The Participation of Speract in the Acrosome Reaction of Hemicentrotus pulcherrimus

A speract-free macromolecular fraction was prepared from the egg jelly of the sea urchin Hemicentrotus pulcherrimus by gel filtration and tested for ability to induce the acrosome reaction in H. pulcherrimus spermatozoa with or without exogenously added synthetic speract. The macromolecular fraction without speract showed only about half the activity of the original unfractionated jelly for induction of the acrosome reaction. The rates of the acrosome reaction induced by the fraction with speract were comparable with those induced by the unfractionated jelly at all pHs tested. Speract itself, however, did not induce the acrosome reaction in the absence of the macromolecular fraction of jelly. The acrosome reaction was associated with incerase of the cyclic AMP concentration in sperm cells, the extent of incerase depending on the concentration of the macromolecular fraction. Addition of speract to the fraction enhanced both induction of the acrosome reaction and increase in the cyclic AMP concentration induced by the fraction. These results suggest that a major factor(s) responsible for the acrosome reaction is a macromolecular component(s) of the jelly and that speract promotes the reaction as a co-factor.     

Colocasiomyia (Diptera: Drosophilidae) revised phylogenetically,with a new species group having peculiar lifecycles on monsteroid (Araceae) host plants

The phylogeny of Colocasiomyia (Drosophilidae) is analysed using data for 70 morphological characters, many of which are re‐evaluated from or added to those used previously, for an expanded taxon sample of 24 Colocasiomyia ingroup species. A special focus is put on three species, of which two have remained unresolved for their relationships to other Colocasiomyia species, and the other is a newly discovered species. The analysis results in a single, most parsimonious cladogram, in which a clade comprising the three focal species is recognized along with other clades recovered for the known species groups of Colocasiomyia. Based on this, a new species group—the gigantea group—is established, including Colocasiomyia gigantea (Okada), C. rhaphidophorae Gao & Toda, n.sp. and C. scindapsae Fartyal & Toda, n.sp. These species of the gigantea group breed on inflorescences/infructescences of the subfamily Monsteroideae (Araceae) exceptionally among Colocasiomyia species, most of which use plants of the subfamily Aroideae as their hosts. Colocasiomyia gigantea uses Epipremnum pinnatum (L.) Engler, C. rhaphidophorae uses Rhaphidophora hookeri Schott and C. scindapsae uses Scindapsus coriaceus Engler as their hosts. The host plants of the gigantea group are epiphytes and differ in the structure of spadix and the fruiting process from those of the Aroideae. To understand how the species of the gigantea group adapt to properties of their host plants, their reproductive ecology—most intensively that of C. gigantea—is investigated. The lifecycle of C. gigantea is characterized by its relatively slow embryonic development (taking approximately 6 days), the very long duration of the full‐grown first instar within the egg capsule (approximately three months) until dehiscence of host infructescence, and its relatively fast larval and pupal development (taking approximately 11 or 12 days). Some morphological adaptations and the reproductive strategy in terms of ‘egg size vs. number’ trade‐off are discussed in relation to their reproductive habits and peculiar lifecycles.     

Population structure of wild wheat D‐genome progenitor Aegilops tauschii Coss.: implications for intraspecific lineage diversification and evolution of common wheat

Aegilops tauschii Coss. is the D‐genome progenitor of hexaploid wheat. Aegilops tauschii, a wild diploid species, has a wide natural species range in central Eurasia, spreading from Turkey to western China. Amplified fragment length polymorphism (AFLP) analysis using a total of 122 accessions of Ae. tauschii was conducted to clarify the population structure of this widespread wild wheat species. Phylogenetic and principal component analyses revealed two major lineages in Ae. tauschii. Bayesian population structure analyses based on the AFLP data showed that lineages one (L1) and two (L2) were respectively significantly divided into six and three sublineages. Only four out of the six L1 sublineages were diverged from those of western habitats in the Transcaucasia and northern Iran region to eastern habitats such as Pakistan and Afghanistan. Other sublineages including L2 were distributed to a limited extent in the western region. Subspecies strangulata seemed to be differentiated in one sublineage of L2. Among three major haplogroups (HG7, HG9 and HG16) previously identified in the Ae. tauschii population based on chloroplast variation, HG7 accessions were widely distributed to both L1 and L2, HG9 accessions were restricted to L2, and HG16 accessions belonged to L1, suggesting that HG9 and HG16 were formed from HG7 after divergence of the first two lineages of the nuclear genome. These results on the population structure of Ae. tauschii and the genealogical relationship among Ae. tauschii accessions should provide important agricultural and evolutionary knowledge on genetic resources and conservation of natural genetic diversity.     

