Fusarium ananatum sp. nov. in the Gibberella fujikuroi species complex from pineapples with fruit rot in South Africa

Pineapple (Ananas comosus) is native to South America and widely planted as a fruit crop in the tropics and sub-tropics. This plant is susceptible to a number of fungal diseases of which the most severe is fusariosis. The disease is caused by Fusarium guttiforme and occurs only in South and Central America. The occurrence of a similar disease on pineapples in South Africa has prompted a re-evaluation of the Fusarium sp. associated with pineapple fruit rot. Phylogenetic relationships of isolates from pineapples collected in Brazil and South Africa were assessed based on sequence data for the translation elongation factor-1-α, histone H3 and β-tubulin gene regions. Analyses showed that the South African isolates represent a species distinct from Brazilian isolates. The South African isolates are characterised by a concentration of aerial mycelium at the centres of the colonies, different to the Brazilian isolates that have an even distribution of aerial mycelium. Both phylogenetic and morphological data show that the disease on pineapple in South Africa is caused by a new Fusarium species described here as F. ananatum sp. nov.     

The initial step in human immunodeficiency virus type 1 GagProPol processing can be regulated by reversible oxidation

Background

Maturation of human immunodeficiency virus type 1 (HIV-1) occurs upon activation of HIV-1 protease embedded within GagProPol precursors and cleavage of Gag and GagProPol polyproteins. Although reversible oxidation can regulate mature protease activity as well as retrovirus maturation, it is possible that the effects of oxidation on viral maturation are mediated in whole, or part, through effects on the initial intramolecular cleavage event of GagProPol. In order assess the effect of reversible oxidation on this event, we developed a system to isolate the first step in protease activation involving GagProPol.

Methodology/Principal Findings

To determine if oxidation influences this step, we created a GagProPol plasmid construct (pGPfs-1C) that encoded mutations at all cleavage sites except p2/NC, the initial cleavage site in GagProPol. pGPfs-1C was used in an in vitro translation assay to observe the behavior of this initial step without interference from subsequent processing events. Diamide, a sulfhydral oxidizing agent, inhibited processing at p2/NC by >60% for pGPfs-1C and was readily reversed with the reductant, dithiothreitol. The ability to regulate processing by reversible oxidation was lost when the cysteines of the embedded protease were mutated to alanine. Unlike mature protease, which requires only oxidation of cys95 for inhibition, both cysteines of the embedded protease contributed to this inhibition.

Conclusions/Significance

We developed a system that can be used to study the first step in the cascade of HIV-1 GagProPol processing and show that reversible oxidation of cysteines of HIV-1 protease embedded in GagProPol can block this initial GagProPol autoprocessing. This type of regulation may be broadly applied to the majority of retroviruses.     

Novel associations between ophiostomatoid fungi,insects and tree hosts: current status—future prospects

Associations between fungal tree pathogens and insects have been recognized for at least 100 years. An important group of these fungi, termed ‘ophiostomatoid fungi’ on account of their morphological similarity, are represented by genera in the families Ceratocystidaceae and Ophiostomataceae. Associations between these fungi, tree-colonizing insects, and host trees have been actively researched since their first discovery. Human activities have led to the global movement of fungi from both families, resulting in the establishment of new and sometimes damaging associations between these fungi, insects and trees. Recent ‘black swan’ events have resulted in an unprecedented increase of ambrosia and bark beetle-associated diseases of forest and fruit trees. We revisit some of the most important emergent diseases caused by the ophiostomatoid fungi, outline the reasons behind the emergence of these diseases, and consider long-term prospects regarding the threats that they pose to forestry and agriculture.     

Influence of proximity to a geographical range limit on the physiology of a tropical bird

1. Species' geographical ranges can be limited by a variety of biotic and abiotic factors. Physiological challenge in response to unsuitable environmental conditions can establish limits to geographical ranges. 2. We studied the physiology of Song Wrens (Cyphorhinus phaeocephalus) across their geographical range on the isthmus of Panama, an area characterized by a strong rainfall gradient. Wrens are common on the Caribbean slope of the isthmus where annual rainfall is greatest, but wren abundance declines towards the south as annual rainfall declines. Song Wrens are completely absent from the driest third of the isthmus. 3. We searched for the existence of a physiologically induced distribution limit by measuring body condition (an integrative measure of energy balance), hematocrit (% packed red blood cells in a given blood sample), and corticosterone levels (CORT, a steroid hormone that regulates the availability of energy and the endocrine stress response) in males and females. We caught birds by luring them into nets when they responded to playback of conspecific song. 4. Wrens living in drier habitat near the geographical range edge were significantly more likely to have abnormally low hematocrit scores. Baseline CORT levels were negatively associated with rainfall in one of our three best-fit path models, indicating potential energetic challenge in some individuals. Maximum CORT levels during a 60-min period of restraint correlated significantly only with sex, being higher in females. Birds with the poorest body condition lived at the dry end of the gradient. Birds on the wet end of the gradient responded fastest to conspecific song. 5. Environmental conditions vary across geographical ranges and may influence the physiological conditions of organisms, thereby enforcing limits to species' distributions. Highly specialized species, such as birds of the rain forest understory, may be especially susceptible to environmental variation associated with changing climatic conditions.     

