Cyclic Expression of A Nuclear Protein In A Dinoflagellate

Nuclei of the dinoflagellate Crypthecodinium cohnii strain Whd were isolated and nuclear proteins were extracted in three fractions, corresponding to the increasing affinity of these proteins to genomic DNA. One fraction contained two major bands (48- and 46-kDa) and antibodies specific to this fraction revealed two major bands by Western blot on nuclear extracts, corresponding to the 46- and 48-kDa bands. The 48-kDa protein was detected in G1 phase but not in M phase cells. An expression cDNA library of C. cohnii was screened with these antibodies, and two different open reading frames were isolated. Dinoflagellate nuclear associated protein (Dinap1), one of these coding sequences, was produced in E. coli and appeared to correspond to the 48-kDa nuclear protein. No homologue of this sequence was found in the data bases, but two regions were identified, one including two putative zinc finger repeats, and one coding for two potential W/W domains. The second coding sequence showed a low similarity to non-specific sterol carrier proteins. Immunocytolocalization with specific polyclonal antibodies to recombinant Dinap1 showed that the nucleus was immunoreactive only during the G1 phase: the nucleoplasm was immunostained, while chromosome cores and nuclear envelopes were negative.     

Voice variance may signify ongoing divergence among black-legged kittiwake populations

Acoustic features are important for individual and species recognition. However, while dialectal variations in song characteristics have been described in many songbirds, geographical divergence in vocal features across populations has seldom been studied in birds that are not thought to have song-learning abilities. Here, we document marked differences in the vocal structure of calls of two populations of black-legged kittiwakes ( Rissa tridactyla ), a seabird whose call is considered as not being learned from other individuals. We found that calls vary both within and between populations. Within-population variation may convey individual identity, whereas the marked differences in frequency and temporal parameters observed between the two populations may reveal ongoing divergence among kittiwake populations. Moreover, we were unable to detect any sex signature in adult calls in a Pacific population (Middleton, Alaska), while these were detected in an Atlantic population (Hornøya, Norway), potentially affecting sexual behaviours. Despite the fact that these calls seemed to change over the reproductive season and across years, the individual signature remained fairly stable. Such vocal differences suggest that Pacific and Atlantic populations may be undergoing behavioural divergences that may reveal early stages of speciation, as is suggested by molecular data.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 289–297.     

Reversed sexual size dimorphism and parental care in the Red-footed Booby Sula sula

The 'division-of-labour' hypothesis predicts that males and females perform different roles in parental care and that natural selection acts differently on each sex so as to produce different body size optima suited to their particular roles. Reversed sexual size dimorphism in avian species (females larger than males) may therefore be an adaptive consequence of different roles of males and females in parental care. We investigated patterns of nest attendance, brooding, foraging and provisioning rate in a tropical seabird, the Red-footed Booby Sula sula , a species showing a reversed sexual size dimorphism. During incubation, females attended the nest more often than males, and spent more time brooding the small chick than did males during daytime. Males and females did not differ in the average duration of their foraging trips. During incubation, there was a positive relationship between nest attendance and the duration of foraging trips in males, but not in females. During the small-chick stage, for the same time spent at the nest, males spent significantly more time than females at sea. On average, females fed the chick more often than did males. In males, there was a significant and positive relationship between the probability of feeding the chick and the duration of the foraging trip, whereas in females, this probability was much less dependent on the duration of the foraging trip. Overall, female Red-footed Boobies achieved slightly, but significantly, more parental commitment than did males. However, these sexual differences in parental participation were small, suggesting a minimal division of labour in the Red-footed Booby. Our results suggest that the division of labour hypothesis is unlikely to explain fully the adult size dimorphism in Red-footed Boobies.     

