Adenylyl Cyclase Plays a Regulatory Role in Development, Stress Resistance and Secondary Metabolism in Fusarium fujikuroi

The ascomycete fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces secondary metabolites of biotechnological interest, such as gibberellins, bikaverin, and carotenoids. Production of these metabolites is regulated by nitrogen availability and, in a specific manner, by other environmental signals, such as light in the case of the carotenoid pathway. A complex regulatory network controlling these processes is recently emerging from the alterations of metabolite production found through the mutation of different regulatory genes. Here we show the effect of the targeted mutation of the acyA gene of F. fujikuroi, coding for adenylyl cyclase. Mutants lacking the catalytic domain of the AcyA protein showed different phenotypic alterations, including reduced growth, enhanced production of unidentified red pigments, reduced production of gibberellins and partially derepressed carotenoid biosynthesis in the dark. The phenotype differs in some aspects from that of similar mutants of the close relatives F. proliferatum and F. verticillioides: contrary to what was observed in these species, ΔacyA mutants of F. fujikuroi showed enhanced sensitivity to oxidative stress (H2O2), but no change in heavy metal resistance or in the ability to colonize tomato tissue, indicating a high versatility in the regulatory roles played by cAMP in this fungal group

Geochronology and regional correlation of continental Permo-Triassic sediments in West Texas

Session: A 100 Year Quest to Graduate the Geological Column With an Accurate Time Scale II Posters: abstract V51A-2512Section: Volcanology, Geochemistry, PetrologyAlthough many aspects of marine sections spanning the Permian-Triassic boundary (PTB) have been studied in great detail across a broad paleogeographic area, less is known about the timing, pace, and extent of environmental changes and extinctions across this boundary in continental environments, particularly along the Panthalassa margin. Extensive outcrops in the Ochoan Series of west Texas provide an opportunity to investigate the terrestrial record spanning the PTB. The presence of several silicic tuffs in these sections allows for precise radioisotopic dating using both U-Pb ...link_to_OA_fulltex

"Ochoan" Quartermaster Formation of North Texas, USA, Part II: Magnetostratigraphy and geochronology

Session no. 153 - Permian-Triassic Changes and Extinction Event: New Insights from Sedimentary, Geochemical, and Paleobiological Records and Modeling Approaches I: paper no. 153-6As part of an effort to obtain a well-dated record of paleoenvironmental change (specifically in paleotemperatures and paleoatmospheric pCO2) from terrestrial strata of the latest Ochoan Series, spanning the Permian-Triassic boundary (PTB), in the southwestern United States (westernmost Pangea), we are building a detailed magnetostratigraphic record of the Ochoan Series strata represented by the Dewey Lake/Quartermaster formations (DL/QM), in west Texas. These strata are unique in that they are the only Upper Permian sedimentary rocks from western Pangea containing volcanic ash fall deposits. They offer a unique and critical paleogeographic vantage on events across the PTB, which encompassed the most severe biotic crisis known since the emergence of metazoan life on Earth and whose cause(s) remain one of the most profound unresolved questions in earth sciences. Earlier studies showed that the red-beds of the DL/QM fms are high-fidelity recorders of the paleomagnetic field and remarkably resistant to remagnetization. Dual polarity characteristic magnetizations (ChRM) are largely carried by a mix of both specular and pigment hematite, with no discernable directional difference between the carriers, as revealed by chemical demagnetization. For these red beds, hematite cement was early acquired and is an important remanence carrier. We have collected new data from ten sites over a 3 meter interval below and above the lowest ash in the DL/QM exposed at the South Prong, Caprock Canyon, and 14 sites through the part of the Country Road 207 section that exposes a probably correlative ash. Polarity data show that the DL/QM section immediately above and below these two ash occurrences is entirely normal polarity, consistent with previous work suggesting that the PTB lies within a normal polarity chron. The interval containing another ash about 20 m above the lower ash at Caprock Canyon, is of reverse polarity. Ar/Ar and U-Pb data for these ashes are consistent with this placement for the PTB, i.e. within error of the U-Pb age of 252.4 Ma for the GSSP at Meishan, China. Given that some 14 normal polarity chrons have been recognized in the latest Permian, following the termination of the Permo-Carboniferous Reverse Superchron (PCRS), we suspect that the lower DL/QM section will eventually reveal a finer polarity record.link_to_OA_fulltex

Silicon in magnetite: High resolution microanalysis of magnetite-ilmenite intergrowths

Magnetite-ilmenite “oxidation-exsolution” intergrowths from an original titanomagnetite microphenocryst from an ash flow tuff unit have been studied using conventional transmission electron microscopy and analytical electron microscopy. Silicon has been found to be in solid solution in all of the magnetite studied and in some of the coexisting ilmenite. The average value in magnetite is 1.2 wt.% Si, equivalent to solid solution of 9 mole % Fe 2 SiO 4 . Silicon is also present in very small silicate inclusions and as unusual Si-rich domains of uncertain origin in magnetite. The inclusions and domains may be irregularly distributed through the magnetite in sizes well below those resolvable with the electron microprobe. Microprobe analyses for Si in magnetite generally reflect these heterogeneities in addition to a component presumably in solid solution. The petrologic implications of the data can be assessed only when relevant thermochemical data become available and the distribution of Si in magnetite is better understood.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47334/1/410_2004_Article_BF00378006.pd