Association between Wolbachia and Spiroplasma within Drosophila neotestacea: an emerging symbiotic mutualism?

Interspecific mutualism can evolve when specific lineages of different species tend to be associated with each other from one generation to the next. Different maternally transmitted endosymbionts occurring within the same cytoplasmic lineage fulfil this requirement. Drosophila neotestacea is infected with maternally transmitted Wolbachia and Spiroplasma, which are cotransmitted at high frequency in natural populations. Molecular phylogenetic evidence indicates that both endosymbionts have been present in D. neotestacea for considerable evolutionary periods. Thus, conditions are suitable for the evolution of mutualism between them. In support of this possibility, there is a significant positive association between Wolbachia and Spiroplasma infection in many samples of D. neotestacea from natural populations. Theoretically, such a positive association can result from either mutualism between these endosymbionts or recent spread. Collections from present‐day populations suggest that recent spread and mutualism have both operated to generate the positive association between Wolbachia and Spiroplasma. If selection acts on the combination of these two endosymbionts, they may be in the early stages of evolution of a more complex, cooperative association.     

Indirect Effects of a Keystone Herbivore Elevate Local Animal Diversity

Abstract: We quantified indirect effects of white-tailed deer (Odocoileus virginianus) on ground-dwelling herpetofauna and invertebrates in Cuyahoga Valley National Park, Ohio, USA. We placed cover boards at 12 sites, each consisting of a 10 × 10-m fenced (exclosure) plot and an unfenced (control) plot. Periodically, during May-December 2004 and May-September 2005, we counted salamanders, snakes, and a variety of invertebrate taxa. Salamander, snake, and gastropod abundance as well as invertebrate richness (no. of species or higher level taxa) were higher in control than exclosure plots. Our findings suggest that management actions taken to regulate deer densities could have the unintended effect of reducing local animal diversity.     

The effects of elevated atmospheric CO2 on the amount and depth distribution of plant water uptake in a California annual grassland

Soil moisture profiles can affect species composition and ecosystem processes, but the effects of increased concentrations of atmospheric carbon dioxide ([CO₂]) on the vertical distribution of plant water uptake have not been studied. Because plant species composition affects soil moisture profiles, and is likely to shift under elevated [CO₂], it is also important to test whether the indirect effects of [CO₂] on soil water content may depend on species composition. We examined the effects of elevated [CO₂] and species composition on soil moisture profiles in an annual grassland of California. We grew monocultures and a mixture of Avena barbata and Hemizonia congesta– the dominant species of two phenological groups – in microcosms exposed to ambient (～370 μmol mol^?1) and elevated (～700 μmol mol^?1) [CO₂]. Both species increased intrinsic and yield‐based water use efficiency under elevated [CO₂], but soil moisture increased only in communities with A. barbata, the dominant early‐season annual grass. In A. barbata monocultures, the [CO₂] treatment did not affect the depth distribution of soil water loss. In contrast to communities with A. barbata, monocultures of H. congesta, a late‐season annual forb, did not conserve water under elevated [CO₂], reflecting the increased growth of these plants. In late spring, elevated [CO₂] also increased the efficiency of deep roots in H. congesta monocultures. Under ambient [CO₂], roots below 60 cm accounted for 22% of total root biomass and were associated with 9% of total water loss, whereas in elevated [CO₂], 16% of total belowground biomass was associated with 34% of total water loss. Both soil moisture and isotope data showed that H. congesta monocultures grown under elevated [CO₂] began extracting water from deep soils 2 weeks earlier than plants in ambient [CO₂].     

Effects of Ultraviolet Radiation on Amphibians: Field Experiments

SYNOPSIS. Numerous reports suggest that populations of amphibiansfrom a wide variety of locations are experiencing populationdeclines and/or range reductions. In some cases, unusually highegg mortality has been reported. Field experiments have beenused with increasing frequency to investigate ultraviolet radiationas one of the potential factors contributing to these declines.Results from field experiments illustrate that hatching successof eggs is hampered by ultraviolet radiation in a number ofspecies, while other species appear to be unaffected. Continuedmortality in early life-history stages may ultimately contributeto a population decline. Although UV-B radiation may not contributeto the population declines of all species, it may play a rolein the population decline of some species, especially thosethat lay eggs in open shallow water subjected to solar radiationand in those that have a poor ability to repair UV-induced DNAdamage.     

