Chrysophyllum marginatum (Sapotaceae): Generalist pollination and cryptic gynomonoecious

Chrysophyllum (Chrysophylloideae, Chrysophylleae) is the second largest genus in the Sapotaceae. Studies of pollination ecology in this genus are non-existent, although there are records of entomophily for this family. Considering the lack of detailed studies on pollination ecology and sexual systems in Chrysophyllum species, we investigate the floral morphology and biology and floral visitors of Chrysophyllum marginatum to verify which sexual system is present in the studied population and whether flowers of this species are visited and pollinated by different insect groups. The population of C. marginatum has weak and cryptic gynomonoecy because the plants produce a low percentage of functionally pistillate flowers (4.2%) and these flowers appear to be perfect flowers (hermaphrode). Flowers of C. marginatum are phenotypically, ecologically and functionally generalist because: (a) they are actinomorphic, open and not restrictive in terms of access to floral resources; (b) they are visited by 26 species of insects that are potential pollinators; and (c) among these species several groups can be effective pollinators, mainly bees and flies, according to the most effective pollinator principle. We consider bees and flies to be the main pollinator group of C. marginatum, due to their high visitation rate, richness and intrafloral visiting behavior, and because they especially forage among plant individuals and are able to promote xenogamy. Nectaries were found in the ovary base and osmophores in the petal margins, as floral attractants. For Chrysophyllum, this is the first record of gynomonoecy and for the family this is considered the second record. Chrysophyllum marginatum has generalist and entomophilous pollination, as recorded in other Sapotaceae Neotropical species.     

Expression cassette and plasmid construction for Yeast Surface Display in Saccharomyces cerevisiae

Objectives

Develop a Cell Surface Display system in Saccharomyces cerevisiae, based on the construction of an expression cassette for pYES2 plasmid.

Results

The construction of an expression cassette containing the α-factor signal peptide and the C-terminal portion of the α-agglutinin protein was made and its sequence inserted into a plasmid named pYES2/gDαAgglutinin. The construction allows surface display of bovine herpesvirus type 5 (BoHV-5) glycoprotein D (gD) on S. cerevisiae BY4741 strain. Recombinant protein expression was confirmed by dot blot, and indirect immunofluorescence using monoclonal anti-histidine antibodies and polyclonal antibodies from mice experimentally vaccinated with a recombinant gD.

Conclusions

These results demonstrate that the approach and plasmid used represent not only an effective system for immobilizing proteins on the yeast cell surface, as well as a platform for immunobiologicals development.

     

Book reviews

Book reviewed in this article: Fruit flies, their biology, natural enemies and control. Volume A. A.S. Robinson and G.H.S. Hooper (eds.). Martin R. Speight and David Wainhouse: Ecology and Management of Forest Insects.     

Quantitative profiling of axonal guidance proteins during the differentiation of human neurospheres

Axon guidance is required for the establishment of brain circuits. Whether much of the molecular basis of axon guidance is known from animal models, the molecular machinery coordinating axon growth and pathfinding in humans remains to be elucidated. The use of induced pluripotent stem cells (iPSC) from human donors has revolutionized in vitro studies of the human brain. iPSC can be differentiated into neuronal stem cells which can be used to generate neural tissue-like cultures, known as neurospheres, that reproduce, in many aspects, the cell types and molecules present in the brain. Here, we analyzed quantitative changes in the proteome of neurospheres during differentiation. Relative quantification was performed at early time points during differentiation using iTRAQ-based labeling and LC-MS/MS analysis. We identified 6438 proteins, from which 433 were downregulated and 479 were upregulated during differentiation. We show that human neurospheres have a molecular profile that correlates to the fetal brain. During differentiation, upregulated pathways are related to neuronal development and differentiation, cell adhesion, and axonal guidance whereas cell proliferation pathways were downregulated. We developed a functional assay to check for neurite outgrowth in neurospheres and confirmed that neurite outgrowth potential is increased after 10 days of differentiation and is enhanced by increasing cyclic AMP levels. The proteins identified here represent a resource to monitor neurosphere differentiation and coupled to the neurite outgrowth assay can be used to functionally explore neurological disorders using human neurospheres as a model.     

