Sixteen new simple sequence repeat markers from Brassica juncea expressed sequences and their cross‐species amplification

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 16 expressed sequence tags (EST)‐SSR markers from Brassica juncea and their cross‐amplification across Brassica species. Sixteen primer pairs were assessed for polymorphism in all genomes of the diploid and amphidiploid Brassica species. The markers show reliable amplification, considerable polymorphism and high transferability across species, demonstrating the utility of EST‐SSRs for genetic analysis of brassicas.     

Analysis of Time-Varying Biological Data Using Rainflow Cycle Counting

A wide range of biological investigations lead to time-history data. The characterization of such data can be difficult particularly in the presence of signal noise or superimposed signals. Several methods are described which can be brought to bear including FFT, thresholding, peak counting, and range counting. However, each of these approaches has significant disadvantages. In this paper we describe a novel method, known as rainflow cycle counting, for characterizing time varying biological time-history data in terms of spiking or oscillation amplitude and frequency. Rainflow counting is a straightforward algorithm for identifying complete cycles in the data and determining their amplitudes. The approach is simple, reliable, easily lends itself to automation, and robust even in the presence of superimposed signals or background noise. After describing the method, its use and behavior are demonstrated on three sample histories of intracellular calcium concentration in chondrocytes exposed to fluid shear stress. The method is also applied to a more challenging data set that has had an artificial random error included. The results demonstrate that the rainflow counting algorithm identifies signal oscillations and appropriately determines their amplitudes even when superimposed or distorted by background noise. These attractive properties make rainflow counting a powerful approach for quantifying and characterizing biological time histories.     

Effects of elevated CO2 and/or O3 on growth, development and physiology of wheat (Triticum aestivum L.)

Two cultivars of spring wheat (Triticum aestivum L. cvs. Alexandria and Hanno) and three cultivars of winter wheat (cvs. Riband, Mercia and Haven) were grown at two concentrations of CO₂ [ambient (355 pmol mol^?1) and elevated (708 μmol mol^?1)] under two O₃ regimes [clean air (< 5 nmol mol^?1 O₃) and polluted air (15 nmol mol^?1 O₃ at night rising to a midday maximum of 75 nmol mol^?1)] in a phytotron at the University of Newcastle-upon-Tyne. Between the two-leaf stage and anthesis, measurements of leaf gas-exchange, non-structural carbohydrate content, visible O₃ damage, growth, dry matter partitioning, yield components and root development were made in order to examine responses to elevated CO₂ and/or O₃. Growth at elevated CO₂ resulted in a sustained increase in the rate of CO₂ assimilation, but after roughly 6 weeks' exposure there was evidence of a slight decline in the photosynthetic rate (c.-15%) measured under growth conditions which was most pronounced in the winter cultivars. Enhanced rates of CO₂ assimilation were accompanied by a decrease in stomatal conductance which improved the instantaneous water use efficiency of individual leaves. CO₂ enrichment stimulated shoot and root growth to an equivalent extent, and increased tillering and yield components, however, non-structural carbohydrates still accumulated in source leaves. In contrast, long-term exposure to O₃ resulted in a decreased CO₂ assimilation rate (c. -13%), partial stomatal closure, and the accumulation of fructan and starch in leaves in the light. These effects were manifested in decreased rates of shoot and root growth, with root growth more severely affected than shoot growth. In the combined treatment growth of O₃-treated plants was enhanced by elevated CO₂, but there was little evidence that CO₂ enrichment afforded additional protection against O₃ damage. The reduction in growth induced by O₃ at elevated CO₂ was similar to that induced by O₃ at ambient CO₂ despite additive effects of the individual gases on stomatal conductance that would be expected to reduce the O₃ flux by 20%, and also CO₂-induced increases in the provision of substrates for detoxification and repair processes. These observations suggest that CO₂ enrichment may render plants more susceptible to O₃ damage at the cellular level. Possible mechanisms are discussed.     

Predation by Australian magpies (Gymnorhina tibicen) on pasture invertebrates: Are non-territorial birds less successful?

