We recorded and analyzed male courtship songs of D. ananassae and D. pallidosa for eight and four geographical strains, respectively. Courtship behaviors of the two species were consistent with those previously described, however, male's middle leg shaking, which had not before been described, was observed in both species. Males sing by wing vibration only during courtship. Their song oscillograms were distinct between species, but those of conspecific strains were very similar, in spite of their different geographical derivation. We found species-specificity in burst length, pulse length, cycle number in a pulse, and frequency spectra of bursts; these results suggest that these song parameters may play a role in mate recognition that enforces their sexual isolation. The specific values of interpulse interval, cycle number in a pulse and intrapulse frequency were involved with the determination of specificity in frequency spectra of bursts. We discussed the possibility that the specific frequency spectra of bursts are recognized by females as the species-specific signal rather than each parameter individually.