Growth dynamics and biomass allocation of Eleocharis sphacelata at different water depths: observations, modeling, and applications

Imbalanced biomass allocation patterns in emergent aquatic plants to above and below-ground structures as a response to climatic variations and water depth were investigated on the basis of observation of three stable homogeneous populations established under different water regimes and climatic environments in Goulburn and Ourimbah, New South Wales, Australia, from August 2003 to December 2004. The growth of shoots depended on water inundation-drawdown patterns and climatic variations. Shoot density was greater in shallow water but with shorter shoot length and less maximum above-ground biomass density than for plant stands in deep water. Deep-water populations attained higher below-ground biomass with higher above to below-ground biomass ratio than for the shallow-water population. Translocation of carbohydrate reserves between above and below-ground organs in deep-water populations were mostly downward throughout the year whereas the depletion–recharge pattern varied seasonally in shallow water populations. Shoots of deep-water populations grew year-round whereas in shallow water shoots died off after recession of the water level with no re-growth afterward, showing that Eleocharis sphacelata is better adapted to deep water and is stressed under shallow-water conditions. A mathematical model was formulated to describe the growth patterns of E. sphacelata and subsequently to predict the effect of water depth on production. Model simulations are in satisfactory agreement with observed patterns of growth. The model also predicts that maximum production decreases sharply with increasing water depth.     

Characterization of microsatellite markers in peach [Prunus persica (L.) Batsch]

Microsatellites have emerged as an important system of molecular markers. We evaluated the potential of microsatellites for use in genetic studies of peach [Prunus persica (L.) Batsch]. Microsatellite loci in peach were identified by screening a pUC8 genomic library, a λZAPII leaf cDNA library, as well as through database searches. Primer sequences for the microsatellite loci were tested from the related Rosaceae species apple (Malus×domestica) and sour cherry (Prunus cerasus L.). The genomic library was screened for CT, CA and AGG repeats, while the cDNA library was screened for (CT)_n- and (CA)_n-containing clones. Estimates of microsatellite frequencies were determined from the genomic library screening, and indicate that CT repeats occur every 100 kb, CA repeats every 420 kb, and AGG repeats every 700 kb in the peach genome. Microsatellite- containing clones were sequenced, and specific PCR primers were designed to amplify the microsatellite- containing regions from genomic DNA. The level of microsatellite polymorphism was evaluated among 28 scion peach cultivars which displayed one to four alleles per primer pair. Five microsatellites were found to segregate in intraspecific peach-mapping crosses. In addition, these microsatellite markers were tested for their utility in cross-species amplification for use in comparative mapping both within the Rosaceae, and with the un- related species Arabidopsis thaliana L. Received: 18 June 1999 / Accepted: 6 December 1999     

Anti-Rhinosporidial Antibody Levels in Patients with Rhinosporidiosis and in Asymptomatic Persons,in Sri Lanka

The only report hitherto, from India in 1982, on anti-rhinosporidial antibody levels in patients with rhinosporidiosis recorded that antibody was not detected in Indian patients. The present report describes the use of the dot-ELISA assay of serum anti-rhinosporidial IgG, IgM and IgA and salivary sIgA in patients with diverse clinical presentations, in rural asymptomatic persons who had bathed in ground waters that probably harboured the causative pathogen, Rhinosporidium seeberi, and in laboratory persons who were exposed to R. seeberi. Ultrasonic extracts of purified endospores and sporangia of R. seeberi were used as antigen. The geometric mean (reciprocal) titres of serum antibody detected in patients were IgM 142.1, IgG 178.5, IgA 84.6, with ranges of 0-640, 30-960 and 0-160 respectively, salivary sIgA titres ranged from 0 to 18 with a mean of 4.6. The levels of antibody had no correlation with the site, the number of sporangia, duration and recurrence of the disease. Asymptomatic persons from the same endemic area as patients showed mean titres of IgM 89.6, IgG 69.1, IgA 95.5, with salivary sIgA titres of 3.1. Asymptomatic personnel who had been working in a laboratory where rhiniosporidial work was being done, showed mean titres of 169.6 IgM, 62.8 IgG, and 6.5 salivary sIgA. These results indicate that an anti-rhinosporidial antibody response occurs in rhinosporidial patients, as well as in asymptomatic persons who were exposed to R. seeberi in the environment. Anti-R. seeberi antibody does not appear to be protective in rhinosporidiosis since appreciable titres were present in patients with recurrent, single, multiple or disseminated lesions of long duration.     

