The outer halos of elliptical galaxies

Recent progress is summarized on the determination of the density distributions of stars and dark matter, stellar kinematics, and stellar population properties, in the extended, low surface brightness halo regions of elliptical galaxies. With integral field absorption spectroscopy and with planetary nebulae as tracers, velocity dispersion and rotation profiles have been followed to ~4 and ~5-8 effective radii, respectively, and in M87 to the outer edge at ~150 kpc. The results are generally consistent with the known dichotomy of elliptical galaxy types, but some galaxies show more complex rotation profiles in their halos and there is a higher incidence of misalignments, indicating triaxiality. Dynamical models have shown a range of slopes for the total mass profiles, and that the inner dark matter densities in ellipticals are higher than in spiral galaxies, indicating earlier assembly redshifts. Analysis of the hot X-ray emitting gas in X-ray bright ellipticals and comparison with dynamical mass determinations indicates that non-thermal components to the pressure may be important in the inner ~10 kpc, and that the properties of these systems are closely related to their group environments. First results on the outer halo stellar population properties do not yet give a clear picture. In the halo of one bright galaxy, lower [alpha/Fe] abundances indicate longer star formation histories pointing towards late accretion of the halo. This is consistent with independent evidence for on-going accretion, and suggests a connection to the observed size evolution of elliptical galaxies with redshift.Comment: 8 pages. Invited review to appear in the proceedings of "Galaxies and their Masks" eds. Block, D.L., Freeman, K.C. & Puerari, I., 2010, Springer (New York

Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity

Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var. cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4). All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3 also accepts a wide range of substrates but with very strong preference for producing benzyl acetate. Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating 268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the multiplicity of AAT genes accounts for the great diversity of esters formed in melon

Identification of refugia and post-glacial colonisation routes of European white oaks based on chloroplast DNA and fossil pollen evidence

The geographic distribution throughout Europe of each of 32 chloroplast DNA variants belonging to eight white oak species sampled from 2613 populations is presented. Clear-cut geographic patterns were revealed by the survey. These distributions, together with the available palynological information, were used to infer colonisation routes out of the glacial period refugia. In western Europe in particular, movements out of the Iberian and the Italian Peninsulas can be clearly identified. Separate refugia are also present in eastern Balkans, whereas further west in this peninsula similarities with Italy were evident. Movements resulting in the exchange of haplotypes between refugia both during the present interglacial and probably also during earlier glacial cycles were therefore inferred. The consequences of these past exchanges is that phylogenetically divergent haplotypes have sometimes followed very similar colonisation routes, limiting somewhat the phylogeographic structure. Cases of geographic disjunction in the present-day distribution of haplotypes are also apparent and could have been induced by the existence of rapid climatic changes at the end of the glacial period (specifically the Younger Dryas cold period), which resulted in range restriction following an early warm period during which oak first expanded from its primary refugia. This cold phase was followed by a new period of expansion at the outset of the Holocene, involving in some cases ‘secondary’ refugia. It is expected that these short climate oscillations would have led to a partial reshuffling of haplotype distribution. Early association between haplotypes and oak species are also suggested by the data, although extensive introgression among species has ultimately largely blurred the pattern. This implies that colonisation routes may have been initially constrained by the ecological characteristics of the species hosting each chloroplast variant. We suggest for instance that two oak species distributed in the north of the Iberian Peninsula (Quercus petraea and Q. pubescens) are recent post-glacial immigrants there. When considered together, conclusions on the location of glacial period refugia and the colonisation routes derived from molecular information and fossil pollen data appear to be both largely compatible and complementary.Rémy J. Petit; Simon Brewer; Sándor Bordács; Kornel Burg; Rachid Cheddadi; Els Coart; Joan Cottrell; Ulrike M. Csaikl; Barbara van Dam; John D. Deans; Santiago Espinel; Silvia Fineschi; Reiner Finkeldey; Izabela Glaz; Pablo G. Goicoechea; Jan Svejgaard Jensen; Armin O. König; Andrew J. Lowe; Søren Flemming Madsen; Gabor Mátyás; Robert C. Munro; Flaviu Popescu; Danko Slade; Helen Tabbener; Sven G. M. de Vries; Birgit Ziegenhagen; Jacques-Louis de Beaulieu and Antoine Kremerhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503310/description#descriptio