Anthropogenic effects on interaction outcomes: examples from insect-microbial symbioses in forest and savanna ecosystems

The influence of humans on ecosystem dynamics has been, and continues to be, profound. Anthropogenic effects are expected to amplify as human populations continue to increase. Concern over these effects has given rise to a large number of studies focusing on impacts of human activities on individual species or on biotic community structure and composition. Lacking are studies on interactions, particularly mutualisms. Because of the role of mutualisms in ecosystem stability, such studies are critically needed if we are to begin to better understand and predict the responses of ecosystems to anthropogenic change. Most organisms are involved in at least one mutualism, and many in several. Mutualisms facilitate the ability of partners to exploit particular habitats and resources, and play a large role in determining ecological boundaries. When change disrupts, enhances, or introduces new organisms into a mutualism, the outcome and stability of the original partnership(s) is altered as are effects of the symbiosis on the community and ecosystem as a whole. In this paper, using examples from six microbe-insect mutualisms in forest and savanna settings, we showcase how varied and complex the responses of mutualisms can be to an equally varied set of anthropogenic influences. We also show how alterations of mutualisms may ramify throughout affected systems. We stress that researchers must be cognizant that many observed changes in the behaviors, abundances, and distributions of organisms due to human activities are likely to be mediated by mutualists which may alter predictions and actual outcomes in significant ways.     

New records of the Cryphonectriaceae from southern Africa including Latruncellus aurorae gen. sp. nov

The Cryphonectriaceae accommodates some of the world's most important tree pathogens, including four genera known from native and introduced Myrtales in Africa. Surveys in the past 3 y in southern Africa have led to the discovery of cankers with fruiting structures resembling those of the Cryphonectriaceae on trees in the Myrtales in Namibia, South Africa, Swaziland and Zambia. These fungi were identified with morphological characteristics and DNA sequence data. For the first time we report Chrysoporthe austroafricana from Namibia and on Syzygium guineense and Holocryphia eucalypti in Swaziland on a Eucalyptus grandis clone. The host and geographic ranges of Celoporthe dispersa are expanded to include S. legatti in South Africa and S. guineense in Zambia. In addition a monotypic genus, Latruncellus aurorae gen. sp. nov., is described from Galpinia transvaalica (Lythraceae, Myrtales) in Swaziland. The present and other recent studies clearly emphasize the limited understanding of the diversity and distribution of fungi in the Cryphonectriaceae in Africa.     

Defining Catastrophic Costs and Comparing Their Importance for Adverse Tuberculosis Outcome with Multi-Drug Resistance: A Prospective Cohort Study,Peru

Background

Even when tuberculosis (TB) treatment is free, hidden costs incurred by patients and their households (TB-affected households) may worsen poverty and health. Extreme TB-associated costs have been termed “catastrophic” but are poorly defined. We studied TB-affected households'' hidden costs and their association with adverse TB outcome to create a clinically relevant definition of catastrophic costs.

Methods and Findings

From 26 October 2002 to 30 November 2009, TB patients (n = 876, 11% with multi-drug-resistant [MDR] TB) and healthy controls (n = 487) were recruited to a prospective cohort study in shantytowns in Lima, Peru. Patients were interviewed prior to and every 2–4 wk throughout treatment, recording direct (household expenses) and indirect (lost income) TB-related costs. Costs were expressed as a proportion of the household''s annual income. In poorer households, costs were lower but constituted a higher proportion of the household''s annual income: 27% (95% CI = 20%–43%) in the least-poor houses versus 48% (95% CI = 36%–50%) in the poorest. Adverse TB outcome was defined as death, treatment abandonment or treatment failure during therapy, or recurrence within 2 y. 23% (166/725) of patients with a defined treatment outcome had an adverse outcome. Total costs ≥20% of household annual income was defined as catastrophic because this threshold was most strongly associated with adverse TB outcome. Catastrophic costs were incurred by 345 households (39%). Having MDR TB was associated with a higher likelihood of incurring catastrophic costs (54% [95% CI = 43%–61%] versus 38% [95% CI = 34%–41%], p<0.003). Adverse outcome was independently associated with MDR TB (odds ratio [OR] = 8.4 [95% CI = 4.7–15], p<0.001), previous TB (OR = 2.1 [95% CI = 1.3–3.5], p = 0.005), days too unwell to work pre-treatment (OR = 1.01 [95% CI = 1.00–1.01], p = 0.02), and catastrophic costs (OR = 1.7 [95% CI = 1.1–2.6], p = 0.01). The adjusted population attributable fraction of adverse outcomes explained by catastrophic costs was 18% (95% CI = 6.9%–28%), similar to that of MDR TB (20% [95% CI = 14%–25%]). Sensitivity analyses demonstrated that existing catastrophic costs thresholds (≥10% or ≥15% of household annual income) were not associated with adverse outcome in our setting. Study limitations included not measuring certain “dis-saving” variables (including selling household items) and gathering only 6 mo of costs-specific follow-up data for MDR TB patients.

