To explore the origins and consequences of tetraploidy in the African clawed frog, we sequenced the Xenopus laevis genome and compared it to the related diploid X. tropicalis genome. We demonstrate the allotetraploid origin of X. laevis by partitioning its genome into two homeologous subgenomes, marked by distinct families of “fossil” transposable elements. Based on the activity of these elements and the age of hundreds of unitary pseudogenes, we estimate that the two diploid progenitor species diverged ~34 million years ago (Mya) and combined to form an allotetraploid ~17–18 Mya. 56% of all genes are retained in two homeologous copies. Protein function, gene expression, and the amount of flanking conserved sequence all correlate with retention rates. The subgenomes have evolved asymmetrically, with one chromosome set more often preserving the ancestral state and the other experiencing more gene loss, deletion, rearrangement, and reduced gene expression.

Surfaces that repel both water and liquid oils completely are very useful in daily life and in industry. Although surfaces with outstanding water-repellent properties have been developed and intensively studied recently," -31 surfaces with excellent oil-repellent properties, however, have not yet been reported in spite of their crucial importance. Wettability of a solid surface with a liquid is enhanced by the surface in particular by the presence of fractal structures. When the contact angle between a liquid and a flat solid surface is larger than 90", the surface repels the liquid completely if the surface rough enough.For a fractal rough structure the relationship between the contact angle of the flat surface Q and that of the rough surface 0, is expressed by the Equation (a).[2.3. In Equation (a),( L / I ) D -2 is the surface area magnification factor, L and I are the upper and lower limits of the fractal behavior of the surface, and D the fractal dimension. This idea has been realized recently for super water-repellent surfaces having the contact angle of 174", on using fractal We have applied the same concept in this work to the completely novel, super oil-repellent surfaces. The greatest difficulty in obtaining the super oil-repellent surface is to make a flat surface that has a contact angle greater than 9 0 for oils. Here the surface tension of the solid needed to achieve this condition is estimated. The contact angle 0 on the flat surface is determined by Young's equation [Eq. (b),where y s , yl,, and ysL are the surface tensions of the solid, the liquid, and the solid/liquid interfacial tension, respectively]. When the contact angle is 90", ys must be equal to ysL. The interfacial tension ysL can be approximated by Equation (c) (c) when the interaction force between the two materials is same kind. [61 Combining Equations (b) and (c), we obtain ys = yL/4 as condition for 0 = 90".Typical surface tensions of oils are 20-30 m N m -', and the value of y s must be on the order of several mNm-'. Such a small surface tension for a solid can probably be provided only by the trifluoromethyl group.['] Accordingly, our strategy for making super oil-repellent surfaces was to obtain a surface of enough roughness and then to cover the rough surface with trifluoromethyl groups by treating it with fluorinated compounds. Figure 1 shows a scanning electron microscopic photograph of the anodically oxidized rough surface of aluminum plate. This surface was analyzed by the box counting method1233J and found to be a fractal (dimension 2.16). This untreated surface is superwettable towards liquids, but can be converted into a super r-;'sr = ;'s + 71, -2b ;'s 7,.

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In early development of Xenopus laevis, it is known that activities of polypeptide growth factors are negatively regulated by their binding proteins. In this study, follistatin, originally known as an activin-binding protein, was shown to inhibit all aspects of bone morphogenetic protein (BMP) activity in early Xenopus embryos. Furthermore, using a surface plasmon resonance biosensor, we demonstrated that follistatin can directly interact with multiple BMPs at significantly high affinities. Interestingly, follistatin was found to be noncompetitive with the BMP receptor for ligand binding and to form a trimeric complex with BMP and its receptor. The results suggest that follistatin acts as an organizer factor in early amphibian embryogenesis by inhibiting BMP activities by a different mechanism from that used by chordin and noggin.