A mutation, tl2, in pea (Pisum sativum L.) affects leaf development only in the heterozygous state.

After gamma irradiation of pea seeds, a mutation designated as tendril-less2 (tl2) was induced. In the heterozygous state, it transforms tendrils into very narrow leaflets that resemble the heterozygote phenotype of the classic tl mutation. The tendrils of the double heterozygote tl2/+, tl/+ are converted into oval leaflets. Unlike tl, the novel mutation in the homozygous state does not affect tendrils. The leaf phenotype of homozygotes tl2/tl2 and Tl2/Tl2 do not differ in the tl/+ background. However, the anthocyanin pigmentation is strongly suppressed in petals of tl2/tl2 plants. Some hypotheses to explain the unusual phenotypic manifestation of tl2 are suggested.

Tertiary trisomics in the garden pea as a model of B chromosome evolution in plants.

It is hypothesized that, in plants, genetically empty B chromosomes may originate from the extra chromosome (E) of tertiary trisomics if (i) the region of basic chromosomes homologous to the E (H-region) harbors a sporophytic lethal covered by the wild-type allele in E, and (ii) crossing-over between E and the H-region is suppressed. Under these conditions, most loss-of-function mutations occurring in the H-region are deleterious for haploid gametophytes, whereas those occurring in E are neutral or advantageous for hyperploid (n+1) gametophytes. As a result, natural selection at the gametophyte level can lead to the degeneration of E, leaving the H-region intact. Using Hammarlund translocation T(3-6)a, we synthesized two trisomic lines of the garden pea (Pisum sativum L.), where E was composed of the short arms of chromosomes 3 and 6 and the H-region carried recessive markers. In the trisomic line TRIS, we found few crossovers between E and the H-region. In the trisomic line TRUST, obtained after a change of basic chromosome constitution, recombination in this region was completely suppressed. After induction in the H-region of TRUST of a recessive sporophytic mutation rmv, two 15-chromosome lines of stable trisomics were established. One of them passed 11 generations, having produced more than 6000 individuals, all of them trisomic, and E remained present as a single element with no pairing partners. No tetrasomics were detected in these lines. If such trisomics occurred in nature, their extra chromosomes are likely to become a B chromosome.

[Structural characteristics of lysine-rich histone from the sperm of a mollusk Anodonta piscinalis]. / Osobennosti stroeniia bogatogo lizinom gistona spermy bezzubki Anodonta piscinalis.

Sperm of freshwater bivalve mollusk Anodonta piscinalis was found to contain two fractions of lysine-rich histone: somatic histone H1 and sperm-specific protamine-like histone, named Hp. A detailed analysis of H1 and Hp structure was carried out by means of N-bromosuccinimide, chymotrypsin and pepsin cleavage followed by determination of the lysine residue number, positive charge and molecular length of obtained fragments by the method of incomplete succinylation. It has been shown, that Anodonta histone H1, like the avian histone H5, contains 3 tyrosine residues in the central hydrophobic domain of the molecule. Histone Hp contains 5 tyrosine residues, 3 of which are localized in the hydrophobic domain, while the rest two--in the COOH-terminal part of the molecule, characterized by a strong positive charge. Such unusual disposition of tyrosine residues in the lysine-rich histone has been found for the first time. All the regions of histone Hp molecule contain a great number of arginine residues. The only phenylalanine residue is localised approximately in the middle of the polypeptide chain for both H1 and Hp molecules. On the basis of structure homology between histones H1 and Hp the origin of Hp from H1 in the course of evolution is proposed.

[Molecular variants of histone H5 of linnet (Acanthis flammea)]. / Molekuliarnye varianty gistona H5 chechetki (Acanthis flammea).

Five electrophoretic variants of H5 histone were detected in the population of linnet (Acanthis flammea). Using the method of incomplete succinilation the number of lysine residues, electrophoretic positive charge and molecular length were determined for some variants of H5 histone and for their fragments, obtained after treatment with n-bromosuccinimide and chymotrypsin. The difference in structure of H5 variants was found to be connected with the region, confined by the phenylalanine residue and the C-end of the molecule. The minimal difference in molecular length of fragments carrying the variable region was found to be 6 amino acids, two of them are basic. A series of "regular" fragments was detected after mild treatment with trypsin. The number of these fragments increased in parallel with the increase of histone length. In accordance with the scheme proposed, the difference in structure of linnet H5 variants is caused by insertion of the regular region consisting of tandem repeats (from 3 to 7 times) of the elementary hexapeptide.