Decomposition of aboveground and belowground organs of wild rice (Zizania latifolia): mass loss and nutrient changes

Decomposition of aboveground and belowground organs of the emergent macrophyte Z.latifolia was investigated using a litterbag technique for a period of 359 days in a freshwater marsh in Japan. Aboveground parts were classified into: leaves, sheaths and stems. Belowground parts were classified into: horizontal rhizomes (new rhizome, hard rhizome, soft rhizome) and vertical rhizome (stembase). The decay rate (k) was 0.0036 day⁻¹, 0.0033 day⁻¹ and 0.0021 day⁻¹ for leaves, sheaths and stems, respectively. For belowground parts, the decay rate varied considerably from 0.0018 day⁻¹ to 0.0079 day⁻¹, according to differences in the initial chemical compositions of rhizomes. After 359 days of decay, new rhizomes lost 94% of their original dry mass, compared with a loss of 48–84% for the other rhizomes. There was a significant positive relationship between litter quality and decay rate for horizontal rhizomes. For the new rhizomes, which had an internal nitrogen content of 24.2 mg N g⁻¹ dry mass, the mass loss was 40% higher than that of soft rhizomes, which had an internal N content of 9.8 mg N g⁻¹ dry mass. Over the period of 359 days, the nitrogen concentration in all rhizome types decreased to levels lower than initial values, but the phosphorus concentration remained constant after an initial leaching loss. Most nitrogen and phosphorus were lost during the first 45 days of decay. Changes in carbon to nitrogen (C:N) and carbon to phosphorus (C:P) ratios basically followed inversed trends of the nitrogen and phosphorus concentrations.     

Effects of satiation on feeding and swimming behaviour of planktivores

Hunger affects the feeding and swimming behaviour in fish. After 36 h of food deprivation, the feeding and swimming behaviour of Pseudorasbora parva (Cyprinidae) was studied under different prey densities (0.5, 1, 2, 5, 10 and 25 of Daphnia pulex per liter). The initial feeding rates showed marked variations in relation to prey availability. Under high prey densities, the initial feeding rate of fish was higher and subsequently decreased faster, when compared to those feeding under low prey densities. At higher prey densities, two factors were involved: that of higher prey encounter rates and also the attainment of food satiation at a faster rate. Across all prey densities, the feeding rates of fish reached a plateau after satiation. The swimming speed of fish was found to be negatively related to the prey density and a significant change in swimming speed was noted as being directly related to the level of satiation. It was found that the increasing satiation level greatly influenced the handling time and reactive volume of predator, which finally caused reduced feeding rates.     

Seasonal patterns of carbohydrate translocation and synthesis of structural carbon components in <Emphasis Type="Italic">Typha angustifolia</Emphasis>

Quantitative studies of material budgets and resource allocation patterns of emergent plants are needed to fully understand nutrient and carbon cycling in wetlands. Whole-plant translocation patterns of nonstructural carbohydrates and synthesis of structural carbon were documented using two (shallow and deepwater) populations of Typha angustifolia in floodplain habitats of the Arakawa River, Japan. Monthly and bimonthly measurements of the concentrations of total carbon, non-structural carbohydrates, and water-soluble carbohydrates, as well as, estimates of standing stocks of aboveground (AG) and belowground (BG) biomass for both populations from 2002 to 2004 are described here. Annual patterns of carbon gain, rates of carbohydrate translocation between AG and BG organs, and rates of synthesis of structural carbon were estimated. Upward translocation supported all AG production for approximately 30 days. Afterward, the fraction of AG production supported by upward translocation decreased linearly with time, and completely diminished by Day 80 (counted from first day of growth; March 15). At Day 80, material translocation was directed downward and the percentage of downward translocation relative to AG net production increased until Day 170; there was a vigorous increase in downward translocation prior to senescence. In early summer (Day 80–110), more than half of the translocated materials were transformed into structural components, but by Day 125 only 30% was synthesized into total structural carbohydrates. Prior to senescence, there was a greater percentage of nonstructural carbohydrates in the rhizomes. Across the growing season (Day 60–153), the total amount of downward translocation was found to be proportional to AG production and the quantitative evaluation of the carbon budget shed further insight into the translocation process of this rhizomatous aquatic plants. In addition, insights on the differences between shallow and deepwater populations were gained. Especially, the deepwater population supported a higher fraction of vertical rhizomes compared to individuals sampled from the shallow water population. Handling editor: S. M. Thomaz.     

