Pairing and synapsis in wild type Arabidopsis thaliana

Abstract

A spreading technique was used to perform a structural analysis of prophase I nuclei in pollen mother cells (PMCs) of wild-type Arabidopsis thaliana. In leptotene, all chromosomes developed fully axial elements before a presynaptic alignment was observed. Pairing and synapsis start in regions close to the telomeres at early zygotene. Interstitial synaptonemal complex (SC) stretches were found to occur at several sites per bivalent at mid zygotene. Within individual bivalents, extensive regions of SC formation often existed at the same time as other extensive regions that were unsynapsed. Also in the same nucleus, one bivalent might have several SC segments, while other bivalents have only a few. The classical bouquet was not so evident as in other plant species. Length measurements of the five pachytene bivalents have allowed the elaboration of a pachytene karyotype. Pachytene chromatin compaction in Arabidopsis was significantly less than that observed in the other species analysed and this is paralleled with a higher recombination rate (centimorgans per megabase).

Chromosome Dynamics in Meiotic Prophase I in Plants

“…1 C) [Anderson et al, 2003;Lopez et al, 2008]. Serial sections can be used to analyze the nucleus in 3 dimensions [Gillies, 1973].…”

“…However, 3D reconstruction of fine sections is very difficult and laborious and, therefore, this method is not well suited for analyzing rapid chromosome dynamics. For this reason most studies on meiotic chromosomes in plants using EM have been done with the spreading technique [Gillies, 1981;Anderson et al, 2003;Lopez et al, 2008]. Antibodies coupled with gold particles can be used for protein immunolocalization in EM [Anderson et al, 1997;Lohmiller et al, 2008] although, inevitably, the number of different antibodies that can be used at the same time is very limited.…”

“…before pairing commences along chromosome arms [Roberts et al, 2009]. In many plant species telomeric regions are also sites where synapsis first initiates [Stack and Anderson, 2002;Lopez et al, 2008]. Recent studies on chromosome motility in meiotic prophase point, however, to another possible role for telomere clustering.…”

Homoeologous Chromosome Sorting and Progression of Meiotic Recombination inBrassica napus: Ploidy Does Matter!

“…The synaptonemal complex spreads were prepared according to the protocol described by López et al (2008) with minor modifications: 0.05% (v/v) Triton X-100 + 0.1% (v/v) Lipsol detergent was included in the swelling medium. The slides were stained with aqueous AgNO 3 (40%, w/v) at 45°C and examined under an electron microscope (Jeol 1010).…”

Chiasma Frequency Is Region Specific and Chromosome Conformation Dependent in a Rye Chromosome Added to Wheat

“…Almost all crossovers detected in the construction of genetic maps of rye, wheat and barley concentrate in the distal half of the chromosome arms Lukaszewski, 1992;Lukaszewski and Curtis, 1993;Gill et al, 1996a, b;Künzel et al, 2000;Saintenac et al, 2009]. The ultrastructural analysis of SC formation demonstrated that the commencement of pairing at distal sites and succession by numerous intercalary initiations is common to many plant species, regardless of the distribution of chiasmata [Gillies, 1975[Gillies, , 1985Holm, 1977Holm, , 1986Albini and Jones, 1987;Martínez et al, 2001a, b;López et al, 2008].…”