Genetic variation in parthenogenetic Caucasian rock lizards of the genus Lacerta (L. dahli, L. armeniaca, L. unisexualis) analyzed by DNA fingerprinting

Multilocus DNA fingerprinting has been used to study the variability of some mini- and microsatellite sequences in parthenogenetic species of Caucasian rock lizards of the genus Lacerta (L. dahli, L. armeniaca and L. unisexualis). We demonstrate that these clonally reproducing lizards possess species-specific DNA fingerprints with a low degree of intra- and interpopulation variation. Mean indices of similarity obtained using M13 DNA, (GACA)4 and (TCC)50 as probes were 0.962 and 0.966 in L. dahli and L. armeniaca, respectively. The mean index of similarity obtained using M 13 and GATA probes in L. unisexualis was estimated to be 0.95. However, despite the high degree of band-sharing, variable DNA fragments were revealed in all populations with the microsatellite probes. An particularly high level of variability was observed for (TCC)n microsatellites in populations of L. unisexualis. In fact TCC-derived DNA fingerprints were close to being individual-specific, with a mean index of similarity of 0.824. Fingerprint analysis of parthenogenetic families of L. armeniaca showed that all maternal fragments were inherited together by the progeny, and no differences in fingerprint patterns were observed. On the other hand, while identical DNA fingerprints were obtained from L. unisexualis families with M13 and (GATA)4 probes, use of the (TCC)50 probe revealed remarkable intrafamily variation in this species. It is assumed that the genetic heterogeneity observed in parthenogenetic populations may be explained, at least in part, by the existence of genetically unstable microsatellite loci. Our data serve to illustrate processes of spontaneous mutagenesis and the initial stages of clonal differentiation in natural populations of the lizard species studied.     

Revealing of allelic polymorphism in the populations of parthenogenetic lizards <Emphasis Type="Italic">Darevskia dahli</Emphasis> (Lacertidae) using locus-specific PCR

Locus-specific PCR was used to study the genetic polymorphism in three populations of parthenogenetic lizard species Darevskia dahli. The analysis was carried at the two (GATA) _n -containing loci (Du215 and Du281) using the sample of 26 individuals. A total of eight Du215 and three Du281 allelic variants were detected. It was demonstrated that all the lizards examined were heterozygous at these loci. In 12 animals, unusual Du215 allelic variant was revealed, the origin of which was thought to be associated with different types of genomic rearrangements, or segmental duplication. The populations studied were substantially different relative to the levels of allelic polymorphism, which could be explained by different habitation conditions, leading to accumulation of mutations in noncoding genome regions.     

Finding of Bov-B LINE retroelement in parthenogenetic and bisexual lizard species of the genus Darevskia (Lacertidae)

The Bov-B LINE retrotransposon was first discovered in Ruminantia and was long considered to be specific for this order. Later, this mobile element was described in snakes and some lizard species. Analysis of phylogenetic relationships of Bov-B LINE elements from different ruminants, snakes, and lizard species led to the suggestion on horizontal transfer of this retrotransposon from Squamata to Ruminantia. In the Squamata group, Bov-B LINE element was found in all snakes and some lizard species examined. The element was not detected in the genomes of some species of the genera Lacerta and Podarcis. In the present study, using PCR amplification and sequencing of PCR products, Bov-B LINE element was identified in the genomes of parthenogenetic and bisexual species of the genus Darevskia (Lacertidae), as well as in such species as Lacerta agilis and Zootoca vivipara, where this retrotransposon had not been not detected before.     

Responses of Neurons of the Extrastriate Area 21b of the Cat Brain Cortex to Changes in Orientation of Moving Visual Stimuli

We studied the responses of neurons of the extrastriate cortical area 21b of the cat to changes in orientation of the movements of visual stimuli within the receptive field (RF) of the neuron under study. Our experiments demonstrated that 24 of 108 cells (22%) responded differentially to a certain extent to orientation of the movements of visual stimuli. As a whole, neurons of the area 21b did not demonstrate fine tuning on the optimum angle of orientation. In many cases, neuronal responses to different orientations of the movement of visual stimulus depended significantly on specific parameters of this stimulus (its shape, dimensions, and contrast). Some directionally sensitive neurons responded to a change in orientation of the movement of visual stimuli by modification of the index of directionality. We also studied spatial organization of the RF of neurons with the presentation of stationary visual stimuli. Comparison of the neuronal responses to a change in orientation of the movements of stimuli and to presentation of stationary stimuli showed that the correlation between the orientation sensitivity of the neuron under study and the stationary functional organization of its RF was insignificant. We hypothesize that inhibitory processes and subthreshold influences from a space surrounding the RF play a special role in the formation of the neuronal responses generated in the associative visual cortical regions to visual stimulation.     

