The α-gliadin gene family. I. Characterization of ten new wheat α-gliadin genomic clones, evidence for limited sequence conservation of flanking DNA, and Southern analysis of the gene family

 A detailed study of the organization of the wheat α-gliadin gene family is described. In the first stage of this study recombinant libraries of sufficient size and quality were constructed to allow examination of large, closely-related, gene families. A large number of α-gliadin clones were then isolated in a partial screen of these libraries. A set of these clones were sequenced and ten new gene sequences are now reported. Including these new sequences, 20 of the 27 known α-gliadin genomic and cDNA sequences are from cv Cheyenne, making this cultivar the best studied for gliadin family organization. An analysis of the DNA flanking the coding regions shows divergences which may indicate the functional ends of the α-gliadin genes. High-resolution Southern analyses on DNA from aneuploid and chromosome-substitution lines allow most of the 20 distinct α-gliadin HindIII restriction fragments in cvs Cheyenne and Chinese Spring to be assigned to specific genomes. It is estimated that as many as 150 α-gliadin genes occur in the cultivar Cheyenne, and the limitations of such estimates are discussed. Received: 1 October 1996 / Accepted: 20 December 1996     

Filament lumachelle on top of Middle Jurassic oolite limestones: event deposits marking the drowning of a Tethysian carbonate platform (Subbetic,southern Spain)

Bioclastic accumulations often occur on top of Tethysian carbonate platforms and crinoids are a common constituent of these bioclastic deposits on Lower and Middle Liassic carbonate platforms. In contrast, the relevant literature contains few examples in which the main constituent of the lumachels is thin-shelled bivalves (filaments). This paper presents a study of a filament lumachelle cropping out on top of a Middle Jurassic carbonate platform. The carbonate platform is represented by the Jabalcuz Formation, found in one of the northernmost Subbetic units (south of Jaén city). The lumachelle marks the demise of the carbonate platform and has special features that characterize the drowning phase. This process has been related with the syn-rift extensional tectonics associated to the opening of the Tethys westwards. Stratigraphically, the lumachelle occurs on top of shallow-water oolite limestones (Middle Jurassic) and is overlain by radiolarian-rich pelagic and resedimented deposits (Latest Callovian–Oxfordian). It occurs as a body (about 1.5 km wide and up to 8 m thick) made up entirely of densely packed thin bivalve shells. A remarkable feature of the bivalve shell beds is stromatolite-like crumpled lamination at the outcrop. The observations made at the outcrop scale, by microscope under transmitted light, and by cathodoluminiscence favor a diagenetic origin for this striking structure. Other hypotheses, such as its possible relation with seismicity, cannot be confirmed. The filaments would have filled one of the former basins that originated in relation with syn-rift fault-block tectonics leading to the demise of the carbonate platform. Tectonics was one of the main factors setting in motion a carbonate productivity crisis and the inhibition of a diverse benthic community. Once production failed in the carbonate factory, storms and probably hurricanes as well, swept shell deposits from the shallowest areas of the shallow-water carbonate platform and accumulated them in a coevally formed small half-graben basin. At least three main depositional stages can be differentiated in the fill of this half-graben basin, which was a sediment trap for the accumulation and preservation of the tiny bivalve shells against ebb surges. The massive accumulation of valves, the shortage of micrite around the filaments, outcrop morphology and facies relationships, along with regional geology, are among the arguments supporting this interpretation.     

An improved method for Southern DNA and Northern RNA blotting using a Mupid-2 Mini-Gel electrophoresis unit

An improved method for Southern DNA and Northern RNA blotting using the Mupid-2 Mini-Gel System is described. We get sharp and clear bands in Southern and Northern blotting after only 30 min short gel electrophoresis instead of the several hours large gel electrophoresis of conventional methods. The high electrical voltage with a pulse-like current of the Mupid-2 Mini-Gel System also allows reduction of the amount of formaldehyde, a harmful reagent, from the gel running buffer in RNA blotting. This minor modification of DNA and RNA blotting technique enables us to perform the complete experimental procedure more quickly economically in less space, than conventional Southern and Northern blotting, as well as using an extremely small amount of formaldehyde in RNA blotting.     

King Penguins adjust foraging effort rather than diet when faced with poor foraging conditions

The links between foraging success, foraging effort and diet in a myctophid specialist seabird, the King Penguin Aptenodytes patagonicus, were investigated during seven breeding seasons using tracking and isotopic data. Despite the variable foraging conditions encountered by the birds, isotopic signatures (a proxy for diet) were invariable throughout the study. On the other hand, penguins stayed longer at sea when the foraging success indices (i.e. prey capture attempts per day and mass gained per day) were low. Although King Penguins can compensate for low prey capture rates by increasing foraging effort, their specialist diet during reproduction makes the species particularly sensitive to prey availability, with its conservation tightly linked to its main prey.     

