Complex life cycles of multicellular eukaryotes: new approaches based on the use of model organisms

A wide variety of life cycles can be found in the different groups of multicellular eukaryotes. Here we provide an overview of this variety, and review some of the theoretical arguments that have been put forward to explain the evolutionary stability of different life cycle strategies. We also describe recent progress in the analysis of the haploid-diploid life cycle of the model angiosperm Arabidopsis thaliana and show how new molecular data are providing a means to test some of the theoretical predictions. Finally, we describe an emerging model organism from the brown algae, Ectocarpus siliculosus, and highlight the potential of this system for the investigation of the mechanisms that regulate complex life cycles.     

Recent decrease in chinstrap penguin (<Emphasis Type="Italic">Pygoscelis antarctica</Emphasis>) populations at two of Admiralty Bay’s islets on King George Island,South Shetland Islands,Antarctica

We examined the breeding populations of chinstrap penguins (Pygoscelis antarctica) on Chabrier Rock and Shag Island within Admiralty Bay, King George Island, South Shetland Islands, Antarctica from 2002 to 2004. When comparing our results to historic data from 1979, we found an overall decline of 57% in the last 25 years, mirroring the population trend of this species in other regions of the Antarctic Peninsula. Our results are discussed in relation to factors hypothesized to be driving the declines found at other sites, as well as the importance of consistent annual censuses to accurately determine population trends.     

Life cycle assessment of a multi-material car component

Background, Aims and Scope In recent years, the automotive industry has been experiencing an increasing concern with environmental requirements. A particular focus is being given to light-weighting of cars, to reducing fuel consumption and to the use of different recycling materials. Consequently, decisions on product design and development must involve economic and technological as well as environmental considerations. In adequate conditions, the LCA methodology enables one to assist an effective integration of the environmental considerations in the decision-making process [1]. In this paper, a multi-material car component which is part of the current automotive brake system, has been modified by its original manufacturer. Such a modification included the use of a new multi-material injection moulding process and the consumption of recyclable materials. The new and the current component were comparatively assessed throughout their life cycles in order to evaluate their respective environmental impacts and, thus, to verify if the new component offers a lower environmental load. The results described in this paper are part of the outcome of a broader research project involving industrial companies, university, technological centres and research institutes based in Portugal, Spain and Germany. Main Features The car component under focus has four subcomponents whose base materials consist of steel and plastic. The LCA methodology is used to evaluate two scenarios describing the new car component, on the one hand, and the reference scenario, which consists of the existing car component, on the other. The former results from the selection of new subcomponents materials, aiming to use a new production process together with a recycling strategy. Results and Discussion The inventory analysis shows a lower energy consumption in the alternative scenario (4.2 MJ) compared to the reference scenario (6.1 MJ). Most of that energy is still non-renewable, relating in particular to crude consumption in the car use phase and in the production phase (transports and plastics production). The life cycle inventory analysis indicates also that the alternative scenario has lower air emissions of CO₂, CO, NO_x, SO_x, NM VOC and PM10, as well as lower solid wastes and water emissions of oils and BOD5. Otherwise, the water emissions of undissolved substances and COD are higher for the alternative scenario. Most of the energy consumed and the air pollutants inventoried occur as a consequence of the use phase. Otherwise, for most of the life cycle water emissions inventoried and solid wastes, the production phase is the major contributor. The impact assessment, performed with the CML method, allows one to conclude that the alternative scenario exhibits lower results in all the impact categories. Both scenarios have similar environmental profiles, being: (i) the use phase, the major contributor for the abiotic depletion, global warming, photochemical oxidation, acidification and eutrophication; and (ii) the production phase, the main contributor for ozone depletion, human toxicity, fresh water aquatic ecotoxicity, marine aquatic ecotoxicity and terrestrial ecotoxicity. The sensitivity analysis, with respect to the fuel consumption reduction value, the impact assessment method and the final disposal scenario, performed in this study allows one to confirm, as a main conclusion, that the alternative scenario is environmentally preferable to the reference scenario. Conclusion The results obtained through the application of the LCA methodology enable one to conclude that the alternative component has a lower environmental load than the reference component. Recommendations and Perspectives Considering that the time required for the inventory data collection is a critical issue in LCA practise, the insights provided by this particular case study are likely to be useful to product developers in the car component manufacturing industry, particularly to brake system manufacturers supporting the environmental design within the sector.     

Biological parameters and damage by Macrosoma tipulata Hübner (Lepidoptera: Hedylidae), in cupuaçu tree [Theobroma grandiflorum (Wild ex Spreng Schum)] in Amazonas, Brazil

Biological aspects of the caterpillar Macrosoma tipulata Hübner and its damage to young leaves of Theobroma grandiflorum (Wild ex Spreng Schum) were studied under laboratory conditions of 24.5 +/- 0.7 masculineC, UR 61.6 +/- 9.1% and 12h photophase. The larval stage presented five instars with a total duration of 15.9 +/- 4.31 days, and survival of 98%. The pupal period stage was 7.0 +/- 0.56 days for males and 6.9 +/- 0.56 days for females, with 99% survival for both sex. The pupal mean length was 18.9 +/- 0.89 mm for males and 19.1 +/- 1.13 mm for females. The mean longevity of the adult was 10.3 +/- 2.25 days. The vertical distribution of damage was relatively uniform, with a tendency of greater defoliation in the middle of the treetop, but without significant difference among the three positions.     

