Browsing by Subject "nucleus"

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Complete Sequences of Organelle Genomes from the Medicinal Plant Rhazya Stricta (Apocynaceae) and Contrasting Patterns of Mitochondrial Genome Evolution Across Asterids
(2014-05) Park, Seongjun; Ruhlman, Tracey A.; Sabir, Jamal S. M.; Mutwakil, Mohammed H. Z.; Baeshen, Mohammed N.; Sabir, Meshaal J.; Baeshen, Nabih A.; Jansen, Robert K.; Park, Seongjun; Ruhlman, Tracey A.; Jansen, Robert K.
Rhazya stricta is native to arid regions in South Asia and the Middle East and is used extensively in folk medicine to treat a wide range of diseases. In addition to generating genomic resources for this medicinally important plant, analyses of the complete plastid and mitochondrial genomes and a nuclear transcriptome from Rhazya provide insights into inter-compartmental transfers between genomes and the patterns of evolution among eight asterid mitochondrial genomes. Results: The 154,841 bp plastid genome is highly conserved with gene content and order identical to the ancestral organization of angiosperms. The 548,608 bp mitochondrial genome exhibits a number of phenomena including the presence of recombinogenic repeats that generate a multipartite organization, transferred DNA from the plastid and nuclear genomes, and bidirectional DNA transfers between the mitochondrion and the nucleus. The mitochondrial genes sdh3 and rps14 have been transferred to the nucleus and have acquired targeting presequences. In the case of rps14, two copies are present in the nucleus; only one has a mitochondrial targeting presequence and may be functional. Phylogenetic analyses of both nuclear and mitochondrial copies of rps14 across angiosperms suggests Rhazya has experienced a single transfer of this gene to the nucleus, followed by a duplication event. Furthermore, the phylogenetic distribution of gene losses and the high level of sequence divergence in targeting presequences suggest multiple, independent transfers of both sdh3 and rps14 across asterids. Comparative analyses of mitochondrial genomes of eight sequenced asterids indicates a complicated evolutionary history in this large angiosperm clade with considerable diversity in genome organization and size, repeat, gene and intron content, and amount of foreign DNA from the plastid and nuclear genomes. Conclusions: Organelle genomes of Rhazya stricta provide valuable information for improving the understanding of mitochondrial genome evolution among angiosperms. The genomic data have enabled a rigorous examination of the gene transfer events. Rhazya is unique among the eight sequenced asterids in the types of events that have shaped the evolution of its mitochondrial genome. Furthermore, the organelle genomes of R. stricta provide valuable genomic resources for utilizing this important medicinal plant in biotechnology applications.
EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
(2011-06) Meech, K. J.; A'Hearn, M. F.; Adams, J. A.; Bacci, P.; Bai, J.; Barrera, L.; Battelino, M.; Bauer, J. M.; Becklin, E.; Bhatt, B.; Biver, N.; Bockelee-Morvan, D.; Bodewits, D.; Bohnhardt, H.; Boissier, J.; Bonev, B. P.; Borghini, W.; Brucato, J. R.; Bryssinck, E.; Buie, M. W.; Canovas, H.; Castellano, D.; Charnley, S. B.; Chen, W. P.; Chiang, P.; Choi, Y. J.; Christian, D. J.; Chuang, Y. L.; Cochran, Anita L.; Colom, P.; Combi, M. R.; Coulson, I. M.; Crovisier, J.; Dello Russo, N.; Dennerl, K.; DeWahl, K.; DiSanti, M. A.; Facchini, M.; Farnham, T. L.; Fernandez, Y.; Floren, H. G.; Frisk, U.; Fujiyoshi, T.; Furusho, R.; Fuse, T.; Galli, G.; Garcia-Hernandez, D. A.; Gersch, A.; Getu, Z.; Gibb, E. L.; Gillon, M.; Guido, E.; Guillermo, R. A.; Hadamcik, E.; Hainaut, O.; Hammel, H. B.; Harker, D. E.; Harmon, J. K.; Harris, W. M.; Hartogh, P.; Hashimoto, M.; Hausler, B.; Herter, T.; Hjalmarson, A.; Holland, S. T.; Honda, M.; Hosseini, S.; Howell, E. S.; Howes, N.; Hsieh, H. H.; Hsiao, H. Y.; Hutsemekers, D.; Immler, S. M.; Jackson, W. M.; Jeffers, S. V.; Jehin, E.; Jones, T. J.; Ovelar, M. D.; Kaluna, H. M.; Karlsson, T.; Kawakita, H.; Keane, J. V.; Keller, L. D.; Kelley, M. S.; Kinoshita, D.; Kiselev, N. N.; Kleyna, J.; Knight, M. M.; Kobayashi, H.; Kobulnicky, H. A.; Kolokolova, L.; Kreiny, M.; Kuan, Y. J.; Kuppers, M.; Lacruz, J. M.; Landsman, W. B.; Lara, L. M.; Lecacheux, A.; Levasseur-Regourd, A. C.; Li, B.; Licandro, J.; Ligustri, R.; Lin, Z. Y.; Lippi, M.; Lis, D. C.; Lisse, C. M.; Lovell, A. J.; Lowry, S. C.; Lu, H.; Lundin, S.; Magee-Sauer, K.; Magain, P.; Manfroid, J.; Epifani, E. M.; McKay, A.; Melita, M. D.; Mikuz, H.; Milam, S. N.; Milani, G.; Min, M.; Moreno, R.; Mueller, B. E. A.; Mumma, M. J.; Nicolini, M.; Nolan, M. C.; Nordh, H. L.; Nowajewski, P. B.; Team, O.; Ootsubo, T.; Paganini, L.; Perrella, C.; Pittichova, J.; Prosperi, E.; Radeva, Y. L.; Reach, W. T.; Remijan, A. J.; Rengel, M.; Riesen, T. E.; Rodenhuis, M.; Rodriguez, D. P.; Russell, R. W.; Sahu, D. K.; Samarasinha, N. H.; Caso, A. S.; Sandqvist, A.; Sarid, G.; Sato, M.; Schleicher, D. G.; Schwieterman, E. W.; Sen, A. K.; Shenoy, D.; Shi, J. C.; Shinnaka, Y.; Skvarc, J.; Snodgrass, C.; Sitko, M. L.; Sonnett, S.; Sosseini, S.; Sostero, G.; Sugita, S.; Swinyard, B. M.; Szutowicz, S.; Takato, N.; Tanga, P.; Taylor, P. A.; Tozzi, G. P.; Trabatti, R.; Trigo-Rodriguez, J. M.; Tubiana, C.; de