Orthophosphate Relations of Root: NO-3 Effects on Orthophosphate Influx, Accumulation and Secretion into the Xylem

Lamaze, T., Sentenac, H. and Grignon, C. 1987. Orthophosphaterelations of root: NO^–₃effects on orthophosphate influx,accumulation and secretion into the xylem.—J. exp. Bot.38: 923–934. Orthophosphate (Pi) accumulation by barley (Hordeum vulgareL.) roots was specifically inhibited by NO^–₃ as comparedto Cl^– and SO₄^{2 –}, and Pi secretion into the xylemwas stimulated. The inhibition of Pi accumulation by NO^–₃was also observed in roots of intact photosynthesizing horsebean(Vicia faba L.), rice (Oryza sativa L.) and soybean (Glycinemax L.) plants. NO^–₃ effects on Pi transport by rootswere more thoroughly investigated with corn (Zea mays L.). Theywere due to intracellular NO^–₃. Pi secretion was stillstimulated by NO^–₃ after Pi withdrawal from the absorptionsolution. ³²Pi influx decreased during Pi accumulation, supportingthe hypothesis that this ion allosterically regulated its owntransport system by feedback control. This control was modulatedby other anions: the decrease was more pronounced in the presenceof nitrate. Chronologically, the depressive effect of NO^–₃on ³²Pi influx appeared after the inhibition of Pi accumulation.Furthermore, under conditions where Pi accumulation was notaffected by NO^–₃, ³²Pi influx and Pi secretion into thexylem became insensitive to the presence of nitrate. Our hypothesisis that the stimulative effect of NO^–₃ on Pi secretionand the depressive one on ³²Pi influx are the repercussionsof an increase in the Pi cytosolic concentration due to an NO^–₃-induced decrease in Pi uptake by the vacuoles. Key words: Root, orthophosphate fluxes, orthophosphate accumulation, nitrate, ionic interaction     

Carbon isotopic abundances in Mesozoic and Cenozoic fossil plants: Palaeoecological implications

Carbon isotopic abundances have been measured for more than one hundred samples of fossil plants ranging in age from middle Triassic to late Tertiary. Most of the plant fossils were identified at the specific or generic level and were selected as representing a variety of continental environments, including xeric and humid habitats. Material analysed included numerous fragments of flowers, seeds, fruits, leaves and wood, as well as a single amorphous lignite sample. The analyses performed for the plant fragments indicate relatively constant isotopic compositions during this time interval, with plant δ¹³C values ranging between -28 and -20%. These values are within the range for living terrestrial plants with C₃, photosynthesis, although values more positive than -23% are rare in C₃ plants and typically found in plants growing under environmental stress. Lower δ¹³C values might have been expected owing to the much higher CO₂, levels of the Cretaceous atmosphere that have been inferred from marine carbonates. No fossils with values indicating C₄, photosynthesis were discovered. Fossil plants from inferred mesic environments showed δ¹³C values ranging between -26.7 and -24.1%. Highest δ¹³C values in angiosperms (up to -20.1%) were measured for Late Cretaceous combretaceous flowers from Portugal. Some cheirolepidiaceous conifers from the Early Cretaceous also showed high δ¹³C values. Values measured for Pseudofrenelopsis varians and Glenrosa taxensis were -21.9%, and values of gymnosperm wood, probably of cheirolepidiaceous affinity, were -19.0%. These high values are in accordance with inferred ecological conditions for the fossil plants. They may suggest a tendency for C₄,-like photosynthesis, although the data are equivocal. Higher values (-17.3%) clearly falling outside the C₃, range were, however, obtained from a single lignite fragment of Late Cretaceous (Maastrichtian) age. The nature of this plant fragment is unknown, but the result suggests that C₄-like photosynthesis was present at least in some latest Cretaceous vegetation. A hadrosaurian dinosaur with well-preserved collagen-like organic matter from the same deposit showed δ¹³C values around-16%, which also suggests the presence of CAM or even C₄ plants in the latest Cretaceous. □Carbon isotopic abundances, δ¹³C values, dinosaurs, plants, photosynthetic pathways, Mesozoic.