Limiting nutrients: an old problem with new solutions?

Iron and phosphorus are essential minerals for both humans and plants. Advances in our understanding of the molecular mechanisms involved in the mobilization, transport and storage of these minerals now allow us to engineer plants to improve the yield and mineral nutrition of crops. Strategies range from increasing the expression of endogenous genes, such as that encoding the iron storage protein ferritin, to expressing a phytase gene from the fungus Aspergillus in Arabidopsis, thereby allowing the plants to obtain a previously unusable pool of phosphorus.     

Hammerhead redux: Does the new structure fit the old biochemical data?

The cleavage rates of 78 hammerhead ribozymes containing structurally conservative chemical modifications were collected from the literature and compared to the recently determined crystal structure of the Schistosoma mansoni hammerhead. With only a few exceptions, the biochemical data were consistent with the structure, indicating that the new structure closely resembles the transition state of the reaction. Since all the biochemical data were collected on minimal hammerheads that have a very different structure, the minimal hammerhead must be dynamic and occasionally adopt the quite different extended structure in order to cleave.     

Environmental genomics, the big picture?

The enormous sequencing capabilities of our times might be reaching the point of overflowing the possibilities to analyse data and allow for a feedback on where to focus the available resources. We have now a foreseeable future in which most bacterial species will have an annotated genome. However, we know also that most prokaryotic diversity would not be included there. On the one hand, there is the problem of many groups not being easily amenable to culture and hence not represented in culture-centred microbial taxonomy. On the other hand, the gene pools present in one species can be orders of magnitude larger than the genome of one strain (selected for genome sequencing). Contrasting with eukaryotic genomes, the repertoire of genes present in one prokaryotic cell genome does not correlate stringently with its taxonomic identity. Hence gene catalogues from one environment might provide more meaningful information than the classical species catalogues. Metagenomics or microbial environmental genomics provide a different tool that gravitates around the habitat rather than the species. Such a tool could be just the right way to complement "organismal genomics". Its potential to advance our understanding of microbial ecology and prokaryotic diversity and evolution is discussed.     

Do big females have big pelves?

Previous studies have shown that maternal stature is a correlate of both pelvic size and reproductive efficiency. This study addresses the issue of body size and obstetric advantage. The relationship between pelvic size and three nonpelvic measures of body size is determined for females and males. The skeletal sample consists of blacks, whites, and Native Americans. The variables include 28 measures of the pelvis, length and head diameter of the femur, and clavicular length. The coefficient of multiple determination (CMD) is computed for each pelvic measure using multiple regression, with the three nonpelvic measures serving as the independent variables. Partial correlation coefficients are also calculated between each pelvic and nonpelvic variable, while controlling for the other two nonpelvic variables. The results show that all CMDs in females and all but one CMD in males are "low," i.e., below 33%. The sexes are nonsignificantly different in their CMDs for 22 of the 28 pelvic variables; of the six variables that are significantly different, five are of the midplane. The sexes are also broadly comparable in their partial correlations. The results are explained as follows. First, the concordance between the sexes in the relationship between pelvic size and nonpelvic measures of body size is due to their genetic similarity for homologous structures. Second, as pelvic size is at the minimum at the midplane, the sexual differences in CMDs are the result of selection with respect to obstetrics. Third, four explanations for the low CMDs are discussed: 1) lack of populationally or racially specific analysis; 2) nonlinear relationship between pelvic size and nonpelvic measures of body size; 3) combination of negative allometric selection between newborn body weight and maternal stature and weight with positive selection for maternal pelvic size; and 4) hormonally induced increase in pelvic capacity during parturition.     

Resistance to plant viruses: old issue,news answers?

Viruses represent significant threats to modern agriculture and their biological control remains a challenge in the twenty-first century. Recent progress has been made in our understanding of natural and engineered virus resistance, the two major strategies used for crop protection. The molecular mechanisms underlying the roles of both dominant and recessive resistance genes have been elucidated, promoting the development of possible new antiviral strategies. Engineering resistance in plants, in particular RNA-mediated protection, is also becoming increasingly important and is likely to play a key role in the future.     

Extreme longevity in trees: live slow, die old?

