From Microscopy to Nanoscopy: Defining an Meiotic Atlas at the Nanometer Scale.

Visualization of meiotic chromosomes and the proteins involved in meiotic recombination have become essential to study meiosis in many systems including the model plant . Recent advances in super-resolution technologies changed how microscopic images are acquired and analyzed. New technologies enable observation of cells and nuclei at a nanometer scale and hold great promise to the field since they allow observing complex meiotic molecular processes with unprecedented detail.

ATM controls meiotic DNA double-strand break formation and recombination and affects synaptonemal complex organization in plants.

Meiosis is a specialized cell division that gives rise to genetically distinct gametic cells. Meiosis relies on the tightly controlled formation of DNA double-strand breaks (DSBs) and their repair via homologous recombination for correct chromosome segregation. Like all forms of DNA damage, meiotic DSBs are potentially harmful and their formation activates an elaborate response to inhibit excessive DNA break formation and ensure successful repair.

Targeted Analysis of Chromatin Events (TACE).

Visualization of meiotic chromatin from pollen mother cells has become an essential technique to study meiosis in the model plant Arabidopsis thaliana. Here we present an advanced cytogenetic method that combines improved immunocytology with chromosome painting, thereby generating a tool to quantitatively analyze localization of proteins to any given genomic region. Proteins involved in different processes such as DNA double-strand break formation and recombinational repair can be visualized on meiotic chromatin with the additional feature of assessing their abundance at specific chromosomal locations.

FANCD2 Promotes Meiotic Crossover Formation.

Fanconi anemia (FA) is a human autosomal recessive disorder characterized by chromosomal instability, developmental pathologies, predisposition to cancer, and reduced fertility. So far, 19 genes have been implicated in FA, most of them involved in DNA repair. Some are conserved across higher eukaryotes, including plants.

Compartmentalization of DNA Damage Response between Heterochromatin and Euchromatin Is Mediated by Distinct H2A Histone Variants.

DNA double-strand break (DSB) repair depends on the ataxia telangiectasia mutated (ATM) kinase that phosphorylates the conserved C-terminal SQ motif present in the histone variant H2A.X [1-7]. In constitutive heterochromatin of mammals, DSB repair is delayed and relies on phosphorylation of the proteins HP1 and KAP1 by ATM [2, 8-14].

The recombinases DMC1 and RAD51 are functionally and spatially separated during meiosis in Arabidopsis.

Meiosis ensures the reduction of the genome before the formation of generative cells and promotes the exchange of genetic information between homologous chromosomes by recombination. Essential for these events are programmed DNA double strand breaks (DSBs) providing single-stranded DNA overhangs after their processing. These overhangs, together with the RADiation sensitive51 (RAD51) and DMC1 Disrupted Meiotic cDNA1 (DMC1) recombinases, mediate the search for homologous sequences.

Retinoblastoma protein goes green: the role of RBR in Arabidopsis meiosis.

This issue of features an article by Chen highlighting a novel function of the plant retinoblastoma protein in meiosis.