香港深涌黄地峒遗址试掘简报

深涌黄地峒遗址是香港首次发现的旧石器时代晚期遗址。初步调查、试掘后认为,这是一处打制石器加工场,其范围之大(南北长约300m、东西宽约150m)和石制品密度之高(试掘10m2,出土及采集石器3261件)实属罕见。出土石器种类比较丰富,旧石器加工技术大部分在此都能见到。该遗址的进一步发掘和研究,对了解和解决岭南以及中国南方地区旧石器文化发展的问题将有大帮助。     

Movement of oceanic fronts south of Australia during the last 10 ka: interpretation of calcareous nannoplankton in surface sediments from the Southern Ocean

Preservation of calcareous nannoplankton in surface sediment samples from the Southern Ocean south of Australia and adjacent to New Zealand record a single assemblage. The dominant species are Emiliania huxleyi, Gephyrocapsa muellerae, Calcidiscus leptoporus, Helicosphaera carteri and Coccolithus pelagicus. The assemblage varies little in abundance and diversity with minor correlation to present-day overlying surface water masses and oceanic fronts. Increase in abundance of H. carteri and C. pelagicus in the region of the Subtropical Front may reflect higher nutrients associated with this front. The assemblage, although altered by dissolution, represents a warmer climatic interval than present-day with the presence of preferentially dissolved, warm-water species preserved as far south as the Polar Front. The presence of warm-water species under sub-Antarctic waters at the Polar Front is interpreted as a relic population from the Holocene climatic optimum of 10–8 ka. The absence of coccoliths in sediments poleward of the Polar Front suggests an equatorward shift of this front following the climatic optimum, resulting in increased productivity of siliceous phytoplankton associated with the colder waters and increased dissolution of coccoliths. Movement of the Subtropical Front for the same interval is not recorded in the preserved coccoliths. The more heavily calcified form of E. huxleyi which dominates the living assemblage north of the Subtropical Front is subject to dissolution in this region and is poorly preserved in the sediment assemblage.     

Monitoring of in planta gene expression for xylan degradation and assimilation in the maize pathogen Bipolaris maydis

Swift and efficient onset of feeding on host tissue by phytopathogenic fungi is a requisite event for their successful infection and propagation. Necrotrophic fungi colonizing host cell walls appear to obtain carbon and energy sources from plant wall degradants, but what they actually utilize for nutrition after host invasion remains unclear. Here we focus on plant wall xylan, the major hemicellulosic polysaccharide in cereal plants, and study its participation in post-invasion nutrition of the maize necrotrophic pathogen Bipolaris maydis (syn: Cochliobolus heterostrophus). Using a fluorescence reporter assay, we demonstrated that a B. maydis β-xylosidase gene, BmXyp1, is strongly upregulated at the beginning of infection, specifically within invading hyphae. Additionally, our time-course measurements of mRNA expression during maize infection revealed that xylan degradation and assimilation are concomitantly induced during an early infection stage. These findings suggest that this fungus can access xylan degradants as an early in planta nutrient source after host penetration; however, mutant strains deficient in xylan-assimilation ability still retained virulence, although the lesion size was decreased as compared with the wild-type strain. Overall, we conclude that xylan degradation and assimilation by B. maydis are initial post-invasion events but do not play an essential role in fungal nutrient acquisition.     

Maternal deposition of yolk corticosterone in clutches of southern rockhopper penguins (Eudyptes chrysocome chrysocome)

High corticosterone levels can have deleterious effects in developing avian embryos and chicks. Therefore, it may be adaptive for avian mothers to reduce corticosterone transfer to their eggs. However, until now, data about the active or/and passive role of mothers in corticosterone transfer to eggs are inconclusive. Here, we study maternal investment into A- and B-eggs of southern rockhopper penguins (Eudyptes chrysocome chrysocome). This species exhibits reversed hatching asynchrony and provides a unique model to test whether there is a strategic investment in corticosterone favoring the B-chick, which is most likely to survive. We found that rockhopper penguins had the highest yolk concentrations of any wild bird species studied so far. Contrary to our expectations, B-eggs had more yolk corticosterone both in concentration and in quantity than A-eggs, independently of the laying period and the level of human disturbance. Additionally, females deposited more yolk corticosterone in their eggs when they were disturbed. However, this disturbance effect was particularly strong for A-eggs and for late-laid eggs. The present data support neither the predictions for an active regulation nor for a passive deposition, and hormone deposition mechanisms still need to be explored. The adaptive value, if any, of high yolk corticosterone is presently unknown.     

The response of leaf morphology to irradiance depends on altitude of origin in Nothofagus cunninghamii

Leaf morphology varies reliably with increasing altitude in many species, and this is generally considered to be related to temperature. Changes in irradiance with elevation may confound any relationships between a morphological character and altitude, particularly if altitude of origin affects the response to irradiance. Here we describe the interaction between irradiance and altitude of origin on leaf morphology of Southern beech, Nothofagus cunninghamii. Cuttings from each of four altitudes were grown in a glasshouse under full sunlight or 50% shade, and leaf morphology was related to irradiance, altitude of origin and accession. There was a significant interaction between irradiance and altitude of origin for leaf length, width, thickness, area, weight, specific leaf area and stomatal density. There was no effect of altitude on leaf length to width ratio or stomatal index, nor was there an interaction between irradiance and altitude of origin for these variables. These results show that the altitude of origin of a plant has an overriding impact on the leaf morphological response to irradiance. This must be considered in climatic reconstructions.