Use of freeze-cracking in ontogenetic research in <Emphasis Type="Italic">Macrostomum lignano</Emphasis> (Macrostomida,Rhabditophora)

A method for studying whole mount flatworm embryos based on freeze-cracking of the eggs is described. This method allows successful immunohistological and immunocytological studies of whole mount embryos. It does not require the use of sharpened needles or a microinjection system to puncture the eggshell. Moreover, this method is more practical and less time-consuming than classical puncturing and much cheaper than the use of a microinjection system. The advantages of this method are illustrated by results of several immunolocalisation experiments in the macrostomid flatworm Macrostomum lignano. The optimal procedure and crucial steps for this method are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The influence of anionic lipids on SHIP2 phosphatidylinositol 3,4,5-trisphosphate 5-phosphatase activity

The SH2 domain containing inositol 5-phosphatase 2 (SHIP2) catalyzes the dephosphorylation of phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P₃) to phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P₂) and participates in the insulin signalling pathway in vivo. In a comparative study of SHIP2 and the phosphatase and tensin homologue deleted on chromosome 10 (PTEN), we found that their lipid phosphatase activity was influenced by the presence of vesicles of phosphatidylserine (PtdSer). SHIP2 PtdIns(3,4,5)P₃ 5-phosphatase activity was greatly stimulated in the presence of vesicles of PtdSer. This effect appears to be specific for di-C8 and di-C16 fatty acids of PtdIns(3,4,5)P₃ as substrate. It was not observed with inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P₄) another in vitro substrate of SHIP2, nor with Type I Ins(1,4,5)P₃/Ins(1,3,4,5)P₄ 5-phosphatase activity, an enzyme which acts on soluble inositol phosphates. Vesicles of phosphatidylcholine (PtdCho) stimulated only twofold PtdIns(3,4,5)P₃ 5-phosphatase activity of SHIP2. Both a minimal catalytic construct and the full length SHIP2 were sensitive to the stimulation by PtdSer. In contrast, PtdIns(3,4,5)P₃ 5-phosphatase activity of the Skeletal muscle and Kidney enriched Inositol Phosphatase (SKIP), another member of the mammaliam Type II phosphoinositide 5-phosphatases, was not sensitive to PtdSer. Our enzymatic data establish a specificity in the control of SHIP2 lipid phosphatase activity with PtdIns(3,4,5)P₃ as substrate which is depending on the fatty acid composition of the substrate.     

Italian weedy rice—A case of de‐domestication?

Weedy rice is a representative of the extensive group of feral weeds that derive from crops, but has returned to the lifestyle of a wild species. These weeds develop either from a hybridization of crops with wild relatives (exoferality), or by mutation of crops to weedy forms (endoferality). Due to the close relation of weed and crop, the methods for weed‐targeted containment are limited to date. A deeper understanding of the development of such weeds might help to design more efficient and sustainable approaches for weed management. Weedy rice poses a serious threat to rice yields worldwide. It is widely accepted that weedy rice has originated independently in different regions all over the world. However, details of its evolution have remained elusive. In the current study, we investigated the history of weedy rice in northern Italy, the most important rice‐growing area in Europe. Our approach was to analyze genes related to weedy traits (SD1, sh4, Rc) in weedy rice accessions compared to cultivars, and to integrate these results with phenotypic and physiological data, as well as historical information about rice farming in Italy. We arrive at a working model for the timeline of evolution of weedy rice in Italy indicating that both exoferality and endoferality acted as forces driving the development of the diverse weedy rice populations found in the region today. Models of weed evolution can help to predict the direction which weed development might take and to develop new, sustainable methods to control feral weeds.     

