The intracellular distribution of adenylate kinase in the leaves of spinach,wheat and barley

Of the total adenylate-kinase activity in 10-d-old barley and wheat leaves, 40–50% is localised in the chloroplasts, while in mature spinach leaves 50–70% of the enzyme is chloroplastic. The extra-chloroplastic adenylate-kinase activity is associated with the mitochondria, very little, if any, is freely soluble in the cytoplasm. The adenylate pool of the cytoplasm could have access to adenylate-kinase activity in the intermitochondrial space because of the free permeation of adenylates across the outer mitochondrial membrane. Thus the adenylate pool of the cytoplasm could be subject to adenylate-kinase equilibrium. The mitochondrial adenylate kinase appeared to the localised exclusively in the intermembrane space.     

Influence of a naturally occurring competing enzymic activity on studies of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity.

An enzymic activity which competes with 3-hydroxy-3-methylglutaryl coenzyme A reductase for D-hydroxymethylglutaryl CoA has been found in isolated rat liver microsomes and in microsomal extracts. The presence of this activity in enzyme preparations causes a decrease in the rate of mevalonate formation leading to an underestimation of reductase activity and an overestimation of the apparent Km of the reductase. The product formed by this competing enzymic activity behaves similarly to, but not identically with, mevalonolactone when chromatographed on Bio-Rad AG 1-x8 formate, which is used in many reductase assay procedures to separate mevalonolactone from hydroxymethylglutaryl CoA. Removal of this competing enzymic activity from reductase preparations can be accomplished by gel filtration using Bio-Gel A 1.5m, by washing the microsomes or by incubating the microsomal extract at 37 degrees C. Using enzyme preparations free of this competing enzymic activity, the apparent Km values of the reductase for D-hydroxymethylglutaryl CoA and NADPH were found to be 1.3 and 26 micronM respectively.     

Hemoglobin binding by isolated polymeric proteins from human haptoglobin types 2-1 and 2-2. Some suggested polymer subunit compositions.

1. Some of the individual members of the polymeric series of proteins from human haptoglobin types 2-1 and 2-2 were isolated by gel electrophoresis. By reacting this purified material with less than an equivalent amount of hemoglobin and analyzing the result by electrophoresis, the number of haptoglobin-hemoglobin complexes could be clearly counted. For the haptoglobin 2-1 series, the number of complexes formed was n+1, where n is the serial order, in decreasing electrophoretic mobility, of the haptoglobin polymeric form used. For the haptoglobin 2-2 series, the number of complexes was n+2. 2. For the first three members of haptoglobin 2-1 series, the haptoglobin-hemoglobin composition of the complexes was estimated from scans of the unstained gels. The data indicated that this series consists of 2,3,4... alpha beta haptoglobin subunits, each of which can combine with an alpha beta subunit of hemoglobin.     

Molecular evidence for Gondwanan origins of multiple lineages within a diverse Australasian gecko radiation

Aim Gondwanan lineages are a prominent component of the Australian terrestrial biota. However, most squamate (lizard and snake) lineages in Australia appear to be derived from relatively recent dispersal from Asia (< 30 Ma) and in situ diversification, subsequent to the isolation of Australia from other Gondwanan landmasses. We test the hypothesis that the Australian radiation of diplodactyloid geckos (families Carphodactylidae, Diplodactylidae and Pygopodidae), in contrast to other endemic squamate groups, has a Gondwanan origin and comprises multiple lineages that originated before the separation of Australia from Antarctica. Location Australasia. Methods Bayesian (beast ) and penalized likelihood rate smoothing (PLRS) (r 8s ) molecular dating methods and two long nuclear DNA sequences (RAG‐1 and c‐mos) were used to estimate a timeframe for divergence events among 18 genera and 30 species of Australian diplodactyloids. Results At least five lineages of Australian diplodactyloid geckos are estimated to have originated > 34 Ma (pre‐Oligocene) and basal splits among the Australian diplodactyloids occurred c. 70 Ma. However, most extant generic and intergeneric diversity within diplodactyloid lineages appears to post‐date the late Oligocene (< 30 Ma). Main conclusions Basal divergences within the diplodactyloids significantly pre‐date the final break‐up of East Gondwana, indicating that the group is one of the most ancient extant endemic vertebrate radiations east of Wallace’s Line. At least five Australian lineages of diplodactyloid gecko are each as old or older than other well‐dated Australian squamate radiations (e.g. elapid snakes and agamids). The limbless Pygopodidae (morphologically the most aberrant living geckos) appears to have radiated before Australia was occupied by potential ecological analogues. However, in spite of the great age of the diplodactyloid radiation, most extant diversity appears to be of relatively recent origin, a pattern that is shared with other Australian squamate lineages.     

