DEFECTIVE EMBRYO AND MERISTEMS genes are required for cell division and gamete viability in Arabidopsis

The DEFECTIVE EMBRYO AND MERISTEMS 1 (DEM1) gene encodes a protein of unknown biochemical function required for meristem formation and seedling development in tomato, but it was unclear whether DEM1’s primary role was in cell division or alternatively, in defining the identity of meristematic cells. Genome sequence analysis indicates that flowering plants possess at least two DEM genes. Arabidopsis has two DEM genes, DEM1 and DEM2, which we show are expressed in developing embryos and meristems in a punctate pattern that is typical of genes involved in cell division. Homozygous dem1 dem2 double mutants were not recovered, and plants carrying a single functional DEM1 allele and no functional copies of DEM2, i.e. DEM1/dem1 dem2/dem2 plants, exhibit normal development through to the time of flowering but during male reproductive development, chromosomes fail to align on the metaphase plate at meiosis II and result in abnormal numbers of daughter cells following meiosis. Additionally, these plants show defects in both pollen and embryo sac development, and produce defective male and female gametes. In contrast, dem1/dem1 DEM2/dem2 plants showed normal levels of fertility, indicating that DEM2 plays a more important role than DEM1 in gamete viability. The increased importance of DEM2 in gamete viability correlated with higher mRNA levels of DEM2 compared to DEM1 in most tissues examined and particularly in the vegetative shoot apex, developing siliques, pollen and sperm. We also demonstrate that gamete viability depends not only on the number of functional DEM alleles inherited following meiosis, but also on the number of functional DEM alleles in the parent plant that undergoes meiosis. Furthermore, DEM1 interacts with RAS-RELATED NUCLEAR PROTEIN 1 (RAN1) in yeast two-hybrid and pull-down binding assays, and we show that fluorescent proteins fused to DEM1 and RAN1 co-localize transiently during male meiosis and pollen development. In eukaryotes, RAN is a highly conserved GTPase that plays key roles in cell cycle progression, spindle assembly during cell division, reformation of the nuclear envelope following cell division, and nucleocytoplasmic transport. Our results demonstrate that DEM proteins play an essential role in cell division in plants, most likely through an interaction with RAN1.     

Prediction of the metabolic syndrome status based on dietary and genetic parameters, using Random Forest

Metabolic syndrome (MS) is a cluster of metabolic abnormalities associated with an increased risk of developing cardio-vascular diseases, stroke or type II diabetes. Overall, the aetiology of MS is complex and is determined by the interplay between genetic and environmental factors although it is still difficult to untangle their respective roles. The aim of this study was to determine which factors and/or combination of factors could be predictive of MS status. Using a large case–control study nested in a well-characterized cohort, we investigated genetic and dietary factors collected at entry in subjects having developed MS 7 years later. We used a classification technique called Random Forest to predict the MS status from the analysis of these data. We obtained an overall out-of-bag estimation of the correct classification rate of 71.7% (72.1% for the control subjects and 70.7% for the cases). The plasma concentration of 16.1 was the most discriminative variable, followed by plasma concentration of C18.3(n-6) and C18.2. Three SNPs were selected by Random Forest (APOB rs512535, LTA rs915654 and ACACB rs4766587). These SNPs were also significantly associated to the MS by a univariate Fisher test.     

High-frequency plant regeneration through adventitious shoot formation in castor (<Emphasis Type="Italic">Ricinus communis</Emphasis> L.)

An efficient plant regeneration protocol was established for castor (Ricinus communis L.). Hypocotyl tissue from zygotic embryo axis produced adventitious shoots when treated with either thidiazuron (TDZ, 1 μM) or 6-benzylaminopurine (BA, 20 μM). TDZ resulted in more than a threefold higher rate of shoot induction (a maximum of 24.2 shoots per explant) than BA (6.8 shoots). Our results also showed that the pretreatment of explants in the dark increased the number of shoots regenerated per explant by 82% and 36% with TDZ and BA, respectively. The elongation of hypocotyl tissue in the dark appears to be the primary cause of the increase. Comparable rates of rooting were achieved on the media supplemented with either indole-3-butyric acid (IBA, 84.3%) or 1-naphthaleneacetic acid (NAA, 87.4%) at 5 μM. However, IBA was more efficient in promoting root and shoot development, resulting in a higher rate of establishment (93.5%) in the soil, compared to the rate with NAA (39.5%). Histological analysis showed the adventitious induction of the shoot buds originated from the cortex of the hypocotyl tissue.     

