Genetic Analysis of Mutation sy2 which Causes Nonhomologous Meiotic Synapsis in Chromosomes of Diploid Rye Secale cereale L.

Partially nonhomologous (heterologous) synapsis of meiotic chromosomes in a spontaneous desynaptic mutant form of rye is determined by two recessive genes, sy2a and sy2b, that have independent expression and inheritance. The third gene, dominant inhibitor suppressing the mutant phenotype, has been revealed in hybrid combinations between sy2 mutants and lines segregating other meiotic mutants: sy10 (heterologous synapsis), sy1, and sy9(asynapsis). All three genes determining desynapsis (sy2a, sy2b, and I) were shown to be nonallelic to monogenic mutations sy10, sy1, and sy9, inherited independently of them and expressed at later stages of prophase I than the sy10 gene. The possibility of modifying monogenic segregation of mutation sy2 by gametophyte selection for a locus linked to the gene expressed as sy2 at particular frequencies of recombination between this gene and selected locus is discussed.     

Genetic Control of Chromosome Synapsis at Meiosis in Rye Secale cereale L.: The sy19 Gene Controlling Heterologous Synapsis

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 doublesy1sy19 mutants indicates that thesy19 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.     

Genetic Analysis of Inheritance ofmei8, sy1, and sy10Meiotic Mutations in Rye Secale cereale L.

It is shown that mutations mei8 (irregular condensation and fragmentation of meiotic chromosomes),sy1(asynapsis), and sy10 (heterologous synapsis) of rye Secale cereale L. are nonallelic. In double mutants mei8 sy1 and mei8 sy10 both mutations are expressed simultaneously and independently of each other. A study of joint inheritance of mutations sy1 and sy10 revealed their interaction by means of recessive epistasis: the double mutants sy1sy10 has the sy10 phenotype. This means that the sy10 gene controls an earlier stage of synapsis in meiotic prophase than the sy1 gene. Mutation mei8is inherited independently of sy1 but it is linked to sy10 (recombination frequency 26.8 ± 3.58%).     

Abnormal Condensation of Meiotic Chromosomes Caused by the mei8 Mutation in Rye Secale cereale L.

Inheritance of two spontaneous meiosis-specific mutations with similar cytologic phenotype was studied. Both mutations were independently obtained from two rye populations (Vyatka variety and weedy rye). Both mutations are recessive, allelic, and monogenically inherited; the corresponding gene is designated mei8. The mutant alleles of the gene cause abnormal meiotic chromosome structure expressed as irregular compaction along the chromosome length, chromatin stickiness at all stages of meiosis, and chromosome fragmentation in anaphase I.     

Meiotic mutants of rye Secale cereale L. II. The nonhomologous synapsis in desynaptic mutants sy7 and sy10

We studied the expression and inheritance of two spontaneous mutations found in different populations of rye Secale cereale L. that cause high univalent frequency in meiosis and low fertility. Both mutations were inherited as monogenic recessives. For each of the mutations the corresponding gene symbols (sy7 and sy10) were suggested although their allelism has not been studied. These mutants differ in chiasma frequency and in the number of univalents per meiocyte. Electron microscopy of the wholemount surface-spread synaptonemal complexes (SCs) from microsporocytes of both mutants revealed that during meiotic prophase I random synapsis began and progressed that involved not only homologous but also nonhomologous chromosomes. SCs were formed with frequent changes of pairing partners (switches) and intrachromosomal foldbacks of unpaired axial elements. As a result, incompletely synapsed, non-homologous and multivalent SCs were formed in mutants by the stage analogous to pachytene in normal plants. In sy7 a maximum in the number of switches and foldbacks were observed at zygotene, whereas in sy10 this occurred at pachytene. We suggest that it is the process of recognition of homology that is impaired in both mutants. This leads to indiscriminate synapsis and prevents chiasma formation. Both mutants may be classified as desynaptic.     

Opaline Silica Deposition in Rye (Secale cereale L.)

