Can submerged macrophytes be effective for controlling waterborne phytopathogens in irrigation ponds? An experimental approach using microcosms

Irrigation ponds may act as a source of phytopathogenic species that might infest crops through the irrigation systems. Many studies have shown that submerged macrophytes can improve water clarity by out-competing phytoplankton by means of various mechanisms: favoured phytoplankton-grazing zooplankton, reduced nutrient and light availability, increased sinking losses and the release of allelopathically active substances. However, less information is available on the effects of submerged macrophytes on heterotrophic aquatic organisms such as pathogenic bacteria, fungi or oomycete species. This paper studies the effects of three submerged macrophytes—Chara fragilis, Potamogeton pectinatus and Najas marina—on the viability in water of propagules of two phytopathogenic isolates of the oomycetes Pythium aphanidermatum and Pythium ultimum. Moreover, we tested general antimicrobial properties (against bacteria and fungi in water) for these macrophytes. The results showed clear inhibitory effects of all three macrophytes on bacterial density in water and of C. fragilis on the viability of Pythium. Thus, preserving aquatic vegetation in irrigation ponds (i.e. charophytes), besides its purely environmental interest, may have important agronomic benefits owing to their role as biological control against some phytopathogenic agents.     

Bivalve distribution in hydrographic regions in South America: historical overview and conservation

Based on literature review and malacological collections, 168 native freshwater bivalve and five invasive species have been recorded for 52 hydrographic regions in South America. The higher species richness has been detected in the South Atlantic, Uruguay, Paraguay, and Amazon Brazilian hydrographic regions. Presence or absence data were analysed by Principal Coordinate for Phylogeny-Weighted. The lineage Veneroida was more representative in hydrographic regions that are poorer in species and located West of South America. The Mycetopodidae and Hyriidae lineages were predominant in regions that are richest in species toward the East of the continent. The distribution of invasive species Limnoperna fortunei is not related to species richness in different hydrographic regions there. The species richness and its distribution patterns are closely associated with the geological history of the continent. The hydrographic regions present distinct phylogenetic and species composition regardless of the level of richness. Therefore, not only should the richness be considered to be a criterion for prioritizing areas for conservation, but also the phylogenetic diversity of communities engaged in services and functional aspects relevant to ecosystem maintenance. A plan to the management of this fauna according to particular ecological characteristics and human uses of hydrographic regions is needed.     

Allometric deviations of plasma carotenoids in raptors

Because large species ingest proportionally less food than small ones, it may be predicted that they should incorporate relatively fewer carotenoids to a proportionally equal volume of blood. However, some species may increase their levels of circulating carotenoids by ingesting unusual food. We tested whether the plasma concentration of carotenoids scales to the three‐quarter power of mass in nine predatory and scavenger raptor species. No significant allometric relationships were found due to the unusually high concentrations of carotenoids in the Egyptian Vulture Neophron percnopterus and the Andean condor Vultur gryphus. To assess whether these two species deviate from the allometric rule through the exploitation of unusual sources of carotenoids, or due to a physiological adaptation to improve the uptake of carotenoids, we determined allometric patterns in individuals of these two species kept in captivity with an exclusive diet of flesh. Our results provided support for the allometric rule because the slope of the allometric equation did not differ from a three‐quarter exponent when carotenoid levels of the two outliers were replaced by those of captive birds. This adjustment to the allometric rule suggests a lack of any physiological adaptation to improve the uptake of the low concentrations of carotenoids contained in flesh. Differences between species in carotenoid incorporation into the bloodstream may be ultimately due to contrasting evolutionary history, physiology and associated colour‐signalling strategies, but proximately due to the acquisition of these micronutrients from both usual and unusual dietary sources.     

S100 to receptor for advanced glycation end-products binding assay: Looking for inhibitors

Secreted by tumor and stromal cells, S100 proteins exert their biological functions via the interaction with surface receptors. The most described receptor is the receptor for advanced glycation end-products (RAGE), thereby participating in the S100-dependent cell migration, invasion, tumor growth, angiogenesis and metastasis. Several approaches have been described for determining this interaction. Here we describe an easy, specific and highly reproducible ELISA-based method, by optimizing several parameters such as the binding and blocking buffer, interaction time and concentrations, directed to screen chemical and biological inhibitors of this interaction for S100A4, S100A7 and S100P proteins. The efficiency of the protocol was validated by using well described neutralizing agents of the RAGE receptor and of the S100A4 activity. The methodology described here will allow future works with other members of the S100 protein family and their receptors.     

