我国农田生态系统土壤动物生态学研究进展

综述了我国近30年来农田生态系统土壤动物生态学研究进展,概述了我国农田土壤动物的群落多样性及其地理分布,总结了农田生态系统中土壤动物对不同耕作方式、施肥和喷洒农药等农业措施、不同土地利用方式以及工业污染的响应,并就土壤动物对农田生态系统健康状况的指示作用等研究的相关进展进行了讨论.通过与国外相关领域的研究进行比较,指出目前研究中存在的问题,提出农田生态系统未来研究的一些热点问题及展望.     

Effect of fast-, medium- and slow-growing strains on meat quality of chickens reared under the organic farming method

The characteristics of meat quality, chemical and fatty acid composition, from fast-growing (FG) and medium-growing (MG) meat-type and slow-growing (SG) egg-type chickens reared under organic conditions were compared. Three-hundred and sixty 1-day-old male chicks, equally divided into three experimental groups represented by strains (FG: Cobb 700, MG: Naked neck Kabir and SG: Brown Classic Lohman) were housed into three poultry houses with outdoor pasture availability of 10 m(2)/bird located in the same Research Centre of the University of Perugia. All the birds were fed ad libitum the same diets formulated according to the European Union (EU) Regulations by using organic raw materials. Birds from the FG and MG groups were raised until 81 days, whereas birds from the SG group were raised until 96 days in order to achieve an acceptable market live weight. SG birds showed significantly (P < 0.01) higher breast meat drip and cook losses, Allo-Kramer shear values and collagen content. In comparison with FG and SG, MG exhibited a higher breast meat pH (5.86% v. 5.79% and 5.78%, respectively; P < 0.01) and a lower lightness (54.88% v. 57.81% and 56.98%, respectively; P < 0.05). Genotype dramatically affected the lipid content as well as the fatty acid composition of both breast and thigh meat. SG exhibited the lowest content of lipid, both in breast and in thigh meat, the lowest proportions of monounsaturated fatty acids (MUFA) and the highest proportions of polyunsaturated fatty acids (PUFA). The total n-3 PUFA of SG breast meat was double that of FG meat and intermediate with respect to MG birds (8.07% v. 4.07% v. 5.14% total fatty acids; P < 0.01). The fatty acid composition of thigh meat is similar to that of breast meat, but the differences among genotypes are less pronounced. Total saturated fatty acids were not affected by the genotype. In conclusion, meat functional properties of FG and MG strains appeared much more attractive both for industry and consumer (lower drip and cook losses and higher tenderness), whereas from a nutritional point of view, meat from SG appeared healthier (less fat and higher content of n-3 PUFA) and thus might better fit with the consumer's expectations of organic products.     

Production of an active recombinant thrombomodulin derivative in transgenic tobacco plants and suspension cells

Thrombomodulin is a membrane-bound protein that plays an active role in the blood coagulation system by binding thrombin and initiating the protein C anticoagulant pathway. Solulin™ is a recombinant soluble derivative of human thrombomodulin. It is used for the treatment of thrombotic disorders. To evaluate the production of this pharmaceutical protein in plants, expression vectors were generated using four different N-terminal signal peptides. Immunoblot analysis of transiently transformed tobacco leaves showed that intact Solulin™ could be detected using three of these signal peptides. Furthermore transgenic tobacco plants and BY2 cells producing Solulin™ were generated. Immunoblot experiments showed that Solulin™ accumulated to maximum levels of 115 and 27 μg g⁻¹ plant material in tobacco plants and BY2 cells, respectively. Activity tests performed on the culture supernatant of transformed BY2 cells showed that the secreted Solulin™ was functional. In contrast, thrombomodulin activity was not detected in total soluble protein extracts from BY2 cells, probably due to inhibitory effects of substances in the cell extract. N-terminal sequencing was carried out on partially purified Solulin™ from the BY2 culture supernatant. The sequence was identical to that of Solulin™ produced in Chinese hamster ovary cells, confirming correct processing of the N-terminal signal peptide. We have demonstrated that plants and plant cell cultures can be used as alternative systems for the production of an active recombinant thrombomodulin derivative.     

