Somatic Excision of the Ac Transposable Element in Transgenic Arabidopsis thaliana after 5-Azacytidine Treatment

We have introduced the maize Ac transposable element in Arabidopsisthaliana and found that after three selfing generations, theelement is immobile and extensively methylated. Moreover, thenopaline synthase (nos) gene present on the same transferredT-DNA, was active early after transformation and regeneration,but inactive in most of the S1 progeny. We used 5-azacytidine(5AzaC) to determine whether a reduction in the methylationwould affect both Ac transposition and expression of the nosgene. After treatment with 5AzaC doses from 0.3 mM to 1.0 mM,approximately 25% of the plants produced detectable amountsof nopaline, indicating that the nos gene was reactivated. Usingthe polymerase chain reaction (PCR) to detect the empty donorsite left by Ac transposition, we demonstrated that 5AzaC alsoactivates Ac excision in the transgenic plants. Approximately13% of the 5AzaC treated plants (doses from 0.1 mM to 1.0 mM)were shown to have empty donor sites due to Ac excision. Noneof the plants cultivated in the absence of 5AzaC showed evidencefor Ac transposition or reactivation of the nos gene. Furtheranalysis using Southern blot indicate that some de-methylationocurred in the genome of individual plants. These results mayrepresent demethylation in few cells during development whichmay be sufficient to reactivate in these cells the expressionof the nos and Ac transposase transgenes, the latter promotingAc transposition in somatic cells. (Received July 16, 1996; Accepted January 8, 1997)     

Quantitative proteomic analysis of PCSK9 gain of function in human hepatic HuH7 cells

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in cholesterol homeostasis, mediating degradation of the liver low-density lipoprotein receptor (LDLR). In fact, gain- and loss-of-function PCSK9 variations in human populations associate with hyper- or hypo- cholesterolemia, respectively. Exactly how PCSK9 promotes degradation of the LDLR, the identity of the other biomolecules involved in this process, and the global effect of PCSK9 on other proteins has not been thoroughly studied. Here we employ stable isotope labeling with amino acids in cell culture (SILAC) to present the first quantitative, subcellular proteomic study of proteins affected by the stable overexpression of a gain-of-function PCSK9 membrane-bound chimera (PCSK9-V5-ACE2) in comparison to control, empty vector transfections in a human hepatocyte (HuH7) cell line. The expression level of 327 of 5790 peptides was modified by PCSK9-V5-ACE2 overexpression. Immunoblotting was carried out for the control transferrin receptor, shown to be unaffected in cells overexpressing PCSK9-V5-ACE2, thus validating our SILAC results. We also used immunoblotting to confirm the novel SILAC results of up- and down-regulation of several proteins in cells overexpressing PCSK9-V5-ACE2. Moreover, we documented the novel down-regulation of the EH domain binding protein-1 (EHBP1) in a transgenic PCSK9 mouse model and its up-regulation in a PCSK9 knockout mouse model.     

Post-Hurricane Responses of Climbers in a Tropical Mountain Rain Forest of Martinique

Hurricane Dean, a category 4 storm, impacted the forests along the western coast of Martinique on August 17, 2007. In March 2008, plots were selected in the rainforest of the Plateau Concorde, which presented a range of post-hurricane damage. The study focused on climber community patterns in two extreme ranges of disturbance (HIP: highly damaged plots; LIP: lightly damaged plots). The objectives of the study were to i) obtain data on forest architecture and light regime, ii) determine the species diversity and abundance among climbers, and iii) identify recurrent patterns of association among traits within this flora. Fisheye photos showed significant differences in canopy geometry and light microclimate between HIP and LIP. One transect in each extreme range of disturbance showed that the floors were similarly covered but the distribution of foliar density in the vertical structure was evenly distributed from the floor to the canopy in LIP and was exclusively concentrated within the first meter in HIP. Five hundred and eleven climbers were counted, measured and identified in 12 plots (30?m?×?30?m). Correspondence analysis of the selected traits revealed four functional groups (C1 to C4). C1 and C2 included understory climbers and C3 and C4 were composed of overstory climbers showing differences in stem or leaf nature. We identified eight species among the 161 trees >5?cm dbh (diameter at breast height) assessed in the 12 plots supporting climbers. A linear regression showed that large trees were more colonized than smaller trunks. The mean number of climbers per host trunk was 2.7, with no significant difference between HIP and LIP plots. In spite of the great differences in forest architecture, canopy openness and light regime, the 16 climber species were present in all plots. Five species, all belonging to one of the four functional groups, varied in abundance. In the HIP plots, the dramatic expansion of Cayaponia americana (C1), a ruderal plant frequently observed at lower altitudes, was noteworthy. Our results suggest that climbers present highly efficient morphological adaptations to hurricanes. Indeed, they are mostly linked to a single host, they strongly reiterate after breakage, and they show low clumping.     

Engineered rhizosphere: the trophic bias generated by opine-producing plants is independent of the opine type, the soil origin, and the plant species

In a previous study, we demonstrated that transgenic Lotus plants producing opines (which are small amino acid and sugar conjugates) specifically favor growth of opine-degrading rhizobacteria. The opine-induced bias was repeated and demonstrated with another soil type and another plant species (Solanum nigrum). This phenomenon is therefore independent of both soil type and plant species.     

Chronological distribution of the tiger Panthera tigris and the Asiatic lion Panthera leo persica in their common range in Asia

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PCSK9 deficiency unmasks a sex- and tissue-specific subcellular distribution of the LDL and VLDL receptors in mice

Proprotein convertase subtilisin kexin type 9 (PCSK9), the last member of the family of Proprotein Convertases related to Subtilisin and Kexin, regulates LDL-cholesterol by promoting the endosomal/lysosomal degradation of the LDL receptor (LDLR). Herein, we show that the LDLR cell surface levels dramatically increase in the liver and pancreatic islets of PCSK9 KO male but not female mice. In contrast, in KO female mice, the LDLR is more abundant at the cell surface enterocytes, as is the VLDL receptor (VLDLR) at the cell surface of adipocytes. Ovariectomy of KO female mice led to a typical KO male pattern, whereas 17β-estradiol (E2) treatment restored the female pattern without concomitant changes in LDLR adaptor protein 1 (also known as ARH), disabled-2, or inducible degrader of the LDLR expression levels. We also show that this E2-mediated regulation, which is observed only in the absence of PCSK9, is abolished upon feeding the mice a high-cholesterol diet. The latter dramatically represses PCSK9 expression and leads to high surface levels of the LDLR in the hepatocytes of all sexes and genotypes. In conclusion, the absence of PCSK9 results in a sex- and tissue-specific subcellular distribution of the LDLR and VLDLR, which is determined by E2 levels.