Structure and fractal dimensions of root systems of four co-occurring fruit tree species from Botswana

Coarse root systems of four different fruit tree species from southern Africa were completely excavated and semi-automatically digitized. Spatial distributions of root length were determined from the digitally-reconstructed branching systems. Furthermore, the fractal characteristic of the coarse root systems was shown by determining the box-counting dimensions. These quantitative methods revealed architectural differences between the species, probably due to different ecophysiological strategies. For fine root samples, which were taken before digging out the whole systems, fractal analysis of the planar projections showed no significant inter-species differences. Methodologically, the study underlines the usefulness of digital 3-D reconstruction in root research.Structures et dimensions fractales des systèmes racinaires provenant de quatre espèces d'arbres fruitiers de Botswana. Des systèmes de grosses racines, provenant de quatre espèces différentes d'arbres fruitiers d'Afrique du Sud, ont été complètement déterrés et digitalisés semi-automatiquement. Les distributions spatiales des longueurs de racines ont été calculées à partir des maquettes informatiques reconstituées. En outre, le caractère fractal des systèmes de grosses racines a été prouvé par une détermination de dimensions utilisant la méthode du comptage de boites. Ces méthodes quantitatives révèlent des différences architecturales entre les espèces, résultant probablement de différentes stratégies écophysiologiques. Pour les échantillons de racines fines, obtenus avant l'excavation des systèmes complets, l'analyse fractale des projections planes n'a pas montré de différences significatives entre les espèces. Concernant la méthode, l'étude fait apparaître l'apport de la reconstruction digitale 3-D dans le domaine de la recherche sur les appareils racinaires

© INRA, EDP Sciences Original article

Structure and fractal dimensions of root systems of four co-occurring fruit tree species from Botswan

Interdependence of phosphorus, nitrogen, potassium and magnesium translocation by the ectomycorrhizal fungus Paxillus involutus

Translocation is shown of phosphorus, nitrogen, potassium and magnesium to a P-deficient host from ectomycorrhizal fungal hyphae.Mycorrhizal (with Paxillus involutus) and nonmycorrhizal P-deficient spruce (P. abies) seedlings were grown in a two-compartment sand-culture system. Hyphal translocation of nutrients from the inner compartment (penetrated only by hyphae) to the host was measured using mass balance (for N, P and K) or stable isotope (N-15 and Mg-25) methods.Addition of P to the hyphal compartment strongly stimulated hyphal growth, and this also increased both seedling P status and growth. Hyphae translocated nonlimiting elements in addition to P, contributing 52, 17, 5 and 3-4%, respectively, to total P, N, K or Mg plant uptake. The potential role of the ectomycorrhizal mycelium in K acquisition was demonstrated. Translocation to mycorrhizal seedings of N, K and Mg was strongly reduced when hyphal P-fluxes ceased; this translocation of nonlimiting nutrients depended on simultaneous translocation of P.The ectomycorrhizal mycelium has an active role in P acquisition from sources not available to roots. Nutrient fluxes within fungal hyphae are interdependent and strong coupling of N, K and Mg fluxes with long-distance P translocation in the mycorrhizal mycelium occurs

Association of two genomic variants with HPV type-specific risk of cervical cancer

Problem: Human papillomavirus infection is integral to developing invasive cervical cancer in the majority of patients. In a recent genome-wide association study, rs9357152 and rs4243652 have been associated with seropositivity for HPV16 or HPV18, respectively. It is unknown whether these variants also associate with cervical cancer triggered by either HPV16 or HPV18. Methods: We investigate whether the two HPV susceptibility variants show association with type-specific cervical cancer in a genetic case-control study with cases stratified by HPV16 or HPV18, respectively. We further tested whether rs9357152 modulates gene expression of any of 36 genes at the human leukocyte antigen locus in 256 cervical tissues. Results: rs9357152 was associated with invasive HPV16-positive cervical cancer (OR 1.33, 95%CI 1.03–1.70, p = 0.03), and rs4243652 was associated with HPV18-positive adenocarcinomas (OR 2.96, 95%CI 1.18–7.41, p = 0.02). These associations remained borderline significant after testing against different sets of controls. rs9357152 was found to be an eQTL for HLA-DRB1 in HPV-positive cervical tissues (pANOVA = 0.0009), with the risk allele lowering mRNA levels. Conclusions: We find evidence that HPV seropositivity variants at chromosome 6 and 14 may modulate type-specific cervical cancer risk. rs9357152 may exert its effect through regulating HLA-DRB1 induction in the presence of HPV. In regard of multiple testing, these results need to be confirmed in larger studies

Genome-wide association study and functional follow-up identify 14q12 as a candidate risk locus for cervical cancer.

Cervical cancer is among the leading causes of cancer-related death in females worldwide. Infection by human papillomavirus (HPV) is an established risk factor for cancer development. However, genetic factors contributing to disease risk remain largely unknown. We report on a genome-wide association study (GWAS) on 375 German cervical cancer patients and 866 healthy controls, followed by a replication study comprising 658 patients with invasive cervical cancer, 1361 with cervical dysplasia and 841 healthy controls. Functional validation was performed for the top GWAS variant on chromosome 14q12 (rs225902, close to PRKD1). After bioinformatic annotation and in silico predictions, we performed transcript analysis in a cervical tissue series of 317 samples and demonstrate rs225902 as an expression quantitative trait locus (eQTL) for FOXG1 and two tightly co-regulated long non-coding RNAs at this genomic region, CTD-2251F13 (lnc-PRKD1-1) and CTD-2503I6 (lnc-FOXG1-6). We also show allele-specific effects of the 14q12 variants via luciferase assays. We propose a combined effect of genotype, HPV status and gene expression at this locus on cervical cancer progression. Taken together, this work uncovers a potential candidate locus with regulatory functions and contributes to the understanding of genetic susceptibility to cervical cancer