Synaptonemal Complex of Haploid Maize

Abstract

Since the application of electron microscopy in the study of chromosomes of eukaryotes, results have not been as expected. For instance, electron microscope has failed to reveal the structural characteristics of the chromosomes related to these that were observed with light microscope, and electron microscope has not substantiated the conclusions generalized with cytogenetic researches. Further more, there is still no unified concept of the unit structure of chromosomes at fine structure level. However, in 1956, reports on the finding of synaptonemal com plex in the meiotic prophase of crayfish by Moses (1956) and in that of cat, pigeon and man by Fawcett (1956) were independently published. These subsequently stimulated a great deal of studies on this complex in various organisms. In spite of this, studies of the meiotic chromosomes of haploid eukaryotes have not been made except that of haploid tomato by Menzel and Price (1966). In view of the lack of knowledge on this particular aspect, this investigation was prompted. Materials and proceduresThe brief procedures are as follow: One of the three synchronously developed anthers of a spikelet from the male inflorescence of haploid maize (Zea mays L.) was fixed in 3% glutaraldehyde in 0.025 M phosphate buffer at pH 6.8 for one hour, then washed in phosphate buffer and postfixed in 1% osmium tetraoxide in 0.05 M phosphate buffer at pH 7.0 for two hours; while the other two anthers of the same, fixed in aceto-alcohol fixative. The haploid plants were obtained by the employ ment of the material and techniques developed by Coe and Sarkar (1964). The division stage of the glutaraldehyde-fixed anthers was determined through observa tions with light microscope of the aceto-alcohol fixed anthers by standard aceto carmine squash preparations. Only these anthers at pachytene stage of divisions were selected for electron microscopy. The standard procedure of Epon-embedding and uranyl and lead salt-stainings were followed throughout the study. Results and explanationsSynaptonemal complex resembled the one found in diploid maize (Underbrink, Ting and Sparrow 1967, Ting 1969) was consistently observed at pachytene stage of meiotic prophase of all 11 haploids studied. At frontal view, three elements: two lateral elements and one central element, could be readily identified. The diameter of the two lateral elements measured 250 A while that of the central ele

Chromosome pairing analysis in haploid wheat by spreading of meiotic nuclei

“…These concepts have been supported by ultrastructural studies, documenting the presence of synaptonemal complexes in haploids of e.g. maize (27) and Petunia and Antirrhinum (24). In monohaploids of barley up to 60% of the complement was combined with a synaptonemal complex (5).…”

Meiosis in haploid rye: extensive synapsis and low chiasma frequency

“…Whereas random bivalent formation has been suggested by Govindaswami & Pachytene observations by light microscopy revealed occasional interchromosomal and intrachromosomal pairing in monoploids of rice (Chu, 1967), tomato (Ecochard et al, 1969), maize (Ting, 1966;Ford, 1970;Weber & Alexander, 1972) and barley (Sadasivaiah & Kasha, 1971, 1973. These findings were corroborated by studies based on threedimensional reconstruction of pachytene nuclei by electron microscopy that revealed the existence of synaptonemal complexes (SCs) in monoploids of tomato (Menzel & Price, 1966), maize (Ting, 1973), petunias and snapdragons (Sen, 1970) and barley (Gillies, 1974). However, with this methodology only a limited number of nuclei can be analysed, which prevents a quantitative study of SC formation.…”

Chromosome pairing in triploid females of Bombyx mori analyzed by three dimensional reconstructions of synaptonemal complexes

“…Several cases are known however, where extensive chromosome pairing with synaptonemai complexes occurs between apparently non-homologous chromosome segments. Synaptonemal complexes are readily observed in haploid maize (46,47), barley (8), Petunia and Antirrhiuum (36), and tomato 08). In haploid barley, up to 60% of the lateral component length is paired into synaptonemal complexes, which are morphologically indistinguishable from complexes between homologous chromosomes (8).…”

“…Studies on chromosome pairing in haploid organisms (5,8,36,47) have demonstrated that extensive, presumably non-homologous, chromosome pairing can occur, and in barley may include up to 60% of the lateral components. Synaptonemal complexes between non-homologous chromosomes are morphologically indistinguishable from complexes between homologous chromosomes (8).…”