Research in general practice: a survey of incentives and disincentives for research participation

Background Recruitment rates of general practitioners (GPs) to do research vary widely. This may be related to the ability of a study to incorporate incentives for GPs and minimise barriers to participation.Method A convenience sample of 30 GPs, ten each from the Sydney intervention and control groups Ageing in General Practice ‘Detection and Management of Dementia’ project (GP project) and 10 GPs who had refused participation, were recruited to determine incentives and barriers to participating in research. GPs completed the 11-item ‘Meeting the challenges of research in general practice: general practitioner questionnaire’ (GP survey) between months 15 and 24 of the GP project, and received brief qualitative interviews from a research GP to clarify responses where possible.Results The most important incentives the 30 GPs gave for participating in the project were a desire to update knowledge (endorsed by 70%), to help patients (70%), and altruism (60%). Lack of time (43%) was the main barrier. GPs also commented on excessive paperwork and an inadequate explanation of research.Conclusions While a desire to update knowledge and help patients as well as altruism were incentives, time burden was the primary barrier and was likely related to extensive paperwork. Future recruitment may be improved by minimising time burden, making studies simpler with online data entry, offering remuneration and using a GP recruiter.     

A systematic histological analysis of palm fruits VII. The Cyrtostachydinae (Arecaceae)

Fruit specimens representing five taxa of the genusCyrtostachys were examined histologically in order to characterize the pericarp anatomy of the monogeneric subtribe Cyrtostachydinae (tribe Areceae, subfamily Arecoideae), as part of an ongoing survey of the family. The pericarp in this genus can be characterized by a combination of papillate epidermis, heavy layer of tanniniferous/pigmented cells below the epidermis, a system of vascular bundles with thick fibrous sheaths with purely fibrous bundles frequently above and below, absence of brachysclereids, and a very thin sclerified locular epidermis. On the basis of pericarp structure alone, the genus might be most closely related to theGronophyllum alliance of the subtribe Arecinae. This diverges somewhat from the hypothesis of relationship with theAreca group of the Arecinae resulting from two DNA-based phylogenetic studies, and even further from the hypothesis of relationship withIguanura suggested by another DNA-based phylogenetic study.     

Potentiation of the efficacy of murine L1210 leukemia vaccine by a novel immunostimulator 7-thia-8-oxoguanosine: Increased survival after immunization with vaccine plus 7-thia-8-oxoguanosine

Summary We have investigated the ability of a novel immunopotentiator, 7-thia-8-oxoguanosine (7T8OG) to increase the efficacy of a weakly immunogenic murine L1210 leukemia vaccine. The vaccine was prepared by irradiating L1210 leukemia cells in a cesium source with a total of 6000-R dose. DBA/2 mice were treated with 150 mg/kg 7T8OG and/or with vaccine consisting of 10⁷ irradiated cells. In combination therapy, mice first received the vaccine and then were injected with 75 mg/kg 7T8OG 2 h and 4 h after vaccination. One week after the last treatment all mice were inoculated with 10⁴ live leukemia cells intraperitoneally. Control, untreated mice (n = 66) injected with 10⁴ live leukemia cells had a mean survival time ± standard error of 10.5±0.2 days. Treating mice (n = 66) with one, two or three doses of 7T8OG administered i.p. 1 week apart did not increase survival (mean survival time = 10.7 days). Mice immunized with one, two or three doses of vaccine had 14.5±1.1, 45.4±6.2 and 68.3±10.6 days mean survival, respectively. 7T8OG-stimulated vaccination increased the survival dramatically. The best survival was noted when the mice were treated with 2× (vaccine + 7T8OG). Immunization of mice (n = 30) with this treatment regimen increased the mean survival to 156±10.0 days. Over 90% of mice that were treated this way had a cumulative survival time greater than 160 days. In contrast, only 12% of the mice immunized twice with the leukemia vaccine alone survived over 160 days. These results suggest a rationale for the use of this immuno-potentiator with various vaccines for a more effective immunization.