Conclusions

Despite free TB care, having TB disease was expensive for impoverished TB patients in Peru. Incurring higher relative costs was associated with adverse TB outcome. The population attributable fraction indicated that catastrophic costs and MDR TB were associated with similar proportions of adverse outcomes. Thus TB is a socioeconomic as well as infectious problem, and TB control interventions should address both the economic and clinical aspects of this disease. Please see later in the article for the Editors'' Summary     

Development of polymorphic microsatellite markers for the genetic characterisation of Knoxdaviesia proteae (Ascomycota: Microascales) using ISSR-PCR and pyrosequencing

Knoxdaviesia proteae is one of the first native ophiostomatoid fungi discovered in South Africa, where it consistently occurs in the infructescences of the iconic Cape Biome plant, Protea repens. Although numerous studies have been undertaken to better understand the ecology of K. proteae, many questions remain to be answered, particularly given its unique niche and association with arthropods for dispersal. We describe the development and distribution of microsatellite markers in K. proteae through Interspersed Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) enrichment and pyrosequencing. A large proportion of the 31492 sequences obtained from sequencing the enriched genomic DNA were characterised by microsatellites consisting of short tandem repeats and di- and tri-nucleotide motifs. Seventeen percent of these microsatellites contained flanking regions sufficient for primer design. Twenty-three primer pairs were tested, of which 12 amplified and 10 generated polymorphic fragments in K. proteae. Half of these could be transferred to the sister species, K. capensis. The developed markers will be used to investigate the reproductive system, genetic diversity and dispersal strategies of K. proteae.     

Botryosphaeriaceae species overlap on four unrelated,native South African hosts

Botryosphaeriaceae represents an important and diverse family of latent fungal pathogens of woody plants. We address the question of host range of these fungi by sampling leaves and branches of four native South African trees, including Acacia karroo (Fabaceae), Celtis africana (Cannabaceae), Searsia lancea (Anacardiaceae), and Gymnosporia buxifolia (Celastraceae). Two new species of the Botryosphaeriaceae, namely Tiarosporella africana sp. nov. and Aplosporella javeedii sp. nov. were identified, together with five known species, including Neofusicoccum parvum, Neofusicoccum kwambonambiense, Spencermartinsia viticola, Diplodia pseudoseriata, and Botryosphaeria dothidea. Most Botryosphaeriaceae occurred on more than one host. With the exception of S. lancea, which was infected by A. javeedii all the hosts were infected by more than one Botryosphaeriaceae species. Collectively, the results suggest that some intrinsic host factors, possibly combined with local environmental conditions, affect the distribution and co-infectivity of various hosts by the Botryosphaeriaceae. This would counteract the general ability of a species in the Botryosphaeriaceae to infect a broad range of plants. The combination of host and environmental factors might also explain why some Botryosphaeriaceae with apparently broad host ranges, are found on different suites of hosts in different areas of the world.     

Panmixia defines the genetic diversity of a unique arthropod‐dispersed fungus specific to Protea flowers

Knoxdaviesia proteae, a fungus specific to the floral structures of the iconic Cape Floral Kingdom plant, Protea repens, is dispersed by mites phoretic on beetles that pollinate these flowers. Although the vectors of K. proteae have been identified, little is known regarding its patterns of distribution. Seed bearing infructescences of P. repens were sampled from current and previous flowering seasons, from which K. proteae individuals were isolated and cultured. The genotypes of K. proteae isolates were determined using 12 microsatellite markers specific to this species. Genetic diversity indices showed a high level of similarity between K. proteae isolates from the two different infructescence age classes. The heterozygosity of the population was high (0.74 ± 0.04), and exceptional genotypic diversity was encountered (Ĝ = 97.87%). Population differentiation was negligible, owing to the numerous migrants between the infructescence age classes (N_m = 47.83) and between P. repens trees (N_m = 2.96). Parsimony analysis revealed interconnected genotypes, indicative of recombination and homoplasies, and the index of linkage disequilibrium confirmed that outcrossing is prevalent in K. proteae ( = 0.0067; P = 0.132). The high diversity and panmixia in this population is likely a result of regular gene flow and an outcrossing reproductive strategy. The lack of genetic cohesion between individuals from a single P. repens tree suggests that K. proteae dispersal does not primarily occur over short distances via mites as hypothesized, but rather that long-distance dispersal by beetles plays an important part in the biology of these intriguing fungi.