[Expression and inheritance of a desynaptic phenotype with impaired homologous synapsis in rye].

The cytological phenotype was studied in a desynaptic form isolated from a population of rye cultivar Vyatka. The primary defect of desynaptic plants was identified as nonhomologous (heterologous) chromosome synapsis, which was observed by electron microscopy of synaptonemal complexes (SCs) in meiotic prophase I. Synapsis defects involved switches of synapsing axial elements to nonhomologous partners, asynapsis in the switching region, and foldbacks formed by the SC lateral elements. Defective bivalent formation was observed at later stages: the univalent number varied and multivalent chromosome associations were observed in single cells in metaphase I. The desynaptic phenotype was controlled by two recessive genes, sy8a and sy8b, which acted and were inherited independently. In a hybrid combination with line Ku-2/63, the desynaptic phenotype was suppressed by the dominant allele of a third gene for inhibitor I; the segregation in hybrid families corresponded to 57:7.

[Genetic collection of meiotic mutants of rye Secale cereale L].

Genetic collection of meiotic mutants of winter rye Secale cereale L. (2n = 14) was created. Mutations were detected in inbred F2 generations after self-fertilization of the F1 hybrids, obtained by individual crossing of rye plants (cultivar Vyatka) or weedy rye with plants from autofertile lines. The mutations cause partial or complete plant sterility and are maintained in collection in a heterozygous state. Genetic analysis accompanied by cytogenetic study of meiosis has revealed six mutation types. (1) Nonallelic asynaptic mutations sy1 and sy9 caused the formation of only axial chromosome elements in prophase and anaphase. The synaptonemal complexes (SCs) were absent, the formation of the chromosome "bouquet" was impaired, and all chromosomes were univalent in meiotic metaphase I in 96% (sy1) and 67% (sy2) of cells. (2) Weak asynaptic mutation sy3, which hindered complete termination of synapsis in prophase II. Subterminal asynaptic segments were always observed in the SC, and at least one pair of univalents was present in metaphase I, but the number of cells with univalents did not exceed 2%. (3) Mutations sy2, sy6, sy7, sy8, sy10, and sy19, which caused partially nonhomologous synapsis: change in pairing partners and fold-back chromosome synapsis in prophase I. In metaphase I, the number of univalents varied and multivalents were observed. (4) Mutation mei6, which causes the formation of ultrastructural protrusions on the lateral SC elements, gaps and branching of these elements. (5) Allelic mutations mei8 and mei10, which caused irregular chromatin condensation along chromosomes in prophase I, sticking and fragmentation of chromosomes in metaphase I. (6) Allelic mutations mei5 and mei10, which caused chromosome hypercondensation, defects of the division spindle formation, and random arrest of cells at different meiotic stages. However, these mutations did not affect the formation of microspore envelopes even around the cells, whose development was blocked at prophase I. Analysis of cytological pictures of meiosis in double rye mutants reveled epistatic interaction in the mutation series sy9 > sy1 > sy3 > sy19, which reflects the order of switching these genes in the course of meiosis. The expression of genes sy2 and sy19 was shown to be controlled by modifier genes. Most meiotic mutations found in rye have analogs in other plant species.

[Genetic control of chromosomal synapsis in Secale cereale L. rye meiosis: sy19 gene, causing heterologous synapsis]. / Geneticheskii kontrol' sinapsisa khromosom v meioze u rzhi Secale cerale L.: gen sy19, vyzyvaiushchii geterologichnyi sinapsis.

Analysis of manifestation and inheritance of a new mutation inducing irregular synapsis in rye showed that abnormal phenotype is determined by a recessive allele of the sy19 gene. In the homozygotes for this mutation, even at the light microscopic level, abnormal formation of bivalents is already observed at pachytene-diakinesis. At metaphase I, the univalent frequency varies from 0 to 14; in a few cells, multivalent associations of chromosomes, which are not clearly oriented in the spindle, are detected. Electron microscopy of synaptonemal complexes revealed both homologous and heterologous synapsis in homozygotes for sy19, namely partial loss of the ability to stringent homology search. Analysis of joint inheritance of sy19 and asynaptic sy1 mutations showed that they are nonallelic, inherited independently, and interact by recessive epistasis. The phenotype of double sy1sy19 mutants indicates that the sy19 gene conditioning heterologous synapsis operates at meiosis later than the synaptic gene sy1. The epistatic group of mutations, sy9 > sy1 > sy19 and sy3, was determined.

[Cytogenetic patterns in synapsis of meiotic chromosomes in animals and plants]. / Tsitogeneticheskie zakonomernosti sinapsisa meioticheskikh khromosom u zhivotnykh i rastenii.

Chromosome synapsis in meiosis is performed through the formation of a synaptonemal complex (SC). The SC aggregates homologues until the diplotene stage, when the function of physical binding is carried out by a chiasmata. SC formation is controlled by specific genes. Regularities of SC formation in animals and plants are being studied at the Laboratory of Cytogenetics, Vavilov Institute of General Genetics, the Russian Academy of Sciences. It was shown that, in Drosophila melanogaster, the presence or absence of SC in meiosis is determined by balance between autosomes and sex chromosomes. i.e., SC is formed according to regularities in sex determination. The dose of the 8C-11A segment of X chromosome plays a key role in this process. Eight mutations in synaptic genes that affect SC formation were studied in rye Secale cereale. SC variants occurring in heteromorphic sex chromosomes were analyzed in the Ellobius genera and in B-chromosomes of Apodemus peninsulae. It was shown that, in addition to homologous synapsis, non-homologous synapsis of aberrant chromosomes occurs in rye and mouse heterozygotes at chromosome rearrangements. Twice as many heterozygous chromosome rearrangements were revealed, when the SC was studied at pachytene instead of diakinesis and metaphase I. Simple methods of SC investigations extended the capabilities of cytogenetic analysis of meiosis and provided new perspectives for studying the action of meiotic gen.

[The dynamics of the formation of spontaneous autoantibodies to the synaptonemal complex in male mice]. / Issledovanie dinamiki formirovaniia spontannykh autoantitel k sinaptonemnomu kompleksu u samtsov myshi.

Time-related changes in formation of spontaneous autoantibodies against the synaptonemal complex were studied by indirect immunofluorescence in male mice. Appearance of the spontaneous autoantibodies against the synaptonemal complex coincided with that of the cells containing synaptonemal complexes. The mouse synaptonemal complexes were binding spontaneous autoantibodies of the rabbit and human sera. The synaptonemal complexes of the equine spermatocytes were binding spontaneous autoantibodies of the mouse serum. There was no fluorescence of synaptonemal complexes on preparations of spread rye meiocytes treated with the mouse serum. Antigenic similarity was shown for the synaptonemal complex components in representatives of the different mammalian orders: rodents, odd-toed ungulates, and primates.