The types of opaline silica-bodies (opal phytoliths) which occurin the mature prophylls, radical and culm leaves, culms, andinflorescence bracts of rye (Secale cereale L.) are describedand figured. Silica-bodies are absent from the coleoptile, andthe adaxial epidermis of the prophylls, leaf sheaths, and inflorescencebracts. The stages of silica-body formation in young radicalleaf sheaths are also described. Alternative hypotheses forthe origin of silica-bodies are discussed.     

The expression of mutation sy2 causing nonhomologous synapsis in meiosis of diploid rye Secale cereale L

The cytological expression of spontaneous mutation sy2 isolated from a population of weedy rye was examined. It was demonstrated that the primary defect of meiosis in the mutant plants is nonhomologous synapsis, which occurs simultaneously with the homologous one. An electron microscope study of the synaptonemal complex (SC) at prophase I showed synaptic abnormalities that manifested as "switches" of synapting axial elements to the nonhomologous partner and the formation of foldbacks of lateral SC elements. The sy2 mutants are characterized by one to two such events per meiosis. Nonhomologous synapsis leads to the appearance of univalents at metaphase I (on average 4.16 +/- 0.022 per meiocyte) and multivalents (on average 0.12 +/- 0.007 per meiocyte). The presence of multivalents in 12.0% of meiocytes at metaphase I may result from recombination in ectopic regions of homology. It is suggested that the sy2 mutation impairs a component of the system that limits synapsis in meiocytes to only homologous chromosome pairs.     

The Pattern and Sequence of Opaline Silica Deposition in Rye (Secale cereale L.)

The pattern of opaline silica deposition in the leaves and internodesof rye (Secale cereale L.) has been studied by means of countsof silica-bodies in cleared epidermal preparations. Silica depositionoccurs during the maturation process when the leaves are fullyexpanded. The increase in total silica content and changes inthe ‘free’ and residual silica fractions of theleaves during their growth period have been determined usinga colorimetric estimation.     

The Study of Joint Inheritance of Mutations Impairing the Structure of Meiotic Chromosomes in Rye Secale cereale L.

Genetic analysis has demonstrated that meiotic mutations mei8 (irregular condensation and fragmentation of meiotic chromosomes) andmei10 (chromosome overcompaction) are nonallelic. Mutation mei10 exhibits digenic inheritance (with a segregation ratio of 13 : 3) in the combinations of crosses studied. It is assumed that the phenotypic expression of mutation mei10is suppressed by the effect of recessive genelch1 or lch2 (long chromosomes), both of which have been revealed in one of the parental lines (Mc10). These genes determine weak condensation of meiotic chromosomes. In double mutantsmei8 mei10, the mutations are expressed independently of each other. Gene mei10 is linked with gene mei8(r^ = 36.8 ± 5.38%); genes lch1 and lch2 are not linked either with them or with each other. Taking into account the data on the linkage between genes mei10and sy10 and between mei8andsy10, the order of genes in the linkage group is shown to be the following: mei8–sy10–mei10.     

Genetic analysis of mutation sy2 which causes nonhomologous meiotic synapsis in chromosomes of diploid rye Secale cereale L

Partially nonhomologous (heterologous) synapsis of meiotic chromosomes in a spontaneous desynaptic mutant form of rye is determined by two recessive genes, sy2a and sy2b, that have independent expression and inheritance. The third gene, dominant inhibitor suppressing the mutant phenotype, has been revealed in hybrid combinations between sy2 mutants and lines segregating other meiotic mutants: sy10 (heterologous synapsis), sy1, and sy9 (asynapsis). All three genes determining desynapsis (sy2a, sy2b, and I) were shown to be nonallelic to monogenic mutations sy10, sy1, and sy9, inherited independently of them and expressed at later stages of prophase I than the sy10 gene. The possibility of modifying monogenic segregation of mutation sy2 by gametophyte selection for a locus linked to the gene expressed as sy2 at particular frequencies of recombination between this gene and selected locus is discussed.     

