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Laboratory of Experimental Modeling of Evolutionary Processes


Head V.A.Berdnikov, Ph.D.
berdnik@bionet.nsc.ru





Distributions of the width of flat tendrils in three pea lines differing by alleles of the his1 gene of the most abundant subtype 1 of H1 histone and hemizygous for the Tl gene. Delta-s line possesses the slow allelic variant of subtype 1, Delta-f _ the fast variant, delta is heterozygous



A scheme for the karyotype and genetic markers of the original stable trisomic pea line Trust for chromosome 2 (solid line), 5 (dashed line) and exchange chromosome 25

Distribution of seedling length (cm) in the F2 - F7 generations


Evidence is increasingly supporting Darwin's view that organisms have evolved mainly through accumulation of mutations with slight phenotypic effects. The genes that govern transcriptional machinery functioning and are capable of affecting many organism traits are of primary evolutionary importance. Such may be the histone 1 (H1) genes recently shown to be involved in the systems controlling development in multicellular organisms.

Extensive analysis of the variations in the electrophoretic mobility of H1 histone in insect orders was performed at the Laboratory. The analysis showed that molecular changes in H1 were regularly involved in speciation. We found no intraspecific polymorphism for H1 histone in insects but revealed that it is extremely polymorphic in the majority of the studied legume species of the Vicieae tribe. We chose the garden pea, the oldest genetic object, as a convenient experimental tool.

We found that pea histone H1 possesses 7 subtypes, represented by several allelic variants each. We showed that the allelic variant of subtype 1 differs by insertion/deletion of a tandem repeat of 6 amino acids in the C-terminal domain of the molecule. We mapped all the 7 genes at the 3 loci.

We obtained several pairs of isogenic pea lines differing only by the alleles of distinct histone genes and demonstrated statistically significant differences between the lines for some quantitative traits. Furthermore, we found that a substitution of a short segment of chromosome 5, containing the His locus of subtype 1, has a strong (about 20%) effect on the expression of the tl homeotic gene that converts tendrils into leaflets. After 10 backcrosses, we obtained a series of isogenic lines differing by the haplotypes of the His4-His6 gene of the His(2-6) gene cluster, including the haplotypes lacking the expression of certain subtypes and demonstrated the effect of sequential switching off of the expression of several genes on quantitative traits. In addition to pea, we obtained pairs of isogenic lines of lentil and grass-pea differing by the allelic variants of the most abundant H1 histone subtype that occurred in the genetically homogenous material as a result of a spontaneous insertion/deletion of a repeated segment in the C-terminal domain (lentil) and in the N-terminal domain (grass-pea). These lines showed significant differences for some quantitative traits, including seed productivity.

We studied the territorial distribution of the histone H1 alleles in aboriginal pea cultivars of the Old World and revealed a high correlation between temperature and the frequency of one of the alleles of subtype 5. In another legume plant, Vicia unijuga, we found a radial cline of the allelic frequencies of histone H1 in the territory of Novosibirsk Academy Town, most probably, caused by man-made factors. Thus, we showed that changes in the molecular structure of histone H1 produce phenotypic changes that can be made apparent by natural selection.

To increase variability in the dosage of genes with strong pleiotropic effect, we developed stable trisomic lines of pea whose genome contains a small genetically marked chromosome. We intend to use these lines to produce an artificial B-chromosome reproducing the way which chromosome emerged in the course of evolution according to the theory we developed. Artificial chromosomes may serve as chromosomal vectors in breeding of new promising forms of plants.

Interest centers on two aspects of the Breeding Theory at the Section of the Bases of Plant Breeding (Head S.F.Koval)

1. Methods for constructing cultivar models

Series of near-isogenic (73 specimens) and alloplasmic (43 specimens) lines were developed using spring common wheat Novosibirskaya 67. These lines are used for determining the contribution of a character to the yield (cultivar model), mapping genes, and as donors for breeding. These lines were used to developed cv. Tertsiya, now commercially available in Siberia. All these near-isogenic lines are stored with the international gene bank CYMMIT and are available free of charge to all researchers.

These near-isogenic lines are used for PCR-based location of a new gene coding for immunity to leaf rust (Lr). Two lines with chlorina gene marking the monosomic state of homeologous group 7 chromosomes were developed. Near-isogenic lines were used to find multiple Vrn1 (5A) alleles, developed further as individual near-isogenic lines.

In parallel, genetics of barley salt tolerance is studied, and monogenic tester lines with these character are bred.

2. Untraditional selection methods

A method of complex selection on challenging backgrounds was suggested. This method allows - a drastic increase in the efficiency of primary selection and its transfer from field to laboratory.

Gametophytic genes, interrelations of gametophyte and sporophyte during pollination and fertilization, and evolutionary and applied aspects of gametic selection are being studied for many years in sugar beet and barley. The data obtained, were used to develop the technique for gametophytic selection of barley for increased salt tolerance.