Pollination ecology of Arum italicum (Araceae)

The pollination ecology of Arum italicum was studied in south-western France. This plant attracts olfactory dung-breeding flies through deceit. These insects are principally represented by Diptera, all belonging to saprophyte families. The volatilization of the odouriferous compounds, responsible for their attraction, is achieved through the production of heat by the appendix. The insects are trapped for 24 h in order to participate in both sexual phases of the protogynous inflorescence. The male flowers produce three heat events during flowering. These peaks of heat seem to be involved in the spathe movements, since they occur during the opening of the inflorescence and the liberation of the insects. The last male heat event may be linked with the liberation of pollen and its dispersion by stimulating trapped flies. According to their frequency and pollen-load, two Psychoda species appear to be the most efficient pollinators ( P. crassipenis and P. pusilla ). Nevertheless, each of the other attracted species could play a significant role under different spatio-temporal conditions. Experiments on self-pollination have shown that obligate cross-pollination is necessary for A. italicum to set seeds. Moreover, hand- and natural-pollinated plants showed similarly high abortion frequencies suggesting that seed set may be more constrained by resources rather than by pollination limitation.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 205–214.     

How did an annual plant react to Pleistocene glaciations? Postglacial history of Rhinanthus angustifolius in Europe

The impact of climate fluctuations during the Pleistocene on the geographic structure of genetic variation in plant populations is well documented, but there is a lack of studies of annual species at the European scale. The present study aimed to infer the history of the widespread European annual Rhinanthus angustifolius C. C. Gmelin (Orobanchaceae). We explored variation in chloroplast DNA (cpDNA) sequences and amplified fragment length polymorphism (AFLP) in twenty-nine populations covering the entire distribution area of the species. Five AFLP groups were identified, suggesting at least two glacial refugial areas: one area in southwestern Europe and one large eastern area in the Balkan/Caucasus. Recolonization of previously glaciated areas mainly took place from the east of Europe. Despite the difference in life-history traits, the patterns found for the annual R. angustifolius show similarities with those of perennial species in terms of genetic diversity and geographic organization of genetic variation. Although organelle markers have typically been preferred in phylogeographic studies, the cpDNA variation in R. angustifolius did not show any clear geographic structure. The absence of geographic structure in the cpDNA variation may reflect persistence of ancestral polymorphisms or hybridization and introgression with closely-related species.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 1–13.     

Synthesis of Retinal Gangliosides During Chick Embryonic Development

Abstract: Embryonic retina cells incorporated radioactivity from D-[6-³H]glucosamine into gangliosides in vitro. The incorporation was higher in retinas from younger embryos. The pattern of labeling of individual gangliosides of the retina changed gradually from a predominant labeling of gangliosides running chromatographically as GD₃ (nomenclature of Svennerholm) and GM₃ in retinas from 8-day-old embryos to a predominant labeling of those running as GD_Ia and GT, in retinas from 13–18-day-old embryos and newly hatched chicks. The shift in the pattern of labeling correlated with a temporary increase of about sixfold of the activity of UDP-N-acetyl-galactosamine:GM₃ N-acetylgalactosaminyltransferase occurring between days 8 and 14 of embryonic development and with a regular increase of the activity of the UDP-galactose:GM₂ galactosyltransferase occurring from day 8 until hatching. The activities of the CMP-NeuAc:lactosylceramide-, CMP-NeuAc:GM_3-, and CMP-NeuAc:GM₁-sialosyltransferases in the retinas of newly hatched chicks were 40, 20, and 40%(in comparison with the corresponding activities determined in retinas of the 8-day-old embryo.     

In vivo incorporation of [14C]tyrosine into the C-terminal position of the α subunit of tubulin

In vitro incorporation of [¹⁴C]tyrosine into the C-terminal position of the α subunit of tubulin was not affected by 4 mm cycloheximide. This inhibitor of protein synthesis was used for in vivo experiments. The in vivo incorporation of [¹⁴C]tyrosine into soluble brain protein of cycloheximide-treated rats was 10% of that of untreated rats. Treatment with vinblastine sulfate of the soluble brain protein showed that the incorporation of [¹⁴C]tyrosine into tubulin was higher in cycloheximide-treated than in untreated rats with respect to the incorporation into the total soluble protein. In the case of cycloheximide-treated rats, about 60% of the radioactivity incorporated into protein was released by the action of carboxypeptidase A, whereas 10% was liberated from the protein of untreated rats. The radioactive compound released by the action of carboxypeptidase A was identified as [¹⁴C]tyrosine. The α and β subunits of tubulin from animals that received [¹⁴C]tyrosine were separated by polyacrylamide gel electrophoresis. The radiosactivity ratio of $\text{α}\text{β}$ subunits of tubulin from cycloheximide-treated rats was threefold higher than that of untreated rats. When a mixture of [¹⁴C]amino acids was injected, the radioactivity ratio of $\text{α}\text{β}$ subunits of tubulin was similar for cycloheximide-treated and untreated rats. The results reported are consistent with the assumption that the α subunit of tubulin can be tyrosinated in vivo.     

The biosynthesis of gangliosides. The incorporation of galactose, N-acetylgalactosamine and N-acetylneuraminic acid into endogenous acceptors of subcellular particles from rat brain in vitro

Gangliosides bound to subcellular particles from rat brain were labelled by incubation of the particles (i) with CMP-N[(3)H]-acetylneuraminic acid and (ii) simultaneously, with CMP-N[(3)H]-acetylneuraminic acid and UDP-N-acetyl-[(14)C(1)]galactosamine or with CMP-N[(3)H]-acetylneuraminic acid and UDP-[U-(14)C]-galactose. Analysis of the labelled gangliosides showed that in (i), (a) the labelling was mostly in the neuraminidase-labile sialyl groups, (b) rigid relationships exist between the enzymes and the sialyl acceptors; the enzymes are not free to interact with all the specific substrates present in the preparation and (c) the precursor of the trisialoganglioside was the major disialoganglioside with a sialyl 2-->8 sialyl group. In (ii), (a) precursor-product relationships between the main pools of each ganglioside apparently do not exist, (b) for the labelling of Tay-Sachs ganglioside the amount formed from hematoside was at least 2.5 times that from aminoglycolipid and (c) the major monosialoganglioside was the precursor for the major disialoganglioside with a sialyl 2-->8 sialyl group.