The Arabidopsis HOP2 gene has a role in preventing illegitimate connections between nonhomologous chromosome regions.

Meiotic homologous chromosomes synapse and undergo crossing over (CO). In many eukaryotes, both synapsis and crossing over require the induction of double stranded breaks (DSBs) and subsequent repair via homologous recombination. In these organisms, two key proteins are recombinases RAD51 and DMC1.

A novel method to follow meiotic progression in Arabidopsis using confocal microscopy and 5-ethynyl-2'-deoxyuridine labeling.

Background: Meiosis progression in the more recent past has been investigated using 5-bromo-2'-deoxyuridine (BrdU) uptake by S-phase meiocytes undergoing DNA replication. BrdU uptake is detected by reaction with BrdU antibody followed by epifluorescent microscopy examination of chromosome spreads and/or squashes. We here report using confocal microscopic examination of intact meiocytes in conjunction with the new thymidine analog 5-ethynyl-2'-deoxyuridine (EdU).

Transmission electron microscopy and serial reconstructions reveal novel meiotic phenotypes for the ahp2 mutant of Arabidopsis thaliana.

We have found novel phenotypes for the previously studied Arabidopsis thaliana (L.) Heynh. meiotic mutant ahp2.

Chromosome fragile sites in Arabidopsis harbor matrix attachment regions that may be associated with ancestral chromosome rearrangement events.

Mutations in the BREVIPEDICELLUS (BP) gene of Arabidopsis thaliana condition a pleiotropic phenotype featuring defects in internode elongation, the homeotic conversion of internode to node tissue, and downward pointing flowers and pedicels. We have characterized five mutant alleles of BP, generated by EMS, fast neutrons, x-rays, and aberrant T-DNA insertion events. Curiously, all of these mutagens resulted in large deletions that range from 140 kbp to over 900 kbp just south of the centromere of chromosome 4.

Analysis of substage associations in prophase I of meiosis in floral buds of wild-type Arabidopsis thaliana (Brassicaceae).

We developed an improved cytological protocol for producing high quality, light microscope images of plant meiotic chromosomes. Because the technique works on species with small genomes and thick microsporocyte cell walls, it should be useful for studying the wild relatives of Arabidopsis and other eudicots with small genomes. Combining this improved fixation protocol with our new analysis of associated substages in floral buds, we can unambiguously assign individual meiotic cells to particular substages of prophase I in Arabidopsis thaliana, even for difficult distinctions such as that between late zygotene or early diplotene.

Disruption of the Arabidopsis SMC4 gene, AtCAP-C, compromises gametogenesis and embryogenesis.

In higher eukaryotes, the condensin complex is a multisubunit apparatus that plays a pivotal role in the coordinated condensation of chromatin during mitosis. The catalytic subunits, CAP-E and CAP-C, members of the SMC family of ATPases, form a heterodimer, the activity of which is controlled by the non-SMC subunits CAP-D2, CAP-G and CAP-H. Here, we report the characterization of a T-DNA insertion mutant of the Arabidopsis CAP-C gene.

Mutations in Arabidopsis condensin genes disrupt embryogenesis, meristem organization and segregation of homologous chromosomes during meiosis.

Proper chromatin condensation and sister chromatid resolution are essential for the maintenance of chromosomal integrity during cell division, and is in part mediated by a conserved multisubunit apparatus termed the condensin complex. The core subunits of the complex are members of the SMC2 (Structural Maintenance of Chromosomes) and SMC4 gene families. We have cloned an Arabidopsis gene, AtCAP-E1, which is a functional ortholog of the yeast SMC2 gene.

Dmc1 fluorescent foci in prophase I nuclei of diploid, triploid and hybrid lilies.

We examined the distribution of meiotic epitopes for the Dmc1 protein of lilies in a normal diploid, a triploid, and in a diploid species-hybrid. The triploid has an extra chromosome set; all three sets align, but only two of the three axes intimately pair at a given location. Our findings with the triploid support the idea that retention of the foci until the pachytene stage requires a successful homology check and synaptonemal complex (SC) initiation; the number of foci in the triploid diminishes by approximately 30% from early zygotene to pachytene, and the triploid pachytene values are similar to the pachytene values of the diploid.