Identification of the Arabidopsis thaliana flavonoid 3'-hydroxylase gene and functional expression of the encoded P450 enzyme

Schoenbohm C, Martens S, Eder C, Forkmann G, Weisshaar B. Identification of the Arabidopsis thaliana flavonoid 3'-hydroxylase gene and functional expression of the encoded P450 enzyme. Biological Chemistry. 2000;381(8):749-753.The phenylpropanoid pathway results in the synthesis of thousands of compounds, including flavonoids like flavonols, anthocyanidins and tannins. In Arabidopsis thaliana, the lack of tannins in the seed coat (testa) causes the transparent testa (tt) phenotype. In the present study, we identified the gene responsible for the tt7 mutation. We show that TT7 encodes the enzyme flavonoid 3'-hydroxylase (F3'H), and demonstrate that this P450-dependent monooxygenase has F3'H activity. The availability of the AtF3'H gene and promoter sequence will allow us to study the coregulation of a complete set of flavonol and anthocyanidin biosynthesis genes in A. thaliana, and makes in vitro synthesis of hydroxylated flavonoids more feasible

New kinematic and geochronologic evidence for the Quaternary evolution of the Central Anatolian fault zone (CAFZ)

As the kinematics of active faults that bound the Anatolian plate are well studied, it is now essential to improve our understanding of the style and rates of intraplate deformation to constrain regional strain partitioning and improve seismic risk assessments. One of these internal structures, the Central Anatolian fault zone (CAFZ), was originally defined as a regionally significant left-lateral "tectonic escape" structure, stretching for 700km in a NE direction across the Anatolian plate. We provide new structural, geomorphic, and geochronologic data for several key segments within the central part of the CAFZ that suggest that the sinistral motion has been overstated. The Ecemis fault, the southernmost part of the CAFZ, has a late-Quaternary minimum slip rate of 1.1 +/- 0.4mm a(-1), slower than originally proposed. Farther north, the Erciyes fault has fed a linear array of monogenetic vents of the Erciyes stratovolcano and Ar-40/Ar-39 dating shows a syneruptive stress field of ESE-WNW extension from 580 +/- 130 ka to 210 +/- 180 ka. In the Erciyes basin, and central part of the CAFZ, we mapped and recharacterized the Erkilet and Gesi faults as predominantly extensional. These long-term geological rates support recent GPS observations that reveal ESE-WNW extension, which we propose as the driver of faulting since 2.73 +/- 0.08Ma. The slip rates and kinematics derived in this study are not typical of an "escape tectonic" structure. The CAFZ is a transtensional fault system that reactivates paleotectonic structures and accommodates E-W extension associated with the westward movement of Anatolia

Uplift histories from river profiles

Longitudinal river profiles, where elevation of a river bed is plotted as a function of distance along the river bed, contain information about uplift rate. When a region adjacent to a reference level (e.g., sea level) is uplifted, a rapid change in gradient occurs near the river mouth. The erosional process causes this change in gradient to migrate upstream. Thus a river profile is effectively a 'tape recording' of the uplift rate history, provided that the erosional process can be adequately parameterized. Here, we use a non-linear equation to relate the shape of a river profile, z(x), to uplift rate history, U(t). If erosion is assumed to be dominated by knickpoint retreat, an inverse model can be formulated and used to calculate uplift rate histories. Our model builds upon standard stream profile analysis, which focuses on the relationship between profile slope and drainage area. We have applied this analytical approach to river profiles from the Bié Dome, Angola. Calculated uplift rate histories agree with independent geologic estimates

Direct measurement of strain rates in ductile shear zones: A new method based on syntectonic dikes

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