[Study of evolutionary changes in subfraction composition of histone H1 in birds]. / Issledovanie evoliutsionnykh izmenenii v subfraktsionnom sostave gistona H1 ptits.

Analysis of electrophoretic mobility of histone H1 subfractions from liver, brain and erythrocytes of 41 bird species was carried out. Subfractions of erythrocyte H1 histones from each species were compared with those of thrush Turdus musicus. The majority of species proved to possess a set of electrophoretically similar subfractions. Interspecific differences in histone H1 were mainly due to the differences in the ratio of those subfractions. The identity of the electrophoretic mobility and similar contribution to H1 histone from the respective tissues in different species permits to consider certain subfractions as homologous ones. The conservation of electrophoretic mobility for homologous subfractions of the birds of different orders shows a high evolutionary conservatism of the corresponding genes. It seems that in the course of evolution only a change in the expression of some of those genes occurs.

Study of the relationship between the subfraction composition of histone F1 and the type of tissue in birds.

The subfraction composition of lysine-rich histone has been studied with the aid of polyacrylamide gel electrophoresis. The subfraction compositions of the histone F1 of several tissues from the chicken, pigeon, and titmouse have been compared. The histone F1 from the tissues investigated consists of four or five subfractions of similar number and electrophoretic mobility (1, 1a, 2, 3, and 4). In the different avian species each subfraction varied its mobility independently of the others. The chicken tissues investigated can be divided into two classes, depending on the relative concentration of subfractions 2 and 3 (A and B): Class A (subfraction 2 is smaller than 3) includes the brain, liver, skeletal muscle, heart, muscular layer of the stomach, and pancreas, and class B (subfraction 2 is larger than 3) includes the intestinal mucosa, thymus, and testes, as well as the liver, heart, and pancreas from a 21-day embryo. Such a division of the tissues corresponds to the varying rate of their cellular renewal. In a parallel examination of the relative concentrations of the individual subfractions in the same tissues from the three avian species it has been found that the relative concentration of subfractions 3 and 2 is increased in the skeletal muscles, heart, brain, and liver, that subfraction 2 is increased in the intestinal mucosa, that subfractions 4 and 3 are increased in the pancreas, and that subfractions 1, 1a, and 4 are increased in the erythrocytes. The results obtained may be interpreted as a consequence of some relationship between the subfraction composition of histone F1 and the type of tissue of the source.

[Changes in subfraction composition of chicken lysine-rich histone during ontogenesis]. / Izmeneiia v subfraktsionnom sostave lizin-bogatogo gistona kur v khode ontogeneza

Lysine-rich histone isolated from different chicken tissues was separated electrophoretically into 4-5 subfractions. The subfrations reffered to as 1, 2, 3, and 4, occur in each the tissue studied, erythrocyte lysine-rich histone containing an additional subfraction 1a. F1 histone from mitotically active tissues (intestinal mucosa, thymus, testes) has a higher content of subfraction 2, while the same histones from mototically inactive tissues (liver, heart, brain) contain an elevated amount of subfraction 3. F1 histone isolated from liver, brain and heart of 21-day embryo has much more of subfraction 2, than the same histone of adult animal. During the chicken development from hatching till maturation the content of subfraction 2 in these organs decreases, and the content of subfraction 3 increases. The rate of this change in liver corresponds to the rate of DNA synthesis. In F1 histone of erythrocytes the content of subfraction 4 falls down during the post hatching ontogenesis.

[A study of ratios between histone fractions]. / Izuchenie kolichestvennykh sootnoshenii mezhdu gistonovymi fraktsiiami

The amount of individual fractions in the whole histone isolated from the blood of hen, frog (Rana ridibunda), bream (Abramis brama), from rat thymus and from the locust (Schistocerca gregaris) was studied quantitatively. It is shown that the ratios between fractions F2a1, F2b, F2a2 and F3 are fixed. The share of each fraction in the sum of fractions F2a1, F2b, F2a2, F3 was found to be approximately 22.5, 30.5, 21.0 and 26.0 per cent, respectively. The share of the fraction F1 can variate within a rather wide range.