Effect of Cu2+ and Zn2+ ions in Ca-ATPase activity isolated from Pachymerus nucleorum (Fabricius) (Coleoptera: Chrysomelidae, Bruchinae) larvae

ATPases, an important target of insecticides, are enzymes that hydrolyze ATP and use the energy released in that process to accomplish some type of cellular work. Pachymerus nucleorum (Fabricius) larvae possess an ATPase, that presents high Ca-ATPase activity, but no Mg-ATPase activity. In the present study, the effect of zinc and copper ions in the activity Ca-ATPase of that enzyme was tested. More than 90% of the Ca-ATPase activity was inhibited in 0.5 mM of copper ions or 0.25 mM of zinc ions. In the presence of EDTA, but not in the absence, the inhibition by zinc was reverted with the increase of calcium concentration. The inhibition by copper ions was not reverted in the presence or absence of EDTA. The Ca-ATPase was not inhibited by treatment of the ATPase fraction with copper, suggesting that the copper ion does not bind directly to the enzyme. The results suggest that zinc and copper ions form a complex with ATP and bind to the enzyme inhibiting its Ca-ATPase activity.     

Insecticidal action of Annona coriacea lectin against the flour moth Anagasta kuehniella and the rice moth Corcyra cephalonica (Lepidoptera: Pyralidae)

Annona coriacea lectin (ACLEC) was tested for insecticidal activity against larvae of two pyralid moths, Anagasta kuehniella and Corcyra cephalonica. ACLEC produced approximately 50% mortality and mass loss in A. kuehniella larvae when incorporated into an artificial diet at levels of 1.5% and 1.0% (w/w), respectively. In contrast, the inclusion of up to 2% ACLEC in the diet did not significantly decrease the survival or weight of C. cephalonica larvae. The nutritional indices for A. kuehniella and C. cephalonica suggested that ACLEC had a multi-mechanistic mode of action and was an antifeedant for both insects. The toxicity in A. kuehniella apparently resulted from a change in the gut membrane environment and consequent disruption of digestive enzyme recycling mechanisms. Affinity chromatography showed that ACLEC bound to midgut proteins of A. kuehniella and C. cephalonica. However, the 14 kDa subunit of ACLEC was not digested by midgut proteases of A. kuehniella, but was degraded by the corresponding C. cephalonica proteases within a few hours. These findings suggest the possibility of using ACLEC to engineer crop plants.     

Weight–length and length–length relationships for reef fish species from the Cape Verde Archipelago (tropical north‐eastern Atlantic)

This study reports weight–length and length–length relationships for selected coastal reef fish species of the Cape Verde Archipelago (tropical north‐eastern Atlantic). Specimens were caught with different types of gear (long‐lines, hand‐lines, purse‐seines and traps) during commercial fishing activities and sampled during fish market operations. A total of 8328 individuals were sampled, representing 29 species from 14 Families. This study provides the first references on weight–length and length–length relationships for five and 23 fish species worldwide, for 10 and 24 species for the Eastern Atlantic and for 12 and 26 species for Cape Verde Archipelago, respectively. Additionally, it provides revised weight–length relationships for 11 species from Cape Verde waters.     

microRNAs and the evolution of complex multicellularity: identification of a large,diverse complement of microRNAs in the brown alga Ectocarpus

There is currently convincing evidence that microRNAs have evolved independently in at least six different eukaryotic lineages: animals, land plants, chlorophyte green algae, demosponges, slime molds and brown algae. MicroRNAs from different lineages are not homologous but some structural features are strongly conserved across the eukaryotic tree allowing the application of stringent criteria to identify novel microRNA loci. A large set of 63 microRNA families was identified in the brown alga Ectocarpus based on mapping of RNA-seq data and nine microRNAs were confirmed by northern blotting. The Ectocarpus microRNAs are highly diverse at the sequence level with few multi-gene families, and do not tend to occur in clusters but exhibit some highly conserved structural features such as the presence of a uracil at the first residue. No homologues of Ectocarpus microRNAs were found in other stramenopile genomes indicating that they emerged late in stramenopile evolution and are perhaps specific to the brown algae. The large number of microRNA loci in Ectocarpus is consistent with the developmental complexity of many brown algal species and supports a proposed link between the emergence and expansion of microRNA regulatory systems and the evolution of complex multicellularity.     

Rab27a controls HIV-1 assembly by regulating plasma membrane levels of phosphatidylinositol 4,5-bisphosphate

During the late stages of the HIV-1 replication cycle, the viral polyprotein Pr55^Gag is recruited to the plasma membrane (PM), where it binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) and directs HIV-1 assembly. We show that Rab27a controls the trafficking of late endosomes carrying phosphatidylinositol 4-kinase type 2 α (PI4KIIα) toward the PM of CD4⁺ T cells. Hence, Rab27a promotes high levels of PM phosphatidylinositol 4-phosphate and the localized production of PI(4,5)P₂, therefore controlling Pr55^Gag membrane association. Rab27a also controls PI(4,5)P₂ levels at the virus-containing compartments of macrophages. By screening Rab27a effectors, we identified that Slp2a, Slp3, and Slac2b are required for the association of Pr55^Gag with the PM and that Slp2a cooperates with Rab27a in the recruitment of PI4KIIα to the PM. We conclude that by directing the trafficking of PI4KIIα-positive endosomes toward the PM, Rab27a controls PI(4,5)P₂ production and, consequently, HIV-1 replication.