The genome sequence of the protostome Daphnia pulex encodes respective orthologues of a neurotrophin, a Trk and a p75NTR: Evolution of neurotrophin signaling components and related proteins in the bilateria

Background

Neurotrophins and their Trk and p75NTR receptors play an important role in the nervous system. To date, neurotrophins, Trk and p75NTR have only been found concomitantly in deuterostomes. In protostomes, homologues to either neurotrophin, Trk or p75NTR are reported but their phylogenetic relationship to deuterostome neurotrophin signaling components is unclear. Drosophila has neurotrophin homologues called Spätzles (Spz), some of which were recently renamed neurotrophins, but direct proof that these are deuterostome neurotrophin orthologues is lacking. Trks belong to the receptor tyrosine kinase (RTK) family and among RTKs, Trks and RORs are closest related. Flies lack Trks but have ROR and ROR-related proteins called NRKs playing a neurotrophic role. Mollusks have so far the most similar proteins to Trks (Lymnaea Trk and Aplysia Trkl) but the exact phylogenetic relationship of mollusk Trks to each other and to vertebrate Trks is unknown. p75NTR belongs to the tumor necrosis factor receptor (TNFR) superfamily. The divergence of the TNFR families in vertebrates has been suggested to parallel the emergence of the adaptive immune system. Only one TNFR representative, the Drosophila Wengen, has been found in protostomes. To clarify the evolution of neurotrophin signaling components in bilateria, this work analyzes the genome of the crustacean Daphnia pulex as well as new genetic data from protostomes.

Results

The Daphnia genome encodes a neurotrophin, p75NTR and Trk orthologue together with Trkl, ROR, and NRK-RTKs. Drosophila Spz1, 2, 3, 5, 6 orthologues as well as two new groups of Spz proteins (Spz7 and 8) are also found in the Daphnia genome. Searching genbank and the genomes of Capitella, Helobdella and Lottia reveals neurotrophin signaling components in other protostomes.

Conclusion

It appears that a neurotrophin, Trk and p75NTR existed at the protostome/deuterostome split. In protostomes, a "neurotrophin superfamily" includes Spzs and neurotrophins which respectively form two paralogous families. Trks and Trkl proteins also form closely related paralogous families within the protostomian RTKs, whereby Trkls are absent in deuterostomes. The finding of p75NTR in several protostomes suggests that death domain TNFR superfamily proteins appeared early in evolution.     

Enhancement of artemisinin concentration and yield in response to optimization of nitrogen and potassium supply to Artemisia annua

Background and Aims

The resurgence of malaria, particularly in the developing world, is considerable and exacerbated by the development of single-gene multi-drug resistances to chemicals such as chloroquinone. Drug therapies, as recommended by the World Health Organization, now include the use of antimalarial compounds derived from Artemisia annua – in particular, the use of artemisinin-based ingredients. Despite our limited knowledge of its mode of action or biosynthesis there is a need to secure a supply and enhance yields of artemisinin. The present study aims to determine how plant biomass can be enhanced while maximizing artemisinin concentration by understanding the plant''s nutritional requirements for nitrogen and potassium.

Methods

Experiments were carried out, the first with differing concentrations of nitrogen, at 6, 31, 56, 106, 206 or 306 mg L⁻¹ being applied, while the other differing in potassium concentration (51, 153 or 301 mg L⁻¹). Nutrients were supplied in irrigation water to plants in pots and after a growth period biomass production and leaf artemisinin concentration were measured. These data were used to determine optimal nutrient requirements for artemisinin yield.

Key Results

Nitrogen nutrition enhanced plant nitrogen concentration and biomass production successively up to 106 mg N L⁻¹ for biomass and 206 mg N L⁻¹ for leaf nitrogen; further increases in nitrogen had no influence. Artemisinin concentration in dried leaf material, measured by HPLC mass spectroscopy, was maximal at a nitrogen application of 106 mg L⁻¹, but declined at higher concentrations. Increasing potassium application from 51 to 153 mg L⁻¹ increased total plant biomass, but not at higher applications. Potassium application enhanced leaf potassium concentration, but there was no effect on leaf artemisinin concentration or leaf artemisinin yield.

Conclusions

Artemisinin concentration declined beyond an optimal point with increasing plant nitrogen concentration. Maximization of artemisinin yield (amount per plant) requires optimization of plant biomass via control of nitrogen nutrition.Key words: Artemisia, fertigation, malaria, nitrogen, nutrition, potassium     

Bestimmung von Fumonisinen in komplexen Lebensmittelmatrices mittels Accelerated Solvent Extraktion (ASE)

Accelerated solvent extraction (ASE) is an alternative sample extraction procedure for fumonisins in corn and corn products. ASE gave results comparable to that of a draft CEN method, but required less extraction time. Furthermore, ASE gave significantly higher quantitative values than another method reported for extraction of fumonisins (Trucksess et al., 1995).     