Somatic embryogenesis in polyembryonic Secale cereale L.

Summary The progeny of polyembryonic Secale cereale L., was used to study the in vitro response of the immature embryos. The formation of embryogenic calli was very high, and this response and its distribution was statistically different to that shown by the normal regenerated plants and the original population. This behaviour seems to be related to a genetic condition which favours the presence of supernumerary embryos, in vivo as well as in vitro.     

Analysis of Glucocerebrosides of Rye (Secale cereale L. cv Puma) Leaf and Plasma Membrane

Glucocerebrosides of whole rye (Secale cerale L. cv Puma) leaf and plasma membrane were analyzed using gas chromatography-mass spectrometry and gas chromatography following hydrolysis or as intact molecules purified by reverse-phase high performance liquid chromatography. Fatty acids of acid-hydrolyzed leaf and plasma membrane glucocerebrosides consisted of >98 weight percent saturated and monounsaturated 2-hydroxy fatty acids which contained 16 to 26 carbon atoms. The major fatty acids detected were 2-hydroxynervonic acid (24:1h), 2-hydroxylignoceric acid (24:0h), 2-hydroxyerucic acid (22:1h), and 2-hydroxybehenic acid (22:0h). Long-chain bases of alkaline-hydrolyzed glucocerebrosides consisted primarily of cis-trans isomers of the trihydroxy base 4-hydroxysphingenine (t18:1) and the dihydroxy base sphingadienine (d18:2) with lesser amounts of 4-hydroxysphinganine (t18:0) and isomers of sphingenine (d18:1). Intact, underivatized glucocerebroside molecular species of rye leaf and plasma membrane were separated into more than 30 molecular species using reverse-phase HPLC. The molecular species composition of leaf and plasma membrane were quantitatively and qualitatively similar. The major molecular species was 24:1h-t18:1 which constituted nearly 40 weight percent of leaf and plasma membrane extracts. Several other species including 22:1h-t18:1, 24:1h-t18:1 (isomer), 22:0h-t18:1, 24:1h-d18:2, and 24:0h-t18:1 each comprised 4 to 8% of the total. It is anticipated that the high performance liquid chromatography procedure developed in this study to separate intact, underivatized lipid molecular species will be useful in future studies of the physical properties and biosynthesis of plant glucocerebrosides.     

Meiotic mutants of rye Secale cereale L.

Summary A mutant form of weedy rye characterized by male and female sterility and having a hereditary block in the chromosome synapsis has been found and described. Genetic analysis has shown the synapsis block to be determined by the recessive allele of a gene designated as sy-1. Electron microscopy of surface-spread microsporocyte nuclei revealed the complete absence of the synaptonemal complex over the whole meiotic prophase I, although the axial cores were perfectly formed by each chromosome. Only univalents were observed at metaphase I, their average number ranging from 13.1 to 14.0 per cell. A precocious distribution of univalents at the poles is observed at metaphase I. All of the later stages of meiosis were irregular and resulted in the formation of abnormal microspores. Thus, the mutant proves to be asynaptic because of the blocked initiation of synapses at prophase I.     

Genetic control of chromosomal synapsis in Secale cereale L. rye meiosis: sy19 gene, causing heterologous synapsis

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.     

Extraction and Isolation of Antifreeze Proteins from Winter Rye (Secale cereale L.) Leaves