Lipoic acid entrains the hepatic circadian clock and lipid metabolic proteins that have been desynchronized with advanced age

It is well established that lipid metabolism is controlled, in part, by circadian clocks. However, circadian clocks lose temporal precision with age and correlates with elevated incidence in dyslipidemia and metabolic syndrome in older adults. Because our lab has shown that lipoic acid (LA) improves lipid homeostasis in aged animals, we hypothesized that LA affects the circadian clock to achieve these results. We fed 24 month old male F344 rats a diet supplemented with 0.2% (w/w) LA for 2 weeks prior to sacrifice and quantified hepatic circadian clock protein levels and clock-controlled lipid metabolic enzymes. LA treatment caused a significant phase-shift in the expression patterns of the circadian clock proteins Period (Per) 2, Brain and Muscle Arnt-Like1 (BMAL1), and Reverse Erythroblastosis virus (Rev-erb) β without altering the amplitude of protein levels during the light phase of the day. LA also significantly altered the oscillatory patterns of clock-controlled proteins associated with lipid metabolism. The level of peroxisome proliferator-activated receptor (PPAR) α was significantly increased and acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) were both significantly reduced, suggesting that the LA-supplemented aged animals are in a catabolic state. We conclude that LA remediates some of the dyslipidemic processes associated with advanced age, and this mechanism may be at least partially through entrainment of circadian clocks.     

Connecting the Dots: The Effects of Macromolecular Crowding on Cell Physiology

The physicochemical properties of cellular environments with a high macromolecular content have been systematically characterized to explain differences observed in the diffusion coefficients, kinetics parameters, and thermodynamic properties of proteins inside and outside of cells. However, much less attention has been given to the effects of macromolecular crowding on cell physiology. Here, we review recent findings that shed some light on the role of crowding in various cellular processes, such as reduction of biochemical activities, structural reorganization of the cytoplasm, cytoplasm fluidity, and cellular dormancy. We conclude by presenting some unresolved problems that require the attention of biophysicists, biochemists, and cell physiologists. Although it is still underappreciated, macromolecular crowding plays a critical role in life as we know it.     

High-Melting Lipid Mixtures and the Origin of Detergent-Resistant Membranes Studied with Temperature-Solubilization Diagrams

The origin of resistance to detergent solubilization in certain membranes, or membrane components, is not clearly understood. We have studied the solubilization by Triton X-100 of binary mixtures composed of egg sphingomyelin (SM) and either ceramide, diacylglycerol, or cholesterol. Solubilization has been assayed in the 4–50°C range, and the results are summarized in a novel, to our knowledge, form of plots, that we have called temperature-solubilization diagrams. Despite using a large detergent excess (lipid/detergent 1:20 mol ratio) and extended solubilization times (24–48 h) certain mixtures were not amenable to Triton X-100 solubilization at one or more temperatures. DSC of all the lipid mixtures, and of all the lipid + detergent mixtures revealed that detergent resistance was associated with the presence of gel domains at the assay temperature. Once the system melted down, solubilization could occur. In general adding high-melting lipids limited the solubilization, whereas the addition of low-melting lipids promoted it. Lipidomic analysis of Madin-Darby canine kidney cell membranes and of the corresponding detergent-resistant fraction indicated a large enrichment of the nonsolubilized components in saturated diacylglycerol and ceramide. SM-cholesterol mixtures were special in that detergent solubilization was accompanied, for certain temperatures and compositions, by an independent phenomenon of reassembly of the partially solubilized lipid bilayers. The temperature at which lysis and reassembly prevailed was ∼25°C, thus for some SM-cholesterol mixtures solubilization occurred both above and below 25°C, but not at that temperature. These observations can be at the origin of the detergent resistance effects observed with cell membranes, and they also mean that cholesterol-containing detergent-resistant membrane remnants cannot correspond to structures existing in the native membrane before detergent addition.     