Responses of growth and phlorotannins in <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> to nutrient enrichment and herbivory

Discharge from anthropogenic sources may modify both macroalgal growth patterns and resource allocation to carbon based secondary compounds, thereby affecting their susceptibility for herbivory. We tested the effect of eutrophication in terms of nutrient enhancement on growth and phlorotannin concentration of Fucus vesiculosus by conducting manipulative experiments in the field and mesocosms. In the field experiment we utilised fish farms as nutrient sources and in the mesocosm-experiment we manipulated ambient nutrient levels and occurrence of the herbivorous isopod Idotea baltica. Vicinity of a fish farm affected neither growth nor the phlorotannin concentration of Fucus but increased the amount of epiphytes growing on Fucus. Other organisms such as epiphytic filamentous algae and periphyton, which are more capable of quickly utilizing excess nutrients, may restrain the direct effects of nutrient enhancement on Fucus. In a manipulative mesocosm experiment, neither nutrient enrichment nor occurrence of herbivores affected phlorotannin concentration implying lack of induced defences, at least in terms of increasing phlorotannin concentration. Feeding of thallus decreased the growth rate of algae, but the number of reproductive organs, receptacles, was not affected by herbivory. The negative effect of herbivory on the amount of apical tips tended to be stronger under nutrient enriched conditions. We conclude that eutrophication processes, in terms of nutrient enrichment, does not have strong direct effect on growth or phlorotannin production of F. vesiculosus. However, there may be important indirect consequences. First, herbivory may be targeted more to apical parts of the thallus under eutrophicated conditions. Second, the result that Fucus growing close to nutrient sources were smaller than those in control areas may reflect differences in mortality schedules of algae between eutrophicated and control areas.     

Environmental Impacts of Wild Caught Cod and Farmed Salmon - A Comparison with Chicken (7 pp)

Goal, Scope and Background The objective of this study was to assess environmental impacts of Norwegian cod fishing and salmon farming and compare these with chicken farming in order to find reference levels for environmental performance and identify problem areas and potentials for improvements. Methods A Life Cycle Screening following the production of 0.2 kg fillets as a functional unit through the respective food chains is performed for all 3 products. The analysis is partly quantitative and qualitative focusing on energy use, antifouling and land use impacts. Case studies are performed to investigate potentials for improvements within the fisheries and aquaculture industry. Results and Conclusions It can be concluded that the fishing phase for the cod and the feeding phase for both salmon and chicken dominate for all environmental impacts considered. Chicken is most energy effective followed by salmon and cod, which are almost on the same level. The area of sea floor affected by bottom trawling is around 100 times larger than the land area needed to produce the chicken feed for production of the 0.2 kg fillet. - The case studies show potentials for improvement of environmental performance, both for salmon farming and cod fishing, especially when it comes to energy use. The environmental impacts on the sea floor imposed by bottom trawling are not fully explored, but based on the precautionary principle a reasonable conclusion is that bottom trawls with less impact on the sea floor should be developed. Recommendation and Perspective LCA methods have initially been developed for land based industrial applications. More effort should be given to adapt these to fishing applications in order to obtain more accurate assessment of environmental impacts from seafood products. It is recommended to put more emphasis in finding improved indicators for impacts imposed by over-fishing, fuel emission from combustion at sea, use of antifouling and seafloor ecosystem disturbance.     

Risky Business: Temporal and Spatial Variation in Preindustrial Dryland Agriculture

Traditional dryland agriculture in the Pacific island was often labor-intensive and risky, yet settlement and farming in dry areas played an important role in the development of Polynesian societies. We investigate how temporal and spatial climatic fluctuations shape variation in agricultural production across dryland landscapes. We use a model that couples plant growth, climate, and soil organic matter dynamics, together with data from Kohala, Hawai'i, to understand how temperature, rainfall, nitrogen availability, and cropping activity interact to determine yield dynamics through time and space. Due to these interactions, the statistical characterization of rainfall alone is a poor characterization of agricultural yield. Using a simple linear model of human population dynamics, we show that the observed yield variation can affect long-term population growth substantially. Our approach to analyzing spatial and temporal fluctuations in food supply, and to interpreting the population consequences of these fluctuations, provides a quantitative evaluation of agricultural risk and human carrying capacity in dry regions.     

