Functional properties of the anaerobic responsive element of the maize Adh1 gene

The functional properties of the anaerobic responsive element (ARE) of the maize Adh1 gene have been analysed using a transient expression assay in electroporated maize protoplasts. The ARE functions in both orientations although inversion of the ARE sequence relative to the TATA box element produces slightly weaker promoter activity under anaerobic conditions and elevated expression under aerobic conditions. Promoter activity under anaerobic conditions is proportional to the number of complete ARE sequences in the Adh1 promotor. The ARE contains two sub-regions and dimers of sub-region II are as efficient as the wild-type sequence in activating gene expression under anaerobic conditions. However, sub-region I dimers do not appear capable of inducing gene expression in response to anaerobic stress. We conclude that sub-region II is essential for anaerobic induction of gene expression. Reporter gene expression remains constant when the spacing between sub-regions of the ARE is increased up to at least 64 bp, but increased spacing of 136 bp or greater abolishes expression in both aerobic and anaerobic conditions, indicating that a close association of the two sub-regions is required both for anaerobic responsiveness and for maximal levels of aerobic gene expression. When the ARE is placed upstream of position –90 of the CaMV 35S promoter, the ARE produces a high level of expression in both aerobic and anaerobic conditions. The general enhancement of gene expression driven by the hybrid ARE/35S promoter in aerobic conditions requires an intact sub-region II motif since mutation or deletion of sub-region II from the hybrid promoter reduces the level of expression to that observed for the truncated 35S promoter alone. In addition, mutation of the sub-region I sequences in the ARE/35S hybrid promoter does not significantly reduce expression in aerobic conditions, relative to pARE/35S(-90), suggesting that sub-region I does not contribute to this general enhancer function.     

稀土元素对甜菜种子萌发,幼苗生长及块根产量的影响

本文研究了稀土元素对甜菜的生物效应。结果表明,稀土元素可显著地提高种子萌发率,促进幼苗生长,增加幼苗根系活力、叶片净光合速率与块根产量,并明显地降低了甜菜叶片细胞膜在低温下的透性,即提高了叶片的抗寒力。     

Phenology of Festuca pallescens in relation to topography in north-western Patagonia

Abstract. The phenological changes in populations of Festuca pallescens (St. Yves) Parodi at different topographic positions and exposure along an altitudinal gradient (600 - 1100 m) were investigated during two growing seasons in northwestern Patagonia. Stepwise multiple regression analysis was used to describe the relationship between phenology and environment during the entire growing season. Analysis of variance was also performed at each sample date to detect significant environmental factors influencing phenology at different sites. The sum of maximum air temperatures was identified as the environmental variable best correlated with the seasonal variation of phenological events of Festuca pallescens over the period of two growing seasons, explaining 93.2 % of the total variance. Significant differences between sites were observed at each sample date. Main effects of altitude and topographic position and two-way interactions between altitude and topographic position, and topographic position and exposure were also detected as significant. Phenology was delayed at increased altitude. Differences in phenology between topographic sites at the same altitude were not detected during the entire growing season and were only observed in the reproductive phase. At this time, the phenology was significantly delayed at high topographic positions on the slopes as compared with low and mid positions. At high altitudes in the valley (950 m a. s. 1.), where steep slopes and humid conditions prevail, phenology was delayed on western exposures and low positions. The results adequately summarize and quantify the effect of spatial and temporal environmental variation on the phenological development of Festuca pallescens in northwestern Patagonia.     

Pegasus, a small terminal inverted repeat transposable element found in the white gene of Anopheles gambiae

Pegasus, a novel transposable element, was discovered as a length polymorphism in the white gene of Anopheles gambiae. Sequence analysis revealed that this 535 bp element was flanked by 8 bp target site duplications and 8 bp perfect terminal inverted repeats similar to those found in many members of the Tcl family. Its small size and lack of long open reading frames preclude protein coding capacity. Southern analysis and in situ hybridization to polytene chromosomes demonstrated that Pegasus occurs in approximately 30 copies in the genomes of An. gambiae and its sibling species and is homogenous in structure but polymorphic in chromosomal location. Characterization of five additional elements by sequencing revealed nucleotide identities of 95% to 99%. Of 30 Pegasus-containing phage clones examined by PCR, only one contained an element exceeding 535 bp in length, due to the insertion of another transposable element-like sequence. Thus, the majority, if not all, extant Pegasus elements may be defective copies of a complete element whose contemporary existence in An. gambiae is uncertain. No Pegasus-hybridizing sequences were detected in nine other anophelines and three culicines examined, suggesting a very limited taxonomic distribution.     

