Hormonally regulated programmed cell death in barley aleurone cells

Cell death was studied in barley (cv Himalaya) aleurone cells treated with abscisic acid and gibberellin. Aleurone protoplasts incubated in abscisic acid remained viable in culture for at least 3 weeks, but exposure to gibberellin initiated a series of events that resulted in death. Between 4 and 8 days after incubation in gibberellin, >70% of all protoplasts died. Death, which occurred after cells became highly vacuolated, was manifest by an abrupt loss of plasma membrane integrity followed by rapid shrinkage of the cell corpse. Hydrolysis of DNA began before death and occurred as protoplasts ceased production of alpha-amylase. DNA degradation did not result in the accumulation of discrete low molecular weight fragments. DNA degradation and cell death were prevented by LY83583, an inhibitor of gibberellin signaling in barley aleurone. We conclude that cell death in aleurone cells is hormonally regulated and is the final step of a developmental program that promotes successful seedling establishment.     

Expression of the alpha 1-proteinase inhibitor gene family during evolution of the genus Mus

alpha 1-Proteinase inhibitors (alpha 1-PIs) are members of the serpin superfamily of proteinase inhibitors, and are important in the maintenance of homeostasis in a wide variety of animal taxa. Previous studies have shown that in mice (genus Mus), evolution of alpha 1-PIs is characterized by gene amplification, region-specific concerted evolution, and rapid accumulation of amino acid substitutions. The latter occurs primarily in the reactive center, which is the region of the alpha 1-PI molecule that determines the inhibitor's specificity for target proteinases. The P1 residue within the reactive center, which is methionine in so-called orthodox alpha 1-PIs and an amino acid other than methionine in unorthodox alpha 1-PIs, is a primary determinant of inhibitor specificity. In the present study, we find that the expression of mRNAs encoding unorthodox alpha 1-PIs is polymorphic within Mus species, i.e., among individuals or inbred strains. This is in striking contrast to mRNAs that encode orthodox alpha 1-PIs, whose concentrations are relatively invariant. The intraspecies variations in mRNA expression represent polymorphisms in the structure of the alpha 1- PI gene family. The results, taken together with previously described aspects of alpha 1-PI evolution, indicate that the dissimilar levels of polymorphism exhibited by orthodox and unorthodox alpha 1-PIs, which likely have distinct physiological functions, may reflect different levels of selective constraint. The significance of this finding to the evolution of gene families is discussed.      

Changes in the skull morphology of the Arctic wolf, Canis lupus arctos, during the twentieth century

Measurements of a large series of skulls of the Arctic wolf, Canis lupus arctos . have shown that since 1930 there has been an overall reduction in the size of the skulls, together with widening of the cranium, shortening of the facial region, and reduction in size of the teeth. This suggests that hybridization and subsequent introgression occurred with huskies ( Canis familiaris ) during the 1930s, which is consistent with historical accounts. Since 1950 there has been a reversion in skull morphology to a more 'wolf-like' form, suggesting that hybridization is no longer occurring.
The skull of a wolf/dog hybrid is intermediate in size between the skulls of wolves and huskies but its shape is allometrically dissimilar. Skulls of wolves from the period 1930–50 are moi-e similar to the skull of this hybrid than in the other time periods.
The skull of a male canid from a carcass collected on Ellesmere Island and presented to the Natural History Museum. London, in 1986 was at first thought to be from a wolf/dog hybrid but analyses of the measurements show that it is more likely to be from an Arctic wolf with severe abnormalities to the jaws.     

Reconstructing mammalian phylogenies: a detailed comparison of the cytochrome B and cytochrome oxidase subunit I mitochondrial genes

The phylogeny and taxonomy of mammalian species were originally based upon shared or derived morphological characteristics. However, genetic analyses have more recently played an increasingly important role in confirming existing or establishing often radically different mammalian groupings and phylogenies. The two most commonly used genetic loci in species identification are the cytochrome oxidase I gene (COI) and the cytochrome b gene (cyt b). For the first time this study provides a detailed comparison of the effectiveness of these two loci in reconstructing the phylogeny of mammals at different levels of the taxonomic hierarchy in order to provide a basis for standardizing methodologies in the future. Interspecific and intraspecific variation is assessed and for the first time, to our knowledge, statistical confidence is applied to sequence comparisons. Comparison of the DNA sequences of 217 mammalian species reveals that cyt b more accurately reconstructs their phylogeny and known relationships between species based on other molecular and morphological analyses at Super Order, Order, Family and generic levels. Cyt b correctly assigned 95.85% of mammal species to Super Order, 94.31% to Order and 98.16% to Family compared to 78.34%, 93.36% and 96.93% respectively for COI. Cyt b also gives better resolution when separating species based on sequence data. Using a Kimura 2-parameter p-distance (x100) threshold of 1.5-2.5, cyt b gives a better resolution for separating species with a lower false positive rate and higher positive predictive value than those of COI.     

Remarkable ancient divergences amongst neglected lorisiform primates

Lorisiform primates (Primates: Strepsirrhini: Lorisiformes) represent almost 10% of the living primate species and are widely distributed in sub‐Saharan Africa and South/South‐East Asia; however, their taxonomy, evolutionary history, and biogeography are still poorly understood. In this study we report the largest molecular phylogeny in terms of the number of represented taxa. We sequenced the complete mitochondrial cytochrome b gene for 86 lorisiform specimens, including ～80% of all the species currently recognized. Our results support the monophyly of the Galagidae, but a common ancestry of the Lorisinae and Perodicticinae (family Lorisidae) was not recovered. These three lineages have early origins, with the Galagidae and the Lorisinae diverging in the Oligocene at about 30 Mya and the Perodicticinae emerging in the early Miocene. Our mitochondrial phylogeny agrees with recent studies based on nuclear data, and supports Euoticus as the oldest galagid lineage and the polyphyletic status of Galagoides. Moreover, we have elucidated phylogenetic relationships for several species never included before in a molecular phylogeny. The results obtained in this study suggest that lorisiform diversity remains substantially underestimated and that previously unnoticed cryptic diversity might be present within many lineages, thus urgently requiring a comprehensive taxonomic revision of this primate group. © 2015 The Linnean Society of London