Linkage Maps of Lowland and Upland Tetraploid Switchgrass Ecotypes

Switchgrass (Panicum virgatum L.) is a native perennial warm season (C₄) grass that has been identified as a promising species for bioenergy research and production. Consequently, biomass yield and feedstock quality improvements are high priorities for switchgrass research. The objective of this study was to develop a switchgrass genetic linkage map using a full-sib pseudo-testcross mapping population derived from a cross between two heterozygous genotypes selected from the lowland cultivar ‘Alamo’ (AP13) and the upland cultivar ‘Summer’ (VS16). The female parent (AP13) map consists of 515 loci in 18 linkage groups (LGs) and spans 1,733 cM. The male parent (VS16) map arranges 363 loci in 17 LGs and spans 1,508 cM. No obvious cause for the lack of one LG in VS16 could be identified. Comparative analyses between the AP13 and VS16 maps showed that the two major ecotypic classes of switchgrass have highly colinear maps with similar recombination rates, suggesting that chromosomal exchange between the two ecotypes should be able to occur freely. The AP13 and VS16 maps are also highly similar with respect to marker orders and recombination levels to previously published switchgrass maps. The genetic maps will be used to identify quantitative trait loci associated with biomass and quality traits. The AP13 genotype was used for the whole genome-sequencing project and the map will thus also provide a tool for the anchoring of the switchgrass genome assembly.     

Disentangling the effects of global climate and regional land-use change on the current and future distribution of mangroves in South Africa

The mangrove distribution in South Africa is fragmented and restricted to small forest patches occupying only 16 % of the estuaries within the current range. In this study we used species distribution models to test (1) whether the absence of mangrove forest and its species (Avicennia marina, Bruguiera gymnorrhiza and Rhizophora mucronata) within their current range is driven by climate or by climate combined with human or geomorphic perturbation and (2) how climate change may potentially affect the latitudinal limit of the mangrove forests and its species in South Africa. We used three modelling techniques (generalized linear models, generalized additive models and gradient boosting machines) and a set of three climate-based predictive variables (minimum air temperature of the coldest month, waterbalance and growing-degree days) combined separately with an index of human or geomorphic perturbation. Climate variables for the future projections were derived from two general circulation models driven by two socio-economic scenarios (A2a and B2a). Within the range of the mangrove forest, the fragmented distribution of the mangroves in South Africa was not explained by our set of climate variables alone. The index of human perturbations slightly improved the predictions but the index of geomorphic perturbation did not. Climate change will create climatically suitable sites for the mangrove forest and the two species A. marina and B. gymnorrhiza beyond their current limits, but model outcomes did not agree on the future potential distribution of R. mucronata. We were able to successfully predict range limits and to detect future climatically suitable sites beyond the current limits. Factors controlling mangrove distribution within its range are still to be identified although absences were partly explained by human perturbations.     

Determinants of Change in Children’s Sedentary Time

Background

Understanding the determinants of sedentary time during childhood contributes to the development of effective intervention programmes.

Purpose

To examine family and home-environmental determinants of 1-year change in objectively measured sedentary time after-school and at the weekend.

Methods

Participants wore accelerometers at baseline and 1 year later. Longitudinal data for after-school and weekend analyses were available for 854 (41.5%male, mean±SD age 10.2±0.3years) and 718 (41.8%male, age 10.2±0.3years) participants. Information on 26 candidate determinants, including socioeconomic status (SES), availability of electronic media and parental rules for sedentary behaviours was self-reported by children or their parents at baseline. Change in the proportion of registered time spent sedentary was used as the outcome variable in multi-level linear regression models, adjusted for age, sex, body mass index and baseline sedentary time. Simple and multiple models were run and interactions with sex explored.

Results

Children from higher socioeconomic status families exhibited greater increases in after-school (beta; 95% CI for change in % time spent sedentary 1.02; 0.37, 1.66) and weekend (1.42; 0.65, 2.18) sedentary time. Smaller increases in after-school sedentary time were observed in children with more siblings (−1.00; −1.69, −0.30), greater availability of electronic media (−0.81; −1.29, −0.33) and, for boys, more frequent family visits to the park (−1.89; −3.28, −0.51) and family participation in sport (−1.28; −2.54, −0.02). Greater maternal weekend screen-time (0.45; 0.08, 0.83) and, in girls, greater parental restriction on playing outside (0.91; 0.08, 1.74) were associated with larger increases in weekend sedentary time. The analytical sample was younger, more likely to be female, had lower BMI and was of higher SES than the original baseline sample.

Conclusions

Intervention strategies aimed at reducing parents’ weekend screen-time, increasing family participation in sports or recreation (boys) and promoting freedom to play outside (girls) may contribute towards preventing the age-related increase in sedentary time.