Diet composition and prey intake rates of Australian magpies in a New Zealand population were investigated to determine whether flocking, non-territorial birds were less successful predators of pasture invertebrates than territorial birds. Time-activity budgets showed that flock magpies foraged throughout the day during February and March, indicative of a prey shortage at that time. Prey abundance was therefore measured in the autumn months but there was no evidence of a large quantitative difference in the food supply of flock and territorial magpies. Significantly fewer invertebrates were collected from pitfall traps in the flock foraging area, but these were counterbalanced by significantly more scarab beetle larvae and more flying insects, obtained by sweep-netting. When compared with territorial magpies, flock birds exhibited similar peck rates, prey intake rates, and earthworm intake rates. While there were qualitative differences in the diets of flock and territorial magpies, determined by faecal analysis, five of seven prey items analysed were captured in the same relative proportions by the flock and territorial birds. Earthworms exceeded their relative availability in the diets of flock birds, and more scarab larvae were found in the diets of territorial magpies. Non-territorial magpies were therefore no less successful than territorial birds during the autumn, and it is suggested that the function of flocking behaviour may eventually be discovered through consideration of why non-territorial birds never occur as solitary individuals, rather than emphasizing comparisons with territorial magpies.     

Revision of the genus Clathrina (Porifera, Calcarea)

The genus Clathrina has one of the most difficult systematic arrangements in the Porifera, Class Calcarea. Few morphological characters can be used to describe its species, and the systematics and the geographical distribution of its species have changed several times, according to the point of view of the systematists. 'Lumpers' consider that clathrinas are morphologically plastic, while 'splitters' believe that even slight morphological differences should be considered sufficient to distinguish between species. The morphology of several specimens/species of Clathrina , including the type species, when possible, was studied and used to produce the first revision of this genus. Using results obtained from previous morphological and molecular studies, the morphological characters were chosen and analysed in all studied specimens. In total, 43 species were found, nine of which are new to science. These results agree with the viewpoint that morphological characters such as type and distribution of spicules, size of actines, spines, anastomosis of the cormus, organization of the osculum and presence of granules in cells, are useful when establishing the taxonomy of the genus.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 1−62.     

Pathways of Uptake and Accumulation of Sugars in Tomato Fruit

The route of sucrose unloading from the conducting tissue, theregulation of sucrose hydrolysis and the uptake and subsequentmetabolism of sugars were investigated in the rapidly growingtomato fruit. During the first two weeks of fruit enlargement, the vacuoleaccounted for more than 85% of the protoplast volume and theintercellular space accounted for 20% of the fruit placentaltissue. The plasmodesmatal frequency was highest between phloemparenchyma cells and lowest between phloem sieve cells and phloemparenchyma. The total invertase activity was about 8 µmolglucose g^–1 d. wt min^–1 during the rapid growingperiod and increased six-fold at ripening. The wall-bound invertaseaccounted for less than 11% of the total activity. Invertaseactivity increased with increasing sucrose concentrations (upto 50 mM) in the incubation medium, but decreased at higherconcentrations. Sucrose synthase activity could only be detectedwhen fruit was older than 19 d. The uptake and metabolism of sugars by fruit cells were investigatedby incubation of fruit slices with ¹⁴C-sugars for 3 h. The uptakeof sucrose increased with the sucrose concentration up to 200mM. The rate of glucose uptake and its conversion to the ethanol-insolublefraction were higher than those of sucrose. The uptake of sucrosedid not compete with that of glucose or vice versa, providedthe osmotic potential of the incubation solution was maintainedconstant. The uptake of sucrose was not inhibited by metabolicinhibitors such as PCMBS, CCCP, sodium azide or vanadate. TheATPase activity in the fruit tissue was low. These findings did not identify conclusively the mode of sucroseunloading. However, the uptake of sugars by fruit cells is non-specificand does not appear to require a membrane carrier or plasmalemmaATPase to provide energy for sucrose uptake. Fruit, invertase, Lycopersicon esculentum, phloem unloading, plasmodesmata, sucrose     

Molecular approaches to nontoxic antifouling

Summary

A consequence of environmental and human health concerns arising from the use of toxic metals in marine antifouling coatings has been to recognise the need for a nontoxic alternative to fouling control. Recent research has focused on two approaches to this problem: the development of (a) foul-release coatings that work on the principle of either low surface free energy or coating ablation, and (b) coatings that incorporate a compound(s) that is nontoxic, or at least environmentally benign, that will deter fouling. Here we discuss the nature of the fouling problem and a new technology that is emerging to address it. The use of natural marine products and of analogues to these compounds holds considerable promise and is an area of intense research. It is recognized, however, that a melding of the technologies of foul-release and foul-deterrence may be required to develop broad spectrum, nontoxic antifouling coatings. This approach may more closely reflect antifouling strategies adopted by marine organisms that maintain a foul-free surface.