Oxidation of Glucose,Ribose, Alanine,and Glutamate by Leishmania braziliensis panamensis1

The metabolism of [1-¹⁴C]- and [6-¹⁴C]glucose, [1-¹⁴]ribose, [1-¹⁴C]- and [U-¹⁴C]alanine, and [1-¹⁴C]- and [5-¹⁴C]glutamate by the promastigotes of Leishmania braziliensis panamensis was investigated in cells resuspended in Hanks' balanced salt solution supplemented with ribose, alanine, or glutamate. The ratio of ¹⁴CO₂ produced from [1-¹⁴C]glucose to that from [6-¹⁴C]glucose ranged from about two to six, indicating appreciable carbon flow through the pentose phosphate pathway. A functional pentose phosphate pathway was further demonstrated by the production of ¹⁴CO₂ from [1-¹⁴C]ribose although the rate of ribose oxidation was much lower than the rate of glucose oxidation. The rate of ¹⁴CO₂ production from [1-¹⁴C]glucose was almost linear with time of incubation, whereas that of [6-¹⁴C]glucose accelerated, consistent with an increasing rate of flux through the Embden-Meyerhof pathway during incubation. Increasing the assay temperature from 26°C to 34°C had no appreciable effect on the rates or time courses of oxidation of either [1-¹⁴C]- or [6-¹⁴C]glucose or of [1-¹⁴C]ribose. Both alanine and glutamate were oxidized by L. b. panamensis, and at rates comparable to or appreciably greater than the rate of oxidation of glucose. The ratios of ¹⁴CO₂ produced from [1-¹⁴C]- to [U-¹⁴C]alanine and from [1-¹⁴C]- to [5^-14C]glutamate indicated that these compounds were metabolized via a functioning tricarboxylic acid cycle and that most of the label that entered the tricarboxylic acid cycle was oxidized to carbon dioxide. Heating the cultures for 6 or 12 h at 34°C, which converts the promastigotes into an ellipsoidally shaped intermediate form, decreased the rates of oxidation of glucose, alanine, and glutamate. The oxidation of glutamate decreased by about 50% and 70% after a 6-h or 12-h heat treatment, respectively. Returning the heated cultures to 26°C initiated a reversion to the promastigote form and recovery of the rate of glucose oxidation, but glutamate oxidation did not return to control levels by 19 h at 26°C.     

Ourmia melon virus, a virus from Iran with novel properties

A virus associated with a mosaic disease in melons in the Ourmia district in northern Iran was mechanically transmissible to a wide range of test plants but was not transmitted using aphids, the whitefly Trialeurodes vaporariorum or the mite Tetranychus urticae. Its rather stable particles somewhat resembled those of both geminiviruses and alfalfa mosaic virus; they were 18·5 nm in mean width, parallel-sided, and of several discrete lengths, 30 nm and 37 nm being the shortest and commonest lengths. Both ends of all particles were sharply triangular in profile. The particles contained linear single-stranded RNA of three sizes, estimated as 0·91,0·35 and 0·32, all × 10⁶ molecular weight, and two coat proteins of 26·3 and 23·3 × 10³ estimated molecular weight. The virus, named Ourmia melon virus, appears to be the first described representative of a new virus group.     

Cloning and Identification of Arp1, an Actin-Related Protein from Pneumocystis carinii

ABSTRACT. The complete Pneumocystis carinii Arp1 gene has been sequenced from two cDNA clones. The gene encodes a protein 385 bp in length with an estimated size of 45,000 kD. The A + T% for the Arp1 gene and a 900-bp sequence upstream of the gene were 63.7% and 70.3%, respectively. These values are consistant with A + T codon preference displayed by P. carinii and are similar to values reported for other P. carinii genes. The predicted amino acid sequence of the P. carinii Arp1 protein had a similarity of 87.6% with Neurospora crassa Arp1, 82.1% similarity with vertebrate centractin, and 71.2% similarity with the Saccharomyces cerevisiae Act5p. Expression of Arp1 mRNA in P. carinii was detectable via synthesis of cDNA and subsequent PCR amplification. Affinity purified antibodies against S. cerevisiae Act5p, and canine centractin recognized both the recombinantly expressed protein and a 45,000 kD protein in P. carinii nuclear extracts. The Arp1 gene is the second member of the actin multigene family that has been identified in P. carinii .     

Evidence of land plant affinity for the Devonian fossil Protosalvinia (Foerstia)

The Devonian plant fossil Protosalvinia (Foerstia) has been examined by solid-state ¹³C nuclear magnetic resonance spectroscopy (NMR) and pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). Results of these studies reveal that the chemical structure of Protosalvinia is remarkably similar to that of coalified wood. A well-defined phenolic carbon peak in the NMR spectra and the appearance of phenol and alkylated phenols in pyrolysis products are clearly indicative of lignin-like compounds. These data represent significant new information on the chemical nature of Protosalvinia and provide the first substantial organic geochemical evidence for land plant affinity. ▭ Protosalvinia, Foerstia, Upper Devonian, biostratigraphy, carbon-13 NMR, PY-GC-MS, lignin.