Miami University

About: Miami University is a education organization based out in Oxford, Ohio, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 9949 authors who have published 19598 publications receiving 568410 citations. The organization is also known as: Miami of Ohio & Miami-Ohio.

Compilation of mRNA polyadenylation signals in Arabidopsis revealed a new signal element and potential secondary structures.

Abstract: Using a novel program, SignalSleuth, and a database containing authenticated polyadenylation [poly(A)] sites, we analyzed the composition of mRNA poly(A) signals in Arabidopsis (Arabidopsis thaliana), and reevaluated previously described cis-elements within the 3'-untranslated (UTR) regions, including near upstream elements and far upstream elements. As predicted, there are absences of high-consensus signal patterns. The AAUAAA signal topped the near upstream elements patterns and was found within the predicted location to only approximately 10% of 3'-UTRs. More importantly, we identified a new set, named cleavage elements, of poly(A) signals flanking both sides of the cleavage site. These cis-elements were not previously revealed by conventional mutagenesis and are contemplated as a cluster of signals for cleavage site recognition. Moreover, a single-nucleotide profile scan on the 3'-UTR regions unveiled a distinct arrangement of alternate stretches of U and A nucleotides, which led to a prediction of the formation of secondary structures. Using an RNA secondary structure prediction program, mFold, we identified three main types of secondary structures on the sequences analyzed. Surprisingly, these observed secondary structures were all interrupted in previously constructed mutations in these regions. These results will enable us to revise the current model of plant poly(A) signals and to develop tools to predict 3'-ends for gene annotation.

The Arabidopsis SYN1 cohesin protein is required for sister chromatid arm cohesion and homologous chromosome pairing.

Abstract: The faithful transmission of chromosomes during mitosis and meiosis requires the establishment and subsequent release of cohesion between replicated chromosomes. Sister chromatid cohesion is mediated, in large part, by the cohesin complex, which consists of four highly conserved proteins: SMC1, SMC3, SCC1/REC8 and SCC3. Mitotic cohesin complexes contain SSC1, whereas meiotic cohesin complexes contain the related REC8 protein. As part of studies to identify and characterize proteins required for meiosis in plants, we previously identified a putative Arabidopsis REC8 homolog, referred to as syn1 . Preliminary cytological studies indicated that syn1 plants exhibit defects in meiotic chromosome cohesion and condensation that result in fragmentation of the chromosomes and the formation of polyads. In the experiments presented here we show that SYN1 encodes a protein that localizes to arms of meiotic chromosomes from approximately meiotic interphase to anaphase I. The protein is not detected at the centromeres or after metaphase I. Furthermore, fluorescence in situ hybridization experiments on microsporocytes from syn1 plants demonstrate that the mutation eliminates arm cohesion as early as interphase, whereas centromere cohesion is maintained until approximately anaphase I. These results indicate that although the main role of SYN1 is in chromosome arm cohesion, it is also important for maintaining cohesion at the centromeres during late stages of meiosis I.

Geochemical and temporal evolution of Cenozoic magmatism in western Turkey: Mantle response to collision, slab break-off, and lithospheric tearing in an orogenic belt

Abstract: Post-collisional magmatism in western Anatolia began in the Eocene, and has occurred in discrete pulses throughout the Cenozoic as it propagated from north to south, producing volcano- plutonic associations with varying chemical compositions. This apparent SW migration of magma- tism and accompanying extension through time was a result of the thermally induced collapse of the western Anatolian orogenic belt, which formed during the collision of the Sakarya and Tauride-Anatolide continental blocks in the late Paleocene. The thermal input and melt sources for this prolonged magmatism were provided first by slab break-off-generated aesthenospheric flow, then by lithospheric delamination-related aesthenospheric flow, followed by tectonic extension-driven upward aesthenospheric flow. The first magmatic episode is represented by Eocene granitoid plutons and their extrusive carapace that are linearly distributed along the Izmir- Ankara suture zone south of the Marmara Sea. These suites show moderately evolved com- positions enriched in incompatible elements similar to subduction zone-influenced subalkaline magmas. Widespread Oligo-Miocene volcanic and plutonic rocks with medium- to high-K calc- alkaline compositions represent the next magmatic episode. Partial melting and assimilation- fractional crystallization of enriched subcontinental lithospheric mantle-derived magmas were important processes in the genesis and evolution of the parental magmas, which experienced decreasing subduction influence and increasing crustal contamination during the evolution of the Eocene and Oligo-Miocene volcano-plutonic rocks. Collision-induced lithospheric slab break-off provided an influx of aesthenospheric heat and melts that resulted in partial melting of the previously subduction-metasomatized mantle lithosphere beneath the suture zone, producing the Eocene and Oligo-Miocene igneous suites. The following magmatic phase during the middle Miocene (16- 14 Ma) developed mildly alkaline bimodal volcanic rocks that show a decreasing amount of crustal contamination and subduction influence in time. Both melting of a subduc- tion-modified lithospheric mantle and aesthenospheric mantle-derived melt contribution played a significant role in the generation of the magmas of these rocks. This magmatic episode was attended by region-wide extension that led to the formation of metamorphic core complexes and graben systems. Aesthenospheric upwelling caused by partial delamination of the lithospheric root beneath the western Anatolian orogenic belt was likely responsible for the melt evolution of these mildly alkaline volcanics. Lithospheric delamination may have been caused by 'peeling off' during slab rollback. The last major phase of magmatism in the region, starting c.12 Ma, is represented by late Miocene to Quaternary alkaline to super-alkaline volcanic rocks that show OIB-like geochemical features with progressively more potassic compositions increasing toward south in time. These rocks are spatially associated with major extensional fault systems that acted as natural conduits for the transport of uncontaminated alkaline magmas to the surface. The melt source for this magmatic phase carried little or no subduction component and was pro- duced by the decompressional melting of aesthenospheric mantle, which flowed in beneath the atte- nuated continental lithosphere in the Aegean extensional province. This time-progressive evolution of Cenozoic magmatism and extension in western Anatolia has been strongly controlled by the interplay between regional plate-tectonic events and the mantle dynamics, and provides a realistic template for post-collisional magmatism and crustal extension in many orogenic belts.