CD36 homolog divergence is responsible for the selectivity of carotenoid species migration to the silk gland of the silkworm Bombyx mori

Dietary carotenoids are absorbed in the intestine and delivered to various tissues by circulating lipoproteins; however, the mechanism underlying selective delivery of different carotenoid species to individual tissues remains elusive. The products of the Yellow cocoon (C) gene and the Flesh (F) gene of the silkworm Bombyx mori determine the selectivity for transport of lutein and β-carotene, respectively, to the silk gland. We previously showed that the C gene encodes Cameo2, a CD36 family member, which is thought to function as a transmembrane lipoprotein receptor. Here, we elucidated the molecular identity of the F gene product by positional cloning, as SCRB15, a paralog of Cameo2 with 26% amino acid identity. In the F mutant, SCRB15 mRNA structure was severely disrupted, due to a 1.4 kb genomic insertion in a coding exon. Transgenic expression of SCRB15 in the middle silk gland using the binary GAL4-UAS expression system enhanced selective β-carotene uptake by the middle silk gland, while transgenic expression of Cameo2 enhanced selective lutein uptake under the same GAL4 driver. Our findings indicate that divergence of genes in the CD36 family determines the selectivity of carotenoid species uptake by silk gland tissue and that CD36-homologous proteins can discriminate among carotenoid species.     

Synthesis of (+)-aptosimon,a 4-oxofurofuran lignan,by erythro selective aldol condensation and stereoconvergent cyclization as the key reactions

The 4-oxofurofuran lignan, (+)-aptosimon (1), was synthesized from gamma-butyrolactone (9). To construct the two benzylic chiral center of (+)-aptosimon (1), highly erythro selective aldol condensation and stereoconvergent SN1 intramolecular cyclization were used as the key reactions.     

Wing base morphology of Aetalionidae (Hemiptera: Cicadomorpha) and its phylogenetic implications

The Aetalionidae is a small family belonging to the treehopper superfamily Membracoidea (Hemiptera: Cicadomorpha). Although the wing‐base morphology of Cicadomorpha was examined in detail recently, the wing base of this family has not been investigated to date. We examined morphology of the wing‐base structure of Aetalionidae. Using the characters selected from the wing base, we inferred the phylogenetic placement of this family and confirmed that it belongs to the superfamily Membracoidea and is likely a sister group of the Membracidae.     

Enamel matrix derivative is a potent inhibitor of breast cancer cell attachment to bone

This study examined whether enamel matrix derivative (EMD) inhibits the adhesion of cancer cells to bone. A typical breast cancer cell line, MCF-7, was used. Conditioned human osteosarcoma cell (Saos-2) medium was used as extracellular bone matrix (ECBM) to measure cell attachment. MCF-7 cells were incubated on ECBM-coated culture plates with or without soluble EMD, Arg-Gly-Asp (RGD) sequence blocking peptides, recombinant bone sialoprotein (rBSP), or specific integrin antibodies, and the attached cells were quantified using toluidine blue staining. EMD markedly reduced the attachment of MCF-7 cells to ECBM in a dose-dependent manner. An RGD peptide (GRGDSP) and recombinant BSP inhibited cell attachment to the same degree as EMD. Similarly, anti-alphavbeta3 integrin antibody strongly reduced cell attachment, whereas anti-alphavbeta5 and anti-beta1 integrin antibodies had less marked effects on cell attachment. These results show that EMD inhibits MCF-7 cell attachment to a bone matrix and that it might be useful as an anti-adhesive agent for breast cancer cells to bone in vivo.     

A CD36-related Transmembrane Protein Is Coordinated with an Intracellular Lipid-binding Protein in Selective Carotenoid Transport for Cocoon Coloration

