[Analysis of the meiotic recombination frequency in transgenic tomato hybrids expressing recA and NLS-recA-licBM3 genes].

To study and induce meiotic recombination in plants, we generated and analyzed transgenic tomato hybrids F1-RecA and F1-NLS-recA-LicBM3 expressing, respectively, the recA gene of Escherichia coli and the NLS-recA-licBM3 gene. It was found that the recA and NLS-recA-licBM3 genes are inherited through the maternal and paternal lineages, they have no selective influence on the pollen and are contained in tomato F1-RecA and F1-NLS-RecA-LicBM3 hybrids outside the second chromosome in the hemizygous state. The comparative analysis of the meiotic recombination frequency (rf) in the progenies of the transgenic and nontransgenic hybrids showed that only the expression of the recA gene of E. coli in cells of the F1-RecA plants produced a 1.2-1.5-fold increase in the frequency of recombination between some linked marker genes of the second chromosome of tomato.

[Transgenic tomato plants expressing recA and NLS-recA-licBM3 genes as a model for studying meiotic recombination].

Homologous DNA recombination in eukaryotes is necessary to maintain genome stability and integrity and for correct chromosome segregation and formation of new haplotypes in meiosis. At the same time, genetic determination and nonrandomness of meiotic recombination restrict the introgression of genes and generation of unique genotypes. As one of the approaches to study and induce meiotic recombination in plants, it is recommended to use the recA gene of Escherichia coli. It is shown that the recA and NLS-recA-licBM3 genes have maternal inheritance and are expressed in the progeny of transgenic tomato plants. Plants expressing recA or NLS-recA-licBM3 and containing one T-DNA insertion do not differ in pollen fertility from original nontransgenic forms and can therefore be used for comparative studies of the effect of bacterial recombinases on meiotic recombination between linked genes.

[Thermostable lichenase as a translational reporter].

Hybrid genes containing the reporter gene for thermostable lichenase and model genes recA, recA1, cry3a, cry3aM, and ssp1 were constructed. The expression of these genes was studied in prokaryotic and eukaryotic cells. The presence of lichenase in the hybrid proteins was shown to facilitate analysis of the hybrid protein expression in transgenic organisms. Owing to high relative activity and thermostability of lichenase, the activity of this enzyme can be measured by simple, rapid and sensitive qualitative and quantitative methods that do not require costly equipment and reagents. Using the zymograms method, molecular masses of the lichenase-containing hybrid proteins can be precisely estimated. This method is proposed instead of Western blotting using lichenase as a translational reporter. Our results showed that the use of thermostable lichenase as a translational reporter yields the data that are problematic to obtain using traditional methods of gene expression analysis, which is of importance for fundamental and applied research.

[Efficiency of feedback selection for recombination in Drosophila]. / Effektivnost' sopriazhennogo otbora po rekombinatsii u Drozofily.

A number of theoretical models have been developed in population genetics to explain the evolution of recombination system under natural selection for adaptive traits. Using Drosophila cage populations of large size the effect of selection for resistance to daily temperature fluctuations on the rec-system was studied in this work. It is established that selection for population adaptability to extreme conditions leads during several tens of generations to significant increase in crossing-over rate within various parts of the genome (especially in b-cn and ru-h of chromosomes 2 and 3), as well as to relaxation of exchange interference for adjacent and non-adjacent segments. The Fisher's theoretical prognosis about tightening of linkage in optimal constant conditions was experimentally confirmed for the first time.

[Evolution of the dominance of rec-loci. A mathematical model]. / Evoliutsiia dominantnosti rec-lokusob. Matematicheskaia model'.

The possibility of evolutionary explanation of dominance relations for alleles in selective-neutral rec-loci was explored by means of numerical experiments. It was shown that selection for two-loci fitness system causing the secondary (induced) selection for the rec-system, results in changing the allele frequency of the second-level modificator gene controlling the dominance relations in the rec-locus. The dominance of rec-allele, providing the favourable for the given conditions level of crossing-over between selected fitness loci, is established, due to these changes. It was found that the neutral dominance modificator can influence the dynamics of the whole system.

The evolutionary role of the dependence of recombination on environment : Two and three loci models.

The recombination frequency (rf) is known to be dependent not only on genetic background, but on the environment as well. In our numerical experiments we examine the role of the dependence of recombination on environment in the evolution of the genetic system. Variable rf-strategies, ensuring mean fitnesses greater than the optimum constant rf(*)-level, exist in both cyclical and stochastic environments. The conclusion that environment dependent recombination is evolutionary advantageous can be shown to be valid when variation in the frequency of recombination modifiers rather than mean fitness (which implies the concept of group selection) is used as a criterion for strategy comparisons. In this case, an evolutionary advantageous type of variable rf-strategies is the one ensuring restricted genetic variability dispersion in an optimal environment and an increase in released variation with the deterioration of environmental conditions. Another important result is that, taking into account the dependence of recombination on environment, it is possible to account for the maintenance of a higher level of population recombination than that predicted by models with the constant rf-level. On the whole, the data obtained indicate that the direct influence of external factors upon the rf-value could have been a significant factor in the evolution of the genetic system.

Ecological aspects of the recombination problem.

Some consequences of the effect of environmental factors on the recombination system are dealt with in this paper. There are two components involved - the system of individual adaptation (F-system) and the genetic system of population adaptation (R-system). Their interaction offers an optimum interrelation of immediate adaptivity and genetic flexibility within the population. Familiar data on the evolution of recombination control systems are considered in connection with the problems of induced broadening of genotypic variation spectrum with a view to selection.A notion of combined recombination rate and spectrum control is introduced here: disturbance control-due to direct influence of environmental factors on R-system (including meiotic processes), negative feedback control - due to dominance-recessiveness relationship between rec-loci alleles of the "fine" control system, and to the dependence of the R-system on the F-system norms of reaction to environment variation. The problem of dependence of the recombination spectrum on environmental factors has been considered and the hypothesis of a possible mechanism of such a dependence suggested.