Peculiarities of Visually Sensitive Neurons of the Extrastriate Associative Area 21b of the Cat Brain Cortex

On cats with pretrigeminal brainstem transection, we studied the properties of visually sensitive neurons of the extrastriate associative cortical area 21b. The dimensions and spatial distribution of the receptive fields (RF) of the neurons within the vision field were determined. It was found that large-sized RF prevailed within the area 21b (10 to 200 deg², 61%; greater than 200 deg², 22%), whereas small-sized RF (1 to 10 deg²) constituted 17% of all the studied RF. Stationary visual stimuli evoked on–off, off, and on responses in 43, 30, and 27% neurons of the area 21b, respectively. In the cases where moving stimuli were presented, 35% of the neurons demonstrated directional sensitivity; the rest of the neurons (65%) were directionally insensitive. We also found a group of neurons that were capable of differentiating not only the direction of the stimulus movement along the RF but also the dimension, shape, and orientation of a complicated moving stimulus. Taking into account the data obtained, we discuss the functional role of the neurons, which demonstrated a specific (specialized with respect to a set of the parameters of visual stimulus, and not to a single parameter) response in central processing of the sensory information.     

Distribution of HLA Antigens in the Armenian Population of Nagornyi Karabakh

Characteristics of the distribution of 31 HLA antigens of classes I (A, B, and Cw) and II (DR) in Nagornyi Karabakh Armenians are reported for the first time. It has been found that the antigens most common in this population are A2, A3, A9, B5, B7, B12, Cw4, DR4, DR2, and DR3; the least common antigens are B15, B16, and B40. The results are compared with the data for Armenians living in Armenia and those for major ethnic groups. The frequencies of HLA antigens in Nagornyi Karabakh Armenians match those in Armenians living in Armenia. In the HLA-antigen distribution, Armenians are generally close to Caucasoids.     

Regulation of Natural Rubber Biosynthesis by Proteins Associated with Rubber Particles

Natural rubber, cis-1,4-polyisoprene, is an essential raw material used in thousands of products, many of which are absolutely necessary for medical purposes. Natural rubber is obtained from latex, an aqueous emulsion present in the laticiferous vessels of the natural rubber-producing plants. Hevea brasiliensis (the Brazilian rubber tree) currently is the only commercially important source of natural rubber. H. brasiliensis crops have very little genetic variability, leaving rubber plantations at risk of serious pathogenic attacks. In addition, repeated exposure to residual proteins in latex products derived from H. brasiliensis have led to serious and widespread allergic (type I) hypersensitivity. Therefore, identification of alternative sources of natural rubber is a very important biotechnological task. Potentially, Russian dandelion (Taraxacum kok-saghyz) may be such an alternative because significant amounts of natural rubber are produced in its root system. However, H. brasiliensis is a more efficient producer of natural rubber than T. kok-saghyz. Thus, improvement of rubber biosynthesis in plants is a first-priority problem of modern biotechnology. In this review, we describe proteins that may increase the concentration of natural rubber in laticiferous vessels of T. kok-saghyz and its close relative Taraxacum brevicorniculatum, when overexpressed in the plants. These proteins, cis-prenyltransferases, rubber transferase activator, and small rubber particle proteins, are directly involved in synthesis of the polyisoprene chain. We also analyze the effects of their expression levels on the production of natural rubber in vivo.     

Analysis of chloroplast <Emphasis Type="Italic">rpS16</Emphasis> intron sequences in Lemnaceae

Chloroplast rpS16 gene intron sequences were determined and characterized for twenty-five Lemnaceae accessions representing nine duckweed species. For each Lemnaceae species nucleotide substitutions and for Lemna minor, Lemna aequinoctialis, Wolffia arrhiza different indels were detected. Most of indels were found for Wolffia arrhiza and Lemna aequinoctialis. The analyses of intraspecific polymorphism resulted in identification of several gaplotypes in Lemna gibba and Lemna trisulca. Lemnaceae phylogenetic relationship based on rpS16 intron variability data has revealed significant differences between Lemna aequinoctialis and other Lemna species. Genetic distance values corroborated competence of Landoltia punctata separations from Spirodela into an independent generic taxon. The acceptability of rpS16 intron sequences for phylogenetic studies in Lemnaceae was shown.