THE COMPARISON OF QUANTITATIVE GENETIC PARAMETERS BETWEEN POPULATIONS

A statistical method for comparing matrices of genetic variation and covariation between groups (e.g., species, populations, a single population grown in distinct environments) is proposed. This maximum-likelihood method provides a test of the overall null hypothesis that two covariance component matrices are identical. Moreover, when the overall null hypothesis is rejected, the method provides a framework for isolating the particular components that differ significantly between the groups. Simulation studies reveal that discouragingly large experiments are necessary to obtain acceptable power for comparing genetic covariance component matrices. For example, even in cases of a single trait measured on 900 individuals in a nested design of 100 sires and three dams per sire in each population, the power was only about 0.5 when additive genetic variance differed by a factor of 2.5. Nevertheless, this flexible method makes valid comparison of covariance component matrices possible.     

Two different begomovirus species are associated with yellow vein mosaic disease of okra in Sri Lanka

Molecular Biology Reports - Yellow vein mosaic disease is the major biotic constraint of okra cultivation in Sri Lanka. Identification and detailed molecular characterization of associated pathogen...     

A rapid ceramide synthase activity using NBD-sphinganine and solid phase extraction

Ceramides are synthesized by six mammalian ceramide synthases (CerSs), each of which uses fatty acyl-CoAs of different chain lengths for N-acylation of the sphingoid long-chain base. We now describe a rapid and reliable CerS assay that uses a fluorescent N-[6-[(7-nitrobenzo-2-oxa-1,3-diazol-4-yl) (NBD) sphinganine substrate followed by separation of the NBD-lipid substrate and products using solid phase extraction (SPE) C18 chromatography. SPE chromatography is a quick and reliable alternative to TLC, and moreover, there is no degradation of either NBD-sphinganine or NBD-ceramide. We have optimized the assay for use with minimal amounts of protein in a minimal volume. This assay will prove useful for the analysis of CerS activity, which is of particular importance in light of the growing involvement of CerS in cell regulation and in the pathology of human diseases.     

Evolution of the Monotremes: Phylogenetic Relationship to Marsupials and Eutherians, and Estimation of Divergence Dates Based on α-Lactalbumin Amino Acid Sequences

The amino acid sequences of the -lactalbumins of the echidna, Tachyglossus aculeatus, and the platypus, Ornithorhynchus anatinus, were compared with each other and with those of 13 eutherian and 3 marsupial species. Phylogenetic parsimony analyses, in which selected mammalian lysozymes were used as outgroups, yielded trees whose consensus indicated that the two monotremes are sister taxa to marsupials and eutherians and that the latter two clades are each other's closest relatives. The data do not support the notion of a Marsupionta (monotreme–marsupial) clade. Pairwise comparison between the -lactalbumins yielded maximum-likelihood distances from which divergence dates were estimated on the basis of three calibration points. The distance data support the view that the echidna and platypus lineages diverged from their last common ancestor at least 50 to 57 Ma (million years ago) and that monotremes diverged from marsupials and eutherian mammals about 163 to 186 Ma.     

Relationship of the env genes and the endonuclease domain of the pol genes of simian foamy virus type 1 and human foamy virus.

We have molecularly cloned and sequenced a portion of the simian foamy virus type 1 (SFV-1); open reading frames representing the endonuclease domain of the polymerase (pol) and the envelope (env) genes were identified by comparison with the human foamy virus (HFV). Unlike the HFV genomic organization, the SFV-1 pol gene overlaps the env gene; thus, the open reading frames reported for HFV between pol and env is not present in SFV-1. Comparisons of predicted amino acid sequences of HFV and SFV-1 reveal that the endonuclease domains of the pol genes are about 84% related. The region predicted to encode the SFV-1 extracellular env domain is 569 codons; SFV-1 and HFV have 64% amino acid similarity in this env domain. The predicted hydrophobic transmembrane env proteins of both HFV and SFV-1 show about 73% similarity. A total of 16 potential glycosylation sites are found in SFV-1 env, and 15 are found in HFV; 11 are shared. SFV-1 has 25 cysteine residues, and HFV has 23 residues; all 23 cysteine residues of HFV are conserved in SFV-1. This sequence analysis reveals that the human and simian foamy viruses are highly related.     

Cortical microtubule arrays in the Arabidopsis seedling

Advances in live-cell imaging technology have provided an unprecedented look at the dynamic behaviors of the plant microtubule cytoskeleton. Recent studies revisit the classic question of how plants create cell shape through the patterned construction of the cell wall. Visualization of the cellulose synthase complex traveling in the plasma membrane has brought a watershed of new information about cellulose deposition. Observation of the cellulose synthase complex tracking precisely over the underlying cortical microtubules has provided clear evidence that the microtubule array pattern serves as a spatial template for cellulose microfibril extrusion. Understanding how the microtubules are organized into specific array patterns remains a challenge, though new ideas are arising from genetic and cell biological studies. Long-term time-lapse observations of the microtubule arrays in light-grown hypocotyl cells have revealed a striking process of microtubule patterning possibly linked to the creation of polylamellate cell walls.     

Characterization of a protein fraction containing cytochromes b and c1 from mitochondria of Leishmania tarentolae

A soluble red band fraction was obtained from Leishmania tarentolae cells by sucrose gradient sedimentation of a Triton X-100 lysate. Spectral analysis indicated that cytochrome b was present in the red band: the reduced minus oxidized difference spectra revealed absorption maxima at 562,527, and 431 nm at room temperature and 562, 530, and 422 nm at 77K. In addition, a 28-kDa protein was identified in this fraction which retained heme-associated peroxidase activity even after denaturation on SDS-polyacrylamide gels. The amino acid composition of this protein showed a strong similarity to cytochrome c1 of both bovine and yeast.