Val-Borro, M.; Vacca, W.; Vandenbussche, B.; Vaubaillion, J.; Velichko, F. P.; Velichko, S. F.; Vervack, R. J.; Vidal-Nunez, M. J.; Villanueva, G. L.; Vinante, C.; Vincent, J. B.; Wang, M.; Wasserman, L. H.; Watanabe, J.; Weaver, H. A.; Weissman, P. R.; Wolk, S.; Wooden, D. H.; Woodward, C. E.; Yamaguchi, M.; Yamashita, T.; Yanamandra-Fischer, P. A.; Yang, B.; Yao, J. S.; Yeomans, D. K.; Zenn, T.; Zhao, H.; Ziffer, J. E.; Cochran, Anita L.
Earth- and space-based observations provide synergistic inFormation for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was similar to 16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.
Frozen To Death? Detection Of Comet Hale-Bopp At 30.7 AU (Research Note)
(2011-07) Szabo, G. M.; Sarneczky, K.; Kiss, L. L.; Szabo, G. M.
Context. Comet Hale-Bopp 9C/1995 O1) has been the most interesting comet ever encountered by modern astronomy, which continued to display significant activity at a solar distance of 25.7 AU. It is unclear when and how this activity will finally cease. Aims. We present new observations with the ESO 2.2 m telescope at La Silla to monitor the activity of Hale-Bopp at 30.7 AU solar distance. Methods. On 2010-12-04, 26 CCD images were taken with 180 s exposure times for photometry and morphology. Results. The comet was detected in R and had a total brightness of 23(m).3 +/- 0(m).2, which corresponds to an absolute brightness of R(1, 1, 0) = 8(m).3. The profile of the coma was star-like at a seeing of 1 ''.9, without any evidence of a coma or tail extending farther than 2 ''.5 (= 55 000 km in projection) and exceeding 26.5 mag/arcs(2) surface brightness. The measured total brightness corresponds to a relative total reflecting surface, a(R)C, of 485 km(2), nine times less than three years before. The calculated a(R)C value would imply a nucleus with 60-65 km radius assuming 4% albedo. This size estimate contradicts significantly the previous results scattering around 35 km. Conclusions. We propose that the comet may still be in a low level of activity, despite the lack of a prominent coma. Alternatively, if the nucleus is already dormant, the albedo should be as high as 13%, assuming a radius of 35 km. With this observation, Hale-Bopp has become the most distant comet ever observed, far beyond the orbit of Neptune.
Nuclear Star-Forming Ring of the Milky Way: Simulations
(2011-07) Kim, Sungsoo S.; Saitoh, Takayuki R.; Jeon, Myouungwon; Figer, Donald F.; Merritt, David; Wada, Keiichi; Jeon, Myouungwon
We present hydrodynamic simulations of gas clouds in the central kpc region of the Milky Way that is modeled with a three-dimensional bar potential. Our simulations consider realistic gas cooling and heating, star Formation, and supernova feedback. A ring of dense gas clouds forms as a result of X-1-X-2 orbit transfer, and our potential model results in a ring radius of similar to 200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star Formation rate (SFR) in the CMZ, similar to 2 x 10(7) M-circle dot and similar to 0.1 M-circle dot yr(-1). Star Formation in our simulations takes place mostly in the outermost X-2 orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-forming rings seen in some external disk galaxies. Furthermore, from the relatively small size of the Milky Way's nuclear bulge, which is thought to be a result of sustained star Formation in the CMZ, we infer that the Galactic inner bulge probably had a shallower density profile or stronger bar elongation in the past.
The Spatial Distribution Of C-2, C-3, And NH In Comet 2P/Encke
(2013-12) Dorman, Garrett; Pierce, Donna M.; Cochran, Anita L.; Cochran, Anita L.
We examine the spatial distribution of C-2, C-3, and NH radicals in the coma of comet Encke in order to understand their abundances and distributions in the coma. The observations were obtained from 2003 October 22-24, using the 2.7 m telescope at McDonald Observatory. Building on our original study of CN and OH, we have used our modified version of the vectorial model, which treats the coma as one large cone, in order to reproduce Encke's highly aspherical and asymmetric coma. Our results suggest that NH can be explained by the photodissociation of NH2, assuming that NH2 is produced rapidly from NH3 in the innermost coma. Our modeling of C-2 and C-3 suggests a multi-generational photodissociation process may be required for their production. Using the results of our previous study, we also obtain abundance ratios with respect to OH and CN. Overall, we find that Encke exhibits typical carbon-chain abundances, and the results are consistent with other studies of comet Encke.