Factors Affecting Tropical Tree Damage and Survival after Catastrophic Wind Disturbance

The structure and dynamics of cyclone‐prone tropical forests are driven in part by variation in tree species resistance to and survival after wind‐induced structural damage. We determined the factors associated with tree damage and 3‐yr survival following Category 5 Cyclone Olaf on the Polynesian island of Ta'u, American Samoa. Despite sustaining a high rate of severe damage (34.6% of all trees snapped, 23.0% uprooted), system resilience was high with 74.3 percent stem survival overall and an annual mortality rate of 7.9 percent compared with 2.1 percent in nearby undisturbed late successional forest. Three‐yr survival rate of trees sustaining severe damage was 63.1 percent, compared to about 89 percent for trees sustaining only branch loss or defoliation. Three‐yr survival differed according to damage type, 78.5 percent after snapping vs. 38.4 percent after uprooting. Species differed widely in resistance to and survival after snapping and uprooting. Several species and individual traits were associated with the probability of snapping or uprooting; however, wood density was the only species trait consistently, and negatively, associated with the probability of sustaining either damage type. Survival after snapping was negatively associated with the proportion of the tree snapped off, which was determined by individual tree architecture. Species growth rate was negatively associated with survival after uprooting, indicating the importance of shade tolerance for survival after uprooting. Thus, whereas species traits seemed to exclusively underpin resistance to and survival after uprooting, they only partly accounted for snapping resistance, and did not determine the intensity of snap damage or survival after snapping. Our results highlight the importance of considering each damage type separately when considering ecological trade‐offs.     

The Bahamian Flora: Plant Exploration,Living Collections,and DNA – A Journey Started in 1963

Dr. John Popenoe was Director of Fairchild Tropical Botanic Garden (FTBG) between 1963 and 1989. Dr. Popenoe was a strong supporter of the Bahamian flora, and in 1963 he obtained extramural funds to develop a living collection focusing on Bahamian plants that was established in FTBG. During his tenure FTBG supported the publication of the latest comprehensive flora of this archipelago. A project initiated by the first FTBG herbarium curator, William Gillis, but published by Donovan and Helen Correll (with illustrations of Priscilla Fawcett) in 1982. This living collection of Bahamian plants has supplied plant material for molecular phylogenetic studies worldwide. There are DNA phylogenies for only 10 of the 89 Bahamian endemics; most of the material of these phylogenies came from plants from these collections (three species) and/or from fragments of herbarium specimens collected by Donovan Correll (six species). Only two of the species included in these phylogenies are from collections unrelated to FTBG. Excluding species restricted to the Bahamas, material from 14 Caribbean Island endemics that are part of these collections has been used in phylogenetic studies. The available molecular phylogenies show that the Bahamian endemics are closely related to species from the West Indies or continental areas of the Caribbean Basin. There is also a paucity of population genetic studies based on DNA markers focusing on Bahamian plants. Only two of the four available population genetic studies are for a Bahamian endemic taxon.     

Genetic structure of cherry fruit fly (Rhagoletis cingulata) populations across managed,unmanaged, and natural habitats

The cherry fruit fly (CFF), Rhagoletis cingulata Loew (Diptera: Tephritidae: Trypetini), is endemic to eastern North America and Mexico, where its primary native host is black cherry [Prunus serotina Ehrh. (Rosaceae)]. Cherry fruit fly is also a major economic pest of the fruit of cultivated sweet (Prunus avium L.) and tart (Prunus cerasus L.) cherries. Adult CFF that attack wild black cherry and introduced, domesticated cherries in commercial and abandoned orchards are active at different times of the summer, potentially generating allochronic isolation that could genetically differentiate native from sweet and tart CFF populations. Here, we test for host‐related genetic differences among CFF populations in Michigan attacking cherries in managed, unmanaged, and native habitats by scoring flies for 10 microsatellite loci. Little evidence for genetic differentiation was found across the three habitats or between the northern and southern Michigan CFF populations surveyed in the study. Local gene flow between native black cherry, commercial, and abandoned orchards may therefore be sufficient to overcome seasonal differences in adult CFF activity and prevent differentiation for microsatellites not directly associated with (tightly linked to) genes affecting eclosion time. The results do not support the existence of host‐associated races in CFF and imply that flies attacking native, managed, and unmanaged cherries should be considered to represent a single population for pest management purposes.