3D spectroscopy with VLT/GIRAFFE - III: Mapping electron densities in distant galaxies

We used the moderately high spectral resolution of FLAMES/GIRAFFE (R=10000) to derive electron densities from [OII] line ratios in 6 galaxies at z~0.55. These measurements have been done through the GIRAFFE multiple integral field units and are the very first mapping of electron densities in such distant objects. This allows us to confirm an outflow and identify the role of giant HII regions in galactic disks. Such measurements could be used in the future to investigate the nature of the physical processes responsible for the high star formations rates observed in galaxies between z~0.4 and z~1.Comment: (1) GEPI, Obs. Meudon, France ;(2) MPE, Germany. See also ESO press release http://www.eso.org/outreach/press-rel/pr-2006/pr-10-06.html. To appear in A&

Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline

The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline

Tomato strigolactones are derived from carotenoids and their biosynthesis is promoted by phosphate starvation

Strigolactones are rhizosphere signalling compounds that mediate host location in arbuscular mycorrhizal (AM) fungi and parasitic plants. Here, the regulation of the biosynthesis of strigolactones is studied in tomato (Solanum lycopersicum). * Strigolactone production under phosphate starvation, in the presence of the carotenoid biosynthesis inhibitor fluridone and in the abscisic acid (ABA) mutant notabilis were assessed using a germination bioassay with seeds of Orobanche ramosa; a hyphal branching assay with Gigaspora spp; and by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis. * The root exudates of tomato cv. MoneyMaker induced O. ramosa seed germination and hyphal branching in AM fungi. Phosphate starvation markedly increased, and fluridone strongly decreased, this activity. Exudates of notabilis induced approx. 40% less germination than the wild-type. The LC-MS/MS analysis confirmed that the biological activity and changes therein were due to the presence of several strigolactones; orobanchol, solanacol and two or three didehydro-orobanchol isomers. * These results show that the AM branching factors and parasitic plant germination stimulants in tomato root exudate are strigolactones and that they are biosynthetically derived from carotenoids. The dual activity of these signalling compounds in attracting beneficial AM fungi and detrimental parasitic plants is further strengthened by environmental conditions such as phosphate availabilityWe acknowledge funding by the European Commission (Intra- European Marie Curie postdoctoral fellowship to J.A.L-R.; FP6-MEIF-CT-2005-024345) and The Netherlands Organi- zation for Scientific Research (NWO; VICI-grant to H.B., R.M. and F.V.).Peer reviewe