Evolution of MicroRNA Biogenesis Genes in the Sterlet (Acipenser ruthenus) and Other Polyploid Vertebrates

MicroRNAs play a crucial role in eukaryotic gene regulation. For a long time, only little was known about microRNA-based gene regulatory mechanisms in polyploid animal genomes due to difficulties of polyploid genome assembly. However, in recent years, several polyploid genomes of fish, amphibian, and even invertebrate species have been sequenced and assembled. Here we investigated several key microRNA-associated genes in the recently sequenced sterlet (Acipenser ruthenus) genome, whose lineage has undergone a whole genome duplication around 180 MYA. We show that two paralogs of drosha, dgcr8, xpo1, and xpo5 as well as most ago genes have been retained after the acipenserid-specific whole genome duplication, while ago1 and ago3 genes have lost one paralog. While most diploid vertebrates possess only a single copy of dicer1, we strikingly found four paralogs of this gene in the sterlet genome, derived from a tandem segmental duplication that occurred prior to the last whole genome duplication. ago1,3,4 and exportins1,5 look to be prone to additional segment duplications producing up to four-five paralog copies in ray-finned fishes. We demonstrate for the first time exon microsatellite amplification in the acipenserid drosha2 gene, resulting in a highly variable protein product, which may indicate sub- or neofunctionalization. Paralogous copies of most microRNA metabolism genes exhibit different expression profiles in various tissues and remain functional despite the rediploidization process. Subfunctionalization of microRNA processing gene paralogs may be beneficial for different pathways of microRNA metabolism. Genetic variability of microRNA processing genes may represent a substrate for natural selection, and, by increasing genetic plasticity, could facilitate adaptations to changing environments.     

Characteristics of quazi-likelihood estimation of the image area in the presence of spatial noise

Asymptotic expressions for the characteristics of quasi-likelihood estimation of image area have been obtained by using the local Markov approximation method. It was shown that the accuracy of area estimation is determined by the magnitude of intensity jump over the boundary limiting the area occupied by image.     

The efficiency of detecting an object moving in the unknown direction with unknown intensities of its image and background

The maximum likelihood algorithm for detecting a space-extended object moving in the unknown direction has been synthesized and analyzed under conditions of a priori uncertainty with respect to intensities of its image and applicative background. The impact of a priori unknown intensities of the object image and the background on the detection characteristics was also investigated.     

A system of units for physical quantities involved in electromagnetics: an alternative to the International System of Units

The drawbacks of the International System of Units are analyzed and a system of units that is better justified and more suitable for teaching and research in the field of electricity and electromagnetics is proposed.     

Quazi-likelihood estimation of motion parameters during the target probing with a sequence of optical pulses

Characteristics of quasi-likelihood estimates of the target range, velocity, and acceleration have been obtained during the probing with a sequence of optical pulses. The losses in accuracy of quasi-likelihood estimates as compared with the accuracy of maximum likelihood estimates were also found.     

PbBi2Ti2.5W0.5O12: A new layered perovskite-like oxide

The PbBi₃Ti_2.5W_0.5O₁₂ oxide with a tetragonal layered perovskite-like structure (a = 3.8391 å,c = 33.421 å) was prepared by solid-state reaction followed by hot pressing. The dielectric permittivity of the ceramic was determined to be 300 at room temperature and 550 atT _c = 523 K.     

Detection and velocity estimation for an inhomogeneous spatially extended object by its image

Synthesis and analysis of maximum likelihood algorithms of detection and estimation of the velocity of the image of an inhomogeneous spatially extended object for an applicative model of useful image-background interaction are performed. The algorithm performance and the limits of applicability of the found asymptotic expressions for detection and estimation characteristics are determined using statistical computer simulation.     

Hydrodynamic characteristics and efficiency of contact elements of wet-gas-cleaning equipment

Mathematical modeling, with the use of unidimensional equations, is employed as a basis for determining the relations between the hydrodynamic characteristics and the efficiency of wet-gas-cleaning in single-pass contact elements.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 5, pp. 733–737, November, 1985.