Evidence for contribution of autophagy to Rubisco degradation during leaf senescence in Arabidopsis thaliana

During leaf senescence, Rubisco is gradually degraded and its components are recycled within the plant. Although Rubisco can be mobilized to the vacuole by autophagy via specific autophagic bodies, the importance of this process in Rubisco degradation has not been shown directly. Here, we monitored Rubisco autophagy during leaf senescence by fusing synthetic green fluorescent protein (sGFP) or monomeric red fluorescent protein (mRFP) with Rubisco in Arabidopsis (Arabidopsis thaliana). When attached leaves were individually exposed to darkness to promote their senescence, the fluorescence of Rubisco‐sGFP was observed in the vacuolar lumen as well as chloroplasts. In addition, release of free‐sGFP due to the processing of Rubisco‐sGFP was observed in the vacuole of individually darkened leaves. This vacuolar transfer and processing of Rubisco‐sGFP was not observed in autophagy‐deficient atg5 mutants. Unlike sGFP, mRFP was resistant to proteolysis in the leaf vacuole of light‐grown plants. The vacuolar transfer and processing of Rubisco‐mRFP was observed at an early stage of natural leaf senescence and was also obvious in leaves naturally covered by other leaves. These results indicate that autophagy contributes substantially to Rubisco degradation during natural leaf senescence as well as dark‐promoted senescence.     

A seed parasitoid wasp prevents berries from changing their colour,reducing their attractiveness to frugivorous birds

1. Frugivorous and seed‐feeding insects may alter the traits of fruits, such as shape and size, which may influence fruit attractiveness to frugivorous birds. Consequently, trait‐mediated interactions may occur in systems where plants, seed‐dispersing frugivorous vertebrates, and frugivorous or seed‐feeding insects interact. We investigated colour manipulation in Ilex integra Thunb. berries caused by the seed parasitoid wasp Macrodasyceras hirsutum Kamijo and how that manipulation relates to fruit attractiveness for frugivorous birds. 2. In winter, the colour of I. integra berries varied from green to red, but most berries were greenish, indicating that the berries were immature. Berry dissection indicated that the number of live parasitoid larvae present within each berry was closely related to berry colour – the greater the number of live larvae, more intense is the green colour of the berry. However, the wasp larvae did not modify the shape or size of the berries. More than 98% of berries that were protected from the insects by gauze bags ripened and turned red. In the present study, berries with unfertilised seeds alone turned red. Field‐feeding preference tests showed that the brown‐eared bulbul Hypsipetes amaurotis Temminck preferred red berries to green berries. 3. We demonstrated that the seed parasitoid wasp manipulates the berry colour, but not its shape or size, in a density‐dependent manner. Because green berries suffered less from bird foraging, we believe that this colour manipulation helps the wasps to avoid being killed by the birds. The present study indicates that manipulation by wasps may reduce the level of mutualism between the tree and seed‐dispersing birds.     

Linking the spatio‐temporal distribution of an edaphic crane fly to its heterogeneous soil environment

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Phylogeny and classification of Colocasiomyia (Diptera, Drosophilidae), and its evolution of pollination mutualism with aroid plants

Abstract Colocasiomyia, a moderate‐sized genus in the subfamily Drosophilinae, comprises seventy (twenty‐six described and forty‐four undescribed) species. Several Colocasiomyia species have evolved intimate mutualisms with specific host plants, especially of the family Araceae: the flies depend throughout the entire life cycle, oviposition, larval growth, pupation, and adult feeding and mating, on inflorescences of their host plants, and in turn act as species‐specific pollinators for their host plants. To understand the evolution of this mutualism between Colocasiomyia flies and their host plants, the phylogenetic relationships of this genus and some possibly related taxa are inferred from a cladistic analysis based on sixty‐two characters of adult morphology. We conclude that Colocasiomyia is polyphyletic, with the C. arenga species group clearly separate. Colocasiomyia without the arenga group (Colocasiomyia proper) is sister to all other studied drosophilines, whereas the arenga group is relatively derived within the Drosophilinae. Within Colocasiomyia proper, four clades are recognized, three of which correspond to previously proposed species groups: the cristata, toshiokai and baechlii groups. The other clade, C. sp.1 aff. nepalensis+C. sp.2 aff. nepalensis, is defined as a new species group. Relationships amongst the four clades and three independent species (C. micheliae, C. gigantea and C. sp.K1) remain almost unresolved, except for a sister group relationship between the toshiokai and baechlii groups. The classification of species groups in Colocasiomyia is revised by erecting two new species groups (crassipes and zeylanica groups) in addition to the three known (baechlii, cristata and toshiokai) groups. Revision of the arenga group, which should be removed from Colocasiomyia, is left for future studies. The evolution of host plant selection in Colocasiomyia is discussed by mapping host plant taxa (families, subfamilies and tribes) on the phylogenetic tree deduced from the cladistic analysis. Cohabitation in the same host inflorescence by a pair of species with microallopatric niche separation on the spadix is hypothesized to have evolved independently at least more than twice in Colocasiomyia.