Apoplastic extracts of cold-acclimated winter rye (Secale cereale L. cv Musketeer) leaves were previously shown to exhibit antifreeze activity. The objectives of the present study were to identify and characterize individual antifreeze proteins present in the apoplastic extracts. The highest protein concentrations and antifreeze activity were obtained when the leaf apoplast was extracted with ascorbic acid and either CaCl2 or MgSO4. Seven major polypeptides were purified from these extracts by one-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis under nonreducing conditions. The five larger polypeptides, of 19, 26, 32, 34, and 36 kD, exhibited significant levels of antifreeze activity, whereas the 11- and 13-kD polypeptides showed only weak activity. Five of these polypeptides migrated with higher apparent molecular masses on SDS gels after treatment with 0.1 M dithiothreitol, which indicated the presence of intramolecular disulfide bonds. The apparent reduction of the disulfide bonds did not eliminate antifreeze activity in four of the polypeptides that contained intramolecular disulfide bonds and exhibited significant levels of antifreeze activity. The amino acid compositions of these polypeptides were similar in that they were all relatively enriched in the residues Asp/Asn, Glu/Gln, Ser, Thr, Gly, and Ala; they all lacked His, except for the 26-kD polypeptide, and they contained up to 5% Cys residues. These polypeptides were examined with antisera to other cystine-containing antifreeze proteins from fish and insects, and no common epitopes were detected. We conclude that cold-acclimated winter rye leaves produce multiple polypeptides with antifreeze activity that appear to be distinct from antifreezes produced by fish and insects.     

Allozyme variation in rye,Secale cereale L.

Summary Eleven samples of eight European commercial varieties of winter rye were examined at eight polymorphic enzyme loci. Genotype frequencies fitted Hardy-Weinberg expectations at all loci in all samples studied. Of the total genetic diversity recorded at the 8 loci, only 7% was expressed between varieties. Allele frequency differences between varieties were, however, sufficient to allow a characterization of each variety by a specific set of allele frequencies. Using subsets of the original data, it could be demonstrated that all pairs of varieties but one still showed significant allozyme differences, when only 4 loci were screened in samples half the original size of 200 individuals. Even when only one locus was analyzed, all varieties but two were distinguishable, but this diagnostic locus was not identical in all pairwise comparisons.     

Genetic analysis of inheritance of mei8, sy1 and sy10 mutations,disrupting the correct meiosis in the rye Secale cereale L

It is shown that mutations mei8 (irregular condensation and fragmentation of meiotic chromosomes), sy1 (asynapsis), and sy10 (heterologous synapsis) of rye Secale cereal are nonallelic. In double mutants mei8 sy1 and mei8 sy10 both mutations are expressed simultaneously and independently of each other. A study of joint inheritance of mutations sy1 and sy10 revealed their interaction by means of recessive epistasis: the double mutants has the sy10 phenotype. This means that the sy10 gene controls an earlier stage of synapsis in meiotic prophase than the sy1 gene. Mutation mei8 is inherited independently of sy1 but it is linked to sy10 (recombination frequency 26.8 +/- 3.58%).     

Genetic mapping of isozyme loci in Secale cereale L.

Summary The genetics and linkage relationships of several isozymatic and morphological markers have been investigated in different cultivars of rye (Secale cereale L.). The inheritance and the variability among cultivars of three new isozymatic zones are described: GOT2 and LAP, each of them under the control of a two-allele single locus, namely Got2 and Lap, respectively; and 6PGD1 controlled by two loci, 6Pgd1a and 6Pgd1b, which have alleles in common. Four linkage groups have been found: Acp2-Acp3, Got3-Mdh2-Lper4, Mdh1-6Pgd2-Pgi2, and Pgm-Eper2-[Eper1-Eper3]. The assignment of these four groups to the chromosomes 7R, 3R, 1R, and 4R is discussed.     

The Banding Pattern of the Rye (Secale cereale) Chromosomes and Its Application

The Giemsa C-banding technique has been used in this paper for analysis of chromosome banding pattern, and the changes of the chromosome structures of irradiated rye and wheat-rye were identified preliminarily. Heterochromatin polymorphism of rye was also discussed.     

Involvement of Plasma Membrane Alterations in Cold Acclimation of Winter Rye Seedlings (Secale cereale L. cv Puma)

Using plasma membranes with high purity isolated from winter rye seedlings (Secale cereale L. cv Puma) by an aqueous two-polymer phase partition technique, lipid and protein changes were determined during the development of cold hardiness.