The transport pathway of specific dietary carotenoids from the midgut lumen to the silk gland in the silkworm, Bombyx mori, is a model system for selective carotenoid transport because several genetic mutants with defects in parts of this pathway have been identified that manifest altered cocoon pigmentation. In the wild-type silkworm, which has both genes, Yellow blood (Y) and Yellow cocoon (C), lutein is transferred selectively from the hemolymph lipoprotein to the silk gland cells where it is accumulated into the cocoon. The Y gene encodes an intracellular carotenoid-binding protein (CBP) containing a lipid-binding domain known as the steroidogenic acute regulatory protein-related lipid transfer domain. Positional cloning and transgenic rescue experiments revealed that the C gene encodes Cameo2, a transmembrane protein gene belonging to the CD36 family genes, some of which, such as the mammalian SR-BI and the fruit fly ninaD, are reported as lipoprotein receptors or implicated in carotenoid transport for visual system. In C mutant larvae, Cameo2 expression was strongly repressed in the silk gland in a specific manner, resulting in colorless silk glands and white cocoons. The developmental profile of Cameo2 expression, CBP expression, and lutein pigmentation in the silk gland of the yellow cocoon strain were correlated. We hypothesize that selective delivery of lutein to specific tissue requires the combination of two components: 1) CBP as a carotenoid transporter in cytosol and 2) Cameo2 as a transmembrane receptor on the surface of the cells.     

Umami changes intracellular Ca2+ levels using intracellular and extracellular sources in mouse taste receptor cells

Recently, candidates for umami receptors have been identified in taste cells, but the precise transduction mechanisms of the downstream receptor remain unknown. To investigate how intracellular Ca(2+) increases in the umami transduction pathway, we measured changes in intracellular Ca(2+) levels in response to umami stimuli monosodium glutamate (MSG), IMP, and MSG + IMP in mouse taste receptor cells (TRCs) by Ca(2+) imaging. Even when extracellular Ca(2+) was absent, 1/3 of umami-responsive TRCs exhibited increased intracellular Ca(2+) levels. When intracellular Ca(2+) was depleted, half of the TRCs retained their response to umami. These results suggest that umami-responsive TRCs increase their intracellular Ca(2+) levels through two pathways: by releasing Ca(2+) from intracellular stores and by an influx of Ca(2+) from extracellular sources. We conclude that the Ca(2+) influx from extracellular source might play an important role in the synergistic effect between MSG and IMP.     

Head-plug defense in a gall aphid

The aphid Astegopteryx sp. forms a banana-bunch shaped gall consisting of several subgalls on Styrax benzoides in northern Thailand, and completes its life cycle on the tree, without migrating to secondary hostplants. We found that its soldiers had sclerotic, protruded heads with many spine-like setae, and that several soldiers cooperate to plug the ostiole of the subgall with these heads. Of 173 ostioles examined in the field, 90.8 % were plugged with no space among the guarding soldiers. Many eggs and sexuals were found within subgalls guarded by soldiers, and a number of males were found trying to intrude into these subgalls. However, they were blocked by guarding soldiers, and it was no easy task for them to intrude into subgalls. The same was true for some soldiers that had rushed out of the subgall. Guarding soldiers often prevented outside soldiers from coming back into the subgall. These findings suggest an interesting possibility that guarding soldiers might consequently select still active, reusable soldiers and strong males for sexual females in their subgall. Received 6 March 2005; revised 5 and 20 July 2005; accepted 27 July 2005.     

Phylogenetic relationships and convergent evolution of ocean‐shore ground beetles (Coleoptera: Carabidae: Trechinae: Bembidion and relatives)

Through phylogenetic analysis of seven genes, we show that there have been at least six independent entries into intertidal habitats in the history of bembidiine carabids, in the ancestors of: (i) Orzolina Machado, (ii) Bembidion (Desarmatocillenus Netolitzky), (iii) Bembidion laticeps (LeConte) + palosverdes Kavanaugh & Erwin, (iv) Bembidion laterale (Samouelle), (v) Bembidion umi Sasakawa and Bembidion quadriimpressum (Motschulsky) (which may represent two separate entries), and (vi) B. nigropiceum (Marsham). The following lineages are widely separated within the subtribe Bembidiina: Orzolina is sister to the genus Ocys Stephens; subgenus Desarmatocillenus appears to be sister to all Bembidion Latreille excluding subgenus Phyla Motschulsky; B. laticeps + B. palosverdes is a clade in the Bembidion series; B. laterale is a member of the Princidium Motschulsky complex; B. umi and B. quadriimpressum are related to the Nearctic Clade of the Ocydromus Clairville complex; B. nigropiceum is sister to B. praeustum Dejean among sampled species. There are three separate lineages of ocean‐shore bembidiines that are known to prey on amphipods, and adults of these lineages [Bembidion (Desarmatocillenus), B. laterale, and B. mandibulare Solier] have unusually wide heads with long mandibles. Also common among independent lineages restricted to ocean shores are prominent front angles of the prothorax, larger numbers of setae on the elytral disc, a notable sinuation in the margin of each elytron near its apex, and short, wide mesotarsi. The reasons for the repeated evolution of these features are not evident. Our results also suggest that inland species of the Nearctic Clade may have arisen from an ocean‐shore ancestor. The close genetic similarities between the gravel river shore dwelling B. praeustum and the intertidal specialist B. nigropiceum suggest that the striking morphological adaptations of B. nigropiceum to the intertidal zone arose rapidly. We make one nomenclatural change: we resurrect the subgenus Lymneops Casey to accommodate B. palosverdes and B. laticeps.     