Body size changes among otters, Lutra lutra, in Norway: the possible effects of food availability and global warming

Using museum data of adult specimens whose sex, age, and locality are known, we studied temporal and geographical body size trends among the otter, Lutra lutra, in Norway. We found that body size of the otters increased during the last quarter of the twentieth century, and suggest that this trend is related to increased food availability from fish farming and possibly also to energy saving due to elevated sea temperatures. Birth year and death year explained 38.8 and 43.5%, respectively, of the variation in body size. Body size of otters was positively related to latitude, thus conforming to Bergmann’s rule.     

Synthesis of enzymatically active human alpha-L-iduronidase in Arabidopsis cgl (complex glycan-deficient) seeds

As an initial step to develop plants as systems to produce enzymes for the treatment of lysosomal storage disorders, Arabidopsis thaliana wild-type (Col-0) plants were transformed with a construct to express human alpha-l-iduronidase (IDUA; EC 3.2.1.76) in seeds using the promoter and other regulatory sequences of the Phaseolus vulgaris arcelin 5-I gene. IDUA protein was easily detected on Western blots of extracts from the T(2) seeds, and extracts contained IDUA activity as high as 2.9 nmol 4-methylumbelliferone (4 MU)/min/mg total soluble protein (TSP), corresponding to approximately 0.06 microg IDUA/mg TSP. The purified protein reacted with an antibody specific for xylose-containing plant complex glycans, indicating its transit through the Golgi complex. In an attempt to avoid maturation of the N-linked glycans of IDUA, the same IDUA transgene was introduced into the Arabidopsis cgl background, which is deficient in the activity of N-acetylglucosaminyl transferase I (EC 2.4.1.101), the first enzyme in the pathway of complex glycan biosynthesis. IDUA activity and protein levels were significantly higher in transgenic cgl vs. wild-type seeds (e.g. maximum levels were 820 nmol 4 MU/min/mg TSP, or 18 microg IDUA/mg TSP). Affinity-purified IDUA derived from cgl mutant seeds showed a markedly reduced reaction with the antibody specific for plant complex glycans, despite transit of the protein to the apoplast. Furthermore, gel mobility changes indicated that a greater proportion of its N-linked glycans were susceptible to digestion by Streptomyces endoglycosidase H, as compared to IDUA derived from seeds of wild-type Arabidopsis plants. The combined results indicate that IDUA produced in cgl mutant seeds contains glycans primarily in the high-mannose form. This work clearly supports the viability of using plants for the production of human therapeutics with high-mannose glycans.     

Research advances in plant-made flavivirus antigens

Outbreaks of flaviviruses such as dengue (DV), yellow fever (YFV), Japanese encephalitis (JEV), tick-borne encephalitis (TBEV) and West Nile (WNV) affect numerous countries around the world. The fast spread of these viruses is the result of increases in the human population, rapid urbanisation and globalisation. While vector control is an important preventive measure against vector-borne diseases, it has failed to prevent the spread of these diseases, particularly in developing countries where the implementation of control measures is intermittent. As antiviral drugs against flaviviruses are not yet available, vaccination remains the most important tool for prevention. Although human vaccines for YFV, TBEV and JEV are available, on-going vaccination efforts are insufficient to prevent infection. No vaccines against DENV and WNV are available. Research advances have provided important tools for flavivirus vaccine development, such as the use of plants as a recombinant antigen production platform. This review summarises the research efforts in this area and highlights why a plant system is considered a necessary alternative production platform for high-tech subunit vaccines.