Genus-Wide Comparative Genomics of Malassezia Delineates Its Phylogeny,Physiology, and Niche Adaptation on Human Skin

Malassezia is a unique lipophilic genus in class Malasseziomycetes in Ustilaginomycotina, (Basidiomycota, fungi) that otherwise consists almost exclusively of plant pathogens. Malassezia are typically isolated from warm-blooded animals, are dominant members of the human skin mycobiome and are associated with common skin disorders. To characterize the genetic basis of the unique phenotypes of Malassezia spp., we sequenced the genomes of all 14 accepted species and used comparative genomics against a broad panel of fungal genomes to comprehensively identify distinct features that define the Malassezia gene repertoire: gene gain and loss; selection signatures; and lineage-specific gene family expansions. Our analysis revealed key gene gain events (64) with a single gene conserved across all Malassezia but absent in all other sequenced Basidiomycota. These likely horizontally transferred genes provide intriguing gain-of-function events and prime candidates to explain the emergence of Malassezia. A larger set of genes (741) were lost, with enrichment for glycosyl hydrolases and carbohydrate metabolism, concordant with adaptation to skin’s carbohydrate-deficient environment. Gene family analysis revealed extensive turnover and underlined the importance of secretory lipases, phospholipases, aspartyl proteases, and other peptidases. Combining genomic analysis with a re-evaluation of culture characteristics, we establish the likely lipid-dependence of all Malassezia. Our phylogenetic analysis sheds new light on the relationship between Malassezia and other members of Ustilaginomycotina, as well as phylogenetic lineages within the genus. Overall, our study provides a unique genomic resource for understanding Malassezia niche-specificity and potential virulence, as well as their abundance and distribution in the environment and on human skin.     

Root site occupancy modelling of young New Zealand native plants: implications for soil reinforcement

Plants are widely used in soil conservation to control and prevent erosion on hillslopes and on riverbanks. Previous research has shown the mechanical root reinforcement on soil stability can be considerable. However, land and forest managers still require information and simple tools to enable them to determine how and when a species becomes effective in terms of soil stabilisation. This paper uses root length data from a trial of young New Zealand trees and shrubs to develop a simple model to account for the spatial occupancy of a planting site by roots, and by implication their potential strength contribution to soil reinforcement. It is developed by calculating root surface area in contact with the soil to obtain an effective radius of the root spread about the stem. The approach generates a set of coefficients that are unique to a species for a given site which can then be used in the generalised model to predict root site occupancy, which is taken as a proxy for when soil reinforcement is attained. This information can then be used to assess effectiveness of different species mixes in planting plans.     

Synthesis and characterization of a small analogue of the anticancer natural product leinamycin

Leinamycin (1) is a Streptomyces-derived natural product that displays nanomolar IC₅₀ values against human cancer cell lines. In the work described here, we report the synthesis and characterization of a small leinamycin analogue 19 that closely resembles the ‘upper-right quadrant’ of the natural product, consisting of an alicyclic 1,2-dithiolan-3-one 1-oxide heterocycle connected to an alkene by a two-carbon linker. The results indicate that this small analogue contains the core set of functional groups required to enable thiol-triggered generation of both redox active polysulfides and an episulfonium ion intermediate via the complex reaction cascade first seen in the natural product leinamycin. The small leinamycin analogue 19 caused thiol-triggered oxidative DNA strand cleavage in a manner similar to the natural product, but did not alkyate duplex DNA effectively. This highlights the central role of the 18-membered macrocycle of leinamycin in driving efficient DNA alkylation by the natural product.     

Strong electronic charge as an important factor for anticancer activity of chitooligosaccharides (COS)

Even though several studies report the importance of chitosan derivatives for their anticancer activity, no clear information is available to describe the relationship between their charge properties and observed activities. In this research, differently charged chitooligosaccharide (COS) derivatives were synthesized and their anticancer activities were studied using three cancer cell lines, HeLa, Hep3B and SW480. Neutral red and MTT cell viability studies revealed that, highly charged COS derivatives could significantly reduce cancer cell viability, regardless to the positive or negative charge. Further, fluorescence microscopic observations and DNA fragmentation studies confirmed that the anticancer effect of these highly charged COS derivatives were due to necrosis. However, the exact molecular mechanism for anticancer activity of strongly charged COS compared to their poorly charged counterparts is not clear.