We have examined the extreme longevity displayed by trees in relation to a theory mainly developed in animals, namely, the controversial rate of living (ROL) theory of aging which proposes that longevity is negatively correlated to metabolic rate. Plant metabolism implies respiration and photosynthesis; both are susceptible to negatively impact longevity. The relationship between longevity and metabolism was studied in leaves and stems of several species with the aim of challenging the ROL theory in trees. Leaf and stem life spans were found to be highly correlated to metabolism (R(2) = 0.97), and stems displayed a much lower metabolism than leaves. Analysis of covariance (ANCOVA), with metabolism as the covariate, revealed no difference between mean leaf and stem life spans, which would appear to conform to the expectations of the ROL theory. Consequently, the extremely high longevity of trees may be explained by the lower metabolism displayed by the stems. These results clearly reflect different energy allocation and energy expenditure rate strategies between leaves and stems, which may result in different senescence rates (and life spans) in these organs. They also suggest that, in contrast to animals, the ROL theory of aging may apply to woody plants at the organ level, thereby opening a promising new line of research to guide future studies on plant senescence.     

European genomics: think big or small?

With the first draft of the human genome completed, Michael Gross looks at some of the plans to study a variety of European populations to exploit the new information.     

Malaria: new vaccines for old?

Detailed analyses of the 5500 genes revealed by the complete Plasmodium genome sequence are yielding new candidate parasite antigens and strategies that may contribute to a successful vaccine against malaria in the coming decade.     

How many, how old, how soon?

This article highlights the population projections for the UK to 2066 and their health implications. The changes in the demographic age structure of human populations have dual implications. Although they represent accomplishments in social and health development considering the fact that more individuals are able to live until old age, these changes also bring new demands that affect all aspects of society, including employment, taxation, pension, education, and health. Age specific population projections presented were obtained from the Office for National Statistics. It is projected that the total number of people aged 60 years and older will rise from 12 million in 2001 to 18.6 million in 2031 and the number of individuals suffering with chronic diseases and disabilities will see a three-fold increase. Although these projections rely on assumptions and are subject to some changes, it is made clear that the proportion of the population aged 65 and above will continue to increase substantially over the next decades. These population trends will have a large impact on the health and health care needs of the population. Thus, there is a need to develop and plan institutions and policies that address the demands of the aging population. Understanding and identification of the causes and prevention of conditions that could result to serious disabilities must be a high priority.     

Fluctuating asymmetry in an insect host: a big role for big parasites?

Parasites are expected to be associated with host developmental instability because developmentally unstable hosts may be more susceptible to, or more frequently exposed to, parasitic infections compared with developmentally stable ones, or because parasites may directly disrupt host development. In this study, we analysed the relationship between developmental stability in the weta Pleioplectron simplex (Orthoptera) and infections by hairworm and mermithid parasites. These parasites have a long development in their host and the size of adult worms exceeds the length of the host by a considerable amount (15–20 cm). For one character (femora) we found that fluctuating asymmetry was significantly higher in parasitized individuals compared with unparasitized ones, in each of two samples collected in different years. Because no relationship was observed between the level of fluctuating asymmetry and the parasite size or number, however, infection by hairworm and mermithid parasites could be more a consequence of developmental instability than a cause. For other characters (tibia, external and internal spines of femora), the level of fluctuating asymmetry between parasitized and unparasitized individuals was not significantly different. Our results are discussed in relation to ecological constraints met by hairworm and mermithid parasites to complete their life cycle.     

Sheep farming business in Uşak city of Turkey: Economic structure,problems and solutions

The current study was conducted to reveal the current states, structural features and primary problems of the sheep raising businesses in the city of U?ak. The study group of the current study is comprised of 429 sheep raising businesses selected through stratified sampling (provinces) and a questionnaire consisted of 112 items was administered to these businesses. Through the items in the questionnaire, data were collected about the general features of the businesses and their owners, the state of grazing lands, mating of sheep, birth, milking, clipping, health protection, marketing of animals and the states of tools and equipments in the businesses.The findings of the study have revealed that 82.2% of the owners of the sheep raising businesses are elementary school graduates, their average time of being involved in the activity of sheep raising is 9.8?years, 90% of their shepherds are from the family members, 23.5% of them practice additional feeding before mating and the most preferred method for mating is free insemination with 89%.Of the owners of the businesses, 81.1% learned sheep raising from their elders; for 54% of them sheep raising is the sole source of income and 25.6% of them are engaged in sheep raising to support their families. The main problems of the sheep raisers were found to be the high cost of feed, the low prices paid for their products, inadequate and poor quality grazing lands and animal diseases. In order to make sheep raising more attractive, the prices of the products should be increased, grazing lands should be improved, the genetic structure of the herd should be enhanced, the amount of land area where feed crops are cultivated should be extended and suitable credit conditions should be provided. On the other hand, they need to be informed about sheep mating, lamb growing, stock, milking hygiene, general sheep feeding practices and marketing.