Aminooxy‐naphthylpropionic acid and its derivatives are inhibitors of auxin biosynthesis targeting l‐tryptophan aminotransferase: structure–activity relationships

We previously reported l ‐α‐aminooxy‐phenylpropionic acid (AOPP) to be an inhibitor of auxin biosynthesis, but its precise molecular target was not identified. In this study we found that AOPP targets TRYPTOPHAN AMINOTRANSFERASE of ARABIDOPSIS 1 (TAA1). We then synthesized 14 novel compounds derived from AOPP to study the structure–activity relationships of TAA1 inhibitors in vitro. The aminooxy and carboxy groups of the compounds were essential for inhibition of TAA1 in vitro. Docking simulation analysis revealed that the inhibitory activity of the compounds was correlated with their binding energy with TAA1. These active compounds reduced the endogenous indole‐3‐acetic acid (IAA) content upon application to Arabidopsis seedlings. Among the compounds, we selected 2‐(aminooxy)‐3‐(naphthalen‐2‐yl)propanoic acid (KOK1169/AONP) and analyzed its activities in vitro and in vivo. Arabidopsis seedlings treated with KOK1169 showed typical auxin‐deficient phenotypes, which were reversed by exogenous IAA. In vitro and in vivo experiments indicated that KOK1169 is more specific for TAA1 than other enzymes, such as phenylalanine ammonia‐lyase. We further tested 41 novel compounds with aminooxy and carboxy groups to which we added protection groups to increase their calculated hydrophobicity. Most of these compounds decreased the endogenous auxin level to a greater degree than the original compounds, and resulted in a maximum reduction of about 90% in the endogenous IAA level in Arabidopsis seedlings. We conclude that the newly developed compounds constitute a class of inhibitors of TAA1. We designated them ‘pyruvamine’.     

Cryptic diversity,high host specificity and reproductive synchronization in army ant‐associated Vatesus beetles

Army ants and their arthropod symbionts represent one of the most species‐rich animal associations on Earth, and constitute a fascinating example of diverse host–symbiont interaction networks. However, despite decades of research, our knowledge of army ant symbionts remains fragmentary due to taxonomic ambiguity and the inability to study army ants in the laboratory. Here, we present an integrative approach that allows us to reliably determine species boundaries, assess biodiversity, match different developmental stages and sexes, and to study the life cycles of army ant symbionts. This approach is based on a combination of community sampling, DNA barcoding, morphology and physiology. As a test case, we applied this approach to the staphylinid beetle genus Vatesus and its different Eciton army ant host species at La Selva Biological Station, Costa Rica. DNA barcoding led to the discovery of cryptic biodiversity and, in combination with extensive community sampling, revealed strict host partitioning with no overlap in host range. Using DNA barcoding, we were also able to match the larval stages of all focal Vatesus species. In combination with studies of female reproductive physiology, this allowed us to reconstruct almost the complete life cycles of the different beetle species. We show that Vatesus beetles are highly adapted to the symbiosis with army ants, in that their reproduction and larval development are synchronized with the stereotypical reproductive and behavioural cycles of their host colonies. Our approach can now be used to study army ant‐symbiont communities more broadly, and to obtain novel insights into co‐evolutionary and ecological dynamics in species‐rich host–symbiont systems.