A comparison of rapid bovine spongiform encephalopathy testing methods on autolyzed bovine brain tissue.

In 1999, the European Union (EU) approved 3 rapid methods for the testing of bovine brain samples for the presence of bovine spongiform encephalopathy (BSE). The evaluation that led to the approval did not include an analysis of autolyzed material. Member states of the EU have active surveillance programs for BSE, which target fallen stock as well as other categories of cattle. Autolysis is a common feature of fallen stock samples because there can be a considerable delay between death and collection of samples. Therefore, it is important to know whether these tests perform optimally on autolyzed samples. The Veterinary Laboratories Agency (VLA) selected 250 positive fallen stock samples. These had been detected during routine testing using the Prionics-Check Western blot and confirmed as BSE cases by immunohistochemistry or electron microscopy. Samples were graded according to the degree of autolysis and then tested by the 3 methods: Prionics-Check Western blot, Platelia test, and Enfer test. All 3 methods correctly classified the samples as positive BSE cases, therefore alleviating doubt about their ability to do so. Subsequent EU validation exercises, such as those conducted in 2002--2003, have included the testing of autolyzed material. It is important that all new methods be evaluated on autolyzed tissue before approval for official use.     

Winter × spring wheat hybridization - a promising avenue for yield enhancement

Introgression of the winter gene pool into spring wheat is being considered as one of the strategies to break through the yield plateau. However, little information is available on the combining ability of these two important but distinct groups of wheats in Indian conditions. Therefore, the present study was undertaken to determine the combining ability and gene action of yield and yield attributes in winter × spring wheat crosses. Seventy F₁ progenies developed by 14 winter and five spring wheat lines using a line × tester design were evaluated, along with their parents, for yield and yield attributes in a randomized complete block design under field conditions. The mean squares for all the characters studied showed highly significant differences. The mean squares due to female × male interactions were significant for all the characters studied except for grains per ear and grain weight per ear. Additive genetic effects were found to play a key role in controlling the expression of days to heading, plant height and spikelets per ear.‘MV 19’ and ‘Stepniak’/‘Karvuna’ among winter and ‘PBW 65’ among spring wheats were good general combiners for most of the yield attributes studied. The estimates for specific combining ability effects suggested that, although general combining ability (GCA) effects of most winter wheats are either average or poor, their combination can give desirable genotypes with spring wheat parents possessing a high GCA.     

Postindustrial melanism in the peppered moth

New data show the geographical pattern of frequency of the melanic morph carbonaria of the peppered moth, Biston betularia, in 1983-84. These frequencies are compared with data from 1952 to 1970. After 20 years of smoke control, the area of high melanic frequency has contracted to the northeast. The change indicates a disadvantage to carbonaria of about 12 percent compared with 20 years ago. Computer simulations, which do not include the assumption of heterozygote advantage, provide a good match to the surface for the period 1952 to 1970, and also the 1983-84 surface. Experiments on visual predation have been criticized as giving unrepresentative estimates of selection but they permit satisfactory simulations to be made.     

Requirement for DARPP-32 in progesterone-facilitated sexual receptivity in female rats and mice

DARPP-32, a dopamine- and adenosine 3',5'-monophosphate (cAMP)-regulated phosphoprotein (32 kilodaltons in size), is an obligate intermediate in progesterone (P)-facilitated sexual receptivity in female rats and mice. The facilitative effect of P on sexual receptivity in female rats was blocked by antisense oligonucleotides to DARPP-32. Homozygous mice carrying a null mutation for the DARPP-32 gene exhibited minimal levels of P-facilitated sexual receptivity when compared to their wild-type littermates. P significantly increased hypothalamic cAMP levels and cAMP-dependent protein kinase activity. These increases were not inhibited by a D1 subclass dopamine receptor antagonist. P also enhanced phosphorylation of DARPP-32 on threonine 34 in the hypothalamus of mice. DARPP-32 activation is thus an obligatory step in progestin receptor regulation of sexual receptivity in rats and mice.     

Comparative genome and proteome analysis of Anopheles gambiae and Drosophila melanogaster

Comparison of the genomes and proteomes of the two diptera Anopheles gambiae and Drosophila melanogaster, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small "microsyntenic" clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected.     

Cross-species identification of Mendel's I locus

A key gene involved in plant senescence, mutations of which partially disable chlorophyll catabolism and confer stay-green leaf and cotyledon phenotypes, has been identified in Pisum sativum, Arabidopsis thaliana, and Festuca pratensis by using classical and molecular genetics and comparative genomics. A stay-green locus in F. pratensis is syntenically equivalent to a similar stay-green locus on rice chromosome 9. Functional testing in Arabidopsis of a homolog of the rice candidate gene revealed (i) senescence-associated gene expression and (ii) a stay-green phenotype after RNA interference silencing. Genetic mapping in pea demonstrated cosegregation with the yellow/green cotyledon polymorphism (I/i) first reported by Gregor Mendel in 1866.     

Genetic relationships and hybrid vigour in olive (Olea europaea L.) by microsatellites

The olive (Olea europaea) is one of the most important oleaginous crops of the Mediterranean basin. Increased demand for olive oil creates a need for new olive varieties to help meet the requirements of the global market. However, olive breeding has been handicapped by such varied challenges as a prolonged juvenile period, agrotechnical problems and insufficient genetic knowledge. The use of DNA markers has the potential to overcome these problems and increase the effectiveness of classical breeding programmes. In this study, co‐dominant polymorphic simple sequence repeats (SSRs) were used as markers to analyse the genetic relationships between several local and other ‘non‐native’ olive cultivars. Cluster analysis revealed four major groups among the 15 cultivars examined in this study. Table and oil cultivars were clustered in different groups. However, the clusters did not differentiate between cultivars of different geographical origins. In addition, we used the data gathered to analyse genetic relationships to evaluate the effects of heterosis in agricultural traits. Genetic distances between cultivars were determined based on the SSR genotype data and were used for evaluating the possible effects of heterosis in various F₁ populations. Interestingly, phenotypic data of F₁ progenies from crosses between different cultivars indicated the potential effects of heterosis as expressed in several traits. Genetic distance between parents was significantly correlated to F₁ performance for three traits: percentage of dry fruit weight, oil content and commercial oil production. Thus, crosses between olive cultivars exhibiting relatively extensive genetic distances one from the other are expected to result in better progeny performance in future Olea breeding programmes. Our study linked assessment of biodiversity of commercial olive cultivars with the application of this information in olive breeding programmes for selection of specific parents to generate superior new cultivars.