Etioplasts with protochlorophyll and protochlorophyllide forms in the under‐soil epicotyl segments of pea (Pisum sativum) seedlings grown under natural light conditions

To study if etiolation symptoms exist in plants grown under natural illumination conditions, under‐soil epicotyl segments of light‐grown pea (Pisum sativum) plants were examined and compared to those of hydroponically dark‐grown plants. Light‐, fluorescence‐ and electron microscopy, 77 K fluorescence spectroscopy, pigment extraction and pigment content determination methods were used. Etioplasts with prolamellar bodies and/or prothylakoids, protochlorophyll (Pchl) and protochlorophyllide (Pchlide) forms (including the flash‐photoactive 655 nm emitting form) were found in the (pro)chlorenchyma of epicotyl segments under 3 cm soil depth; their spectral properties were similar to those of hydroponically grown seedlings. However, differences were found in etioplast sizes and Pchlide:Pchl molar ratios, which indicate differences in the developmental rates of the under‐soil and of hydroponically developed cells. Tissue regions closer to the soil surface showed gradual accumulation of chlorophyll, and in parallel, decrease of Pchl and Pchlide. These results proved that etioplasts and Pchlide exist in soil‐covered parts of seedlings even if they have a 3–4‐cm long photosynthetically active shoot above the soil surface. This underlines that etiolation symptoms do develop under natural growing conditions, so they are not merely artificial, laboratory phenomena. Consequently, dark‐grown laboratory plants are good models to study the early stages of etioplast differentiation and the Pchlide–chlorophyllide phototransformation.     

Chlorophyll a fluorescence and ultrastructural changes in chloroplast of water hyacinth as indicators of environmental stress

Chlorophyll a fluorescence parameters and transmission electron microscopy (TEM) were used to assess the stress conditions in water hyacinth along the Paraíba do Sul River (PSR), an important River in southeastern Brazil. The data were obtained at the end of the dry season of 2005 and at the end of the wet season of 2006. Changes in F₀ and F_m parameters were observed as differentiated responses, depending on the season. Non-photochemical dissipation (qN and NPQ) from plants was greater in the most industrialized region of the PSR in both seasons. However, F_v/F_m for all samples ranged between 0.77 and 0.81, showing that high maximum quantum yield was maintained. Although the F_v/F_m suggests that the plants were exhibiting normal photochemical activities, ultrastructural changes in chloroplasts showed thylakoids disorganization. Plants from the most industrialized region showed non-stacking grana thylakoids disposition. In spite of these alterations, the membrane integrity was maintained, suggesting an adaptation to adjustment to adverse environmental conditions.     

Female‐targeted attractant containing pear ester for Synanthedon myopaeformis

When testing pear ester (ethyl‐2,4‐decadienoate) + acetic acid (PEAA) lures to catch codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in Hungary, significant catches of the apple clearwing moth, Synanthedon myopaeformis (Borkhausen) (Lepidoptera: Sesiidae), were also recorded. This sesiid is one of the most important pests of apple in Europe. Pear ester plus acetic acid lures were attractive to S. myopaeformis no matter whether the two compounds were provided in separate dispensers or mixed together in a single dispenser, and a large percentage (40–80%) of the clearwing moths caught were females. In all cases, traps baited with binary combinations of PEAA caught far more than traps baited with either of the compounds presented alone. Traps with PEAA lures in some tests caught (females and males together) up to ca. 20% of the catch in traps baited with the synthetic apple clearwing moth sex attractant (all males). Consequently, the PEAA lure shows potential for future practical applications as a female‐targeted lure. To our knowledge, this is the first report of attractiveness of a lure containing pear ester for non‐tortricid Lepidoptera. Our finding suggests that the compound may be exploited as a host location stimulus by a wider array of insects than was indicated previously.