Contrasting consequences of climate change for migratory geese: Predation,density dependence and carryover effects offset benefits of high‐arctic warming

Climate change is most rapid in the Arctic, posing both benefits and challenges for migratory herbivores. However, population‐dynamic responses to climate change are generally difficult to predict, due to concurrent changes in other trophic levels. Migratory species are also exposed to contrasting climate trends and density regimes over the annual cycle. Thus, determining how climate change impacts their population dynamics requires an understanding of how weather directly or indirectly (through trophic interactions and carryover effects) affects reproduction and survival across migratory stages, while accounting for density dependence. Here, we analyse the overall implications of climate change for a local non‐hunted population of high‐arctic Svalbard barnacle geese, Branta leucopsis, using 28 years of individual‐based data. By identifying the main drivers of reproductive stages (egg production, hatching and fledging) and age‐specific survival rates, we quantify their impact on population growth. Recent climate change in Svalbard enhanced egg production and hatching success through positive effects of advanced spring onset (snow melt) and warmer summers (i.e. earlier vegetation green‐up) respectively. Contrastingly, there was a strong temporal decline in fledging probability due to increased local abundance of the Arctic fox, the main predator. While weather during the non‐breeding season influenced geese through a positive effect of temperature (UK wintering grounds) on adult survival and a positive carryover effect of rainfall (spring stopover site in Norway) on egg production, these covariates showed no temporal trends. However, density‐dependent effects occurred throughout the annual cycle, and the steadily increasing total flyway population size caused negative trends in overwinter survival and carryover effects on egg production. The combination of density‐dependent processes and direct and indirect climate change effects across life history stages appeared to stabilize local population size. Our study emphasizes the need for holistic approaches when studying population‐dynamic responses to global change in migratory species.     

Multiple chromosomal inversions contribute to adaptive divergence of a dune sunflower ecotype

Both models and case studies suggest that chromosomal inversions can facilitate adaptation and speciation in the presence of gene flow by suppressing recombination between locally adapted alleles. Until recently, however, it has been laborious and time‐consuming to identify and genotype inversions in natural populations. Here we apply RAD sequencing data and newly developed population genomic approaches to identify putative inversions that differentiate a sand dune ecotype of the prairie sunflower (Helianthus petiolaris) from populations found on the adjacent sand sheet. We detected seven large genomic regions that exhibit a different population structure than the rest of the genome and that vary in frequency between dune and nondune populations. These regions also show high linkage disequilibrium and high heterozygosity between, but not within, arrangements, consistent with the behaviour of large inversions, an inference subsequently validated in part by comparative genetic mapping. Genome–environment association analyses show that key environmental variables, including vegetation cover and soil nitrogen, are significantly associated with inversions. The inversions colocate with previously described “islands of differentiation,” and appear to play an important role in adaptive divergence and incipient speciation within H. petiolaris.     

Drivers of plant species composition of ecotonal vegetation in two fishpond management types

Wetlands Ecology and Management - Plants play an important role in fishpond littorals, but little is known about factors influencing their presence and growth patterns. We surveyed vegetation of...