Plant genetics affects arthropod community richness and composition: evidence from a synthetic eucalypt hybrid population

To examine how genetic variation in a plant population affects arthropod community richness and composition, we quantified the arthropod communities on a synthetic population of Eucalyptus amygdalina, E. risdonii, and their F1 and advanced-generation hybrids. Five major patterns emerged. First, the pure species and hybrid populations supported significantly different communities. Second, species richness was significantly greatest on hybrids (F1 > F2 > E. amygdalina > E. risdonii). These results are similar to those from a wild population of the same species and represent the first case in which both synthetic and wild population studies confirm a genetic component to community structure. Hybrids also acted as centers of biodiversity by accumulating both the common and specialist taxa of both parental species (100% in the wild and 80% in the synthetic population). Third, species richness was significantly greater on F1s than the single F2 family, suggesting that the increased insect abundance on hybrids may not be caused by the breakup of coadapted gene complexes. Fourth, specialist arthropod taxa were most likely to show a dominance response to F1 hybrids, whereas generalist taxa exhibited a susceptible response. Fifth, in an analysis of 31 leaf terpenoids that are thought to play a role in plant defense, hybrids were generally intermediate to the parental chemotypes. Within the single F2 family, we found significant associations between the communities of individual trees and five individual oil components, including oil yield, demonstrating that there is a genetic effect on plant defensive chemistry that, in turn, may affect community structure. These studies argue that hybridization has important community-level consequences and that the genetic variation present in hybrid zones can be used to explore the genetic-based mechanisms that structure communities.     

Patient and Staff Perceptions of Intradialytic Exercise before and after Implementation: A Qualitative Study

Introduction

Despite guidance and evidence for the beneficial effects of intradialytic exercise (IDE), such programmes are rarely adopted within practice and little is known about how they may best be sustained. The Theoretical Domains Framework (TDF) was used to guide the understanding of the barriers and facilitators to initial and ongoing IDE participation and to understand how these are influential at each stage.

Materials and Methods

Focus groups explored patient (n=24) and staff (n=9) perceptions of IDE prior to the introduction of a programme and, six months later, face to face semi-structured interviews captured exercising patients (n=11) and staffs’ (n=8) actual experiences. Data were collected at private and NHS haemodialysis units within the UK. All data were audio-recorded, translated where necessary, transcribed verbatim and subject to framework analysis.

Results

IDE initiation can be facilitated by addressing the pre-existing beliefs about IDE through the influence of peers (for patients) and training (for staff). Participation was sustained through the observation of positive outcomes and through social influences such as teamwork and collaboration. Despite this, environment and resource limitations remained the greatest barrier perceived by both groups.

Conclusions

Novel methods of staff training and patient education should enhance engagement. Programmes that clearly highlight the benefits of IDE should be more successful in the longer term. The barrier of staff workload needs to be addressed through specific guidance that includes recommendations on staffing levels, roles, training and skill mix.     

Insect damage in Eucalyptus: A review of plantations in Chile

Chile has more than 330 000 ha of eucalypt plantations, predominantly in the eighth to the tenth region (approximately 34 to 41°S). Eucalyptus globulus ssp. globulus is the principal eucalypt planted, but Eucalyptus nitens, Eucalyptus camaldulensis, Eucalyptus delegatensis and Eucalyptus viminalis are also grown. There are four main insect pests that have been detected attacking these eucalypts in Chile: the defoliator Gonipterus scutellatus, the bark borers Phoracantha semipunctata and Phoracantha recurva and the native wood borer Chilecomadia valdiviana. More recently, Thyrinteina arnobia and Ctenarytaina eucalypti have been detected. Gonipterus scutellatus and P. recurva have been discovered in Chile within the last 2 years and it is hoped they may still be eliminated using a combination of biological control and chemical control of local populations. Phoracantha recurva and P. semipunctata are not considered a problem because attack only occurs in areas of water deficit, away from current eucalypt plantations. Chilecomadia valdiviana can damage plantations of E. nitens but rarely attacks other eucalypts.?Chilecomadia valdiviana may cause future problems through further host shifts. Thyrinteina arnobia has only been detected during quarantine surveillance in the port of Valparaiso. Ctenarytaina eucalypti, recently detected in August 1999, had an initial limited distribution in the first region. However, since then, this insect has expanded its distribution south up to the tenth region. None of the insects recorded on eucalypts in Chile to date currently presents a threat to the eucalypt industry. It is also essential that additional resources are made available for their continued monitoring and control, particularly given that the 44% of plantations are held by small to medium property owners that would otherwise be unable to control a serious outbreak because of economic restrictions.