Controlled experiments of habitat fragmentation: a simple computer simulation and a test using small mammals

Habitat fragmentation involves a reduction in the effective area available to a population and the imposition of hard patch edges. Studies seeking to measure effects of habitat fragmentation have compared populations in fragments of different size to estimate and area effect but few have examined the effect of converting open populations to closed ones (an effect of edges). To do so requires a shift in spatial scope-from comparison of individual fragments to that of fragmented versus unfragmented landscapes. Here we note that large-scale, controlled studies of habitat fragmentation have rarely been performed and are needed. In making our case we develop a simple computer simulation model based on how individual animals with home ranges are affected by the imposition of habitat edges, and use it to predict population-level responses to habitat fragmentation. We then compare predictions of the model with results from a field experiment on Peromyscus and Microtus. Our model treats the case where home ranges/territories fall entirely within or partially overlap with that of sample areas in continuous landscapes, but are restricted to areas within habitat fragments in impacted landscapes. Results of the simulations demonstrate that the imposition of hard edges can produce different population abundances for similar-sized areas in continuous and fragmented landscapes. This edge effect is disproportionately greater in small than large fragments and for species with larger than smaller home ranges. These predictions were generally supported by our field experiment. We argue that large-scale studies of habitat fragmentation are sorely needed, and that control-experiment contrasts of fragmented and unfragmented microlandscapes provide a logical starting point.     

Sequence analysis of the 5′-flanking region of the gene encoding human N-acetylglucosaminyltransferase III

We have isolated and characterized the immediate (1651 bp) 5′-flanking region of the gene (GnT-III) encoding N-acetylglucosaminyltransferase III (GnT-III) from a human placental genomic library. Analysis of promoter elements shows a similarity to the 5′-flanking region of murine 1,4-galactosyltransferase. The sequence lacks obvious TATA elements and CCAAT boxes; however, putative regulatory sites, including 2 potential cAMP-response regulatory elements (CRE), 11 insulin-response element consensus sequences (IRE), 7 potential AP-2-binding sites, 2 SP1 consensus sequences (GC boxes) and 2 sequences similar to the half-palindromic glucocorticoid-responsive element (GRE), are present.     

华东植物区系成分与日本植物间的联系

华东和日本两地为东亚地区重组成部分,同属于中国－日本森林植物亚区。两地植区物系成具有较高的相似性。两地共有连香树科（Ｃｒｃｉｄｉｐｈｙｌｌａｃｅａｅ）、三尖杉科（Ｃｅｐｈａｌｏｔａｃｅａｅ）、领春木科（Ｅｕｐｔｅｌｅａｃｅａｅ）、旌节花科ǎ樱簦幔悖瑁酰颍幔悖澹幔澹┑榷翘赜锌啤;腿毡玖降毓灿惺粼迹叮福岸嗍簟Ｈ缌迹ǎ茫颍穑簦铮恚澹颍椋幔⑺荆ǎ模椋螅幔睿簦瑁酰螅⑿」炊ǎ拢澹颍悖瑁     

Black tea,green tea,and tea polyphenols

Previous studies have shown that tea consumption can impair trace element metabolism, particularly iron status, and increase the risk of anemia in humans and animals. More recently, however, evidence has been accumulating to show that, in animals, consumption of green tea or its polyphenols is associated with a reduction of the incidence and severity of a variety of experimentally induced cancers. In this study we have monitored the growth, trace element status, including hematological parameters of weanling rats given either (1) water, (2) 1% black tea, (3) 1% green, tea, or (4) 0.2% crude green tea extract as their sole drinking fluid while consuming diets containing either adequate or low amounts of iron. With the exception of manaanese, none of the trace elements studied (iron, copper, zinc, and manganese) or the hematological indices measured were affected by the type of beverage supplied, even though the polyphenol extract was shown to chelate metals in vitro and all the animals fed the low iron diet were shown to be anemic. There appeared to be an effect of black and green teas on manganese balance in, both the first and last weeks of the study. A lower level of brain managanese was associated with green tea consumption, and a higher level of this element in the kidneys of animals fed black tea. The results demonstrate that both black and green teas and a green tea polyphenol extract do not represent a risk to animals consuming the beverages as their sole fluid intake with respect to iron availability, although the interactions with manganese deserve further study.