On the Theory of Speciation Induced by Transposable Elements

A simple methematical model describes the invasion of panmictic, sexually reproducing populations by a newly introduced transposon. The model places important constraints on the properties that transposons must have to successfully invade a population and describes the kinetics with which such an invasion will occur. Invasibility conditions serve as a basis for new, detailed scenarios whereby transposon-mediated depression in fitness produces reproductive isolation of populations. These scenarios, in turn, lead to several speculations concerning the role of transposons in evolution.     

Tau-induced traffic jams reflect organelles accumulation at points of microtubule polar mismatching

It is currently accepted that tau overexpression leads to impaired organelle transport and thus to neuronal degeneration. Nevertheless, the underlying mechanisms that lead to impaired organelle transport are not entirely clear. Using cultured Aplysia neurons and online confocal imaging of human tau, microtubules (MTs), the plus-end tracking protein – end-binding protein 3, retrogradely and anterogradely transported organelles, we found that overexpression of tau generates the hallmarks of human tau pathogenesis. Nevertheless, in contrast to earlier reports, we found that the tau-induced impairment of organelle transport is because of polar reorientation of the MTs along the axon or their displacement to submembrane domains. 'Traffic jams' reflect the accumulation of organelles at points of MT polar discontinuations or polar mismatching rather than because of MT depolymerization. Our findings offer a new mechanistic explanation for earlier observations, which established that tau overexpression leads to impaired retrograde and anterograde organelle transport, while the MT skeleton appeared intact.     

Glucose Metabolism and Retention of Glucose Metabolites in the Wheat Embryo during Early Germination

There is a lag period in the growth of excised wheat (Triticum vulgare Host.) embryos extending from 0.5 hour to 4.5 hours of their imbibition in water. During this time there is a sharp increase in the embryos' capability to retain several amino and organic acids, to synthesize cell wall components and starch, and to take up glucose. Their capability to metabolize glucose also increases by 30%. Elevation of the ATP content of 1-hour embryos by incubation in 3 mm adenosine is not sufficient to bring about these changes. These changes may be a part of a metabolic adjustment in the embryos which increases their growth potential.