Owth. Wild-type and mre11 mutant seeds were germinated on MS agar plates. c) Comparison of siliques harvested from mature wild-type and mre11 mutants. The siliques in the mr11-4 and mre11-3 lines produced no seeds. mre11-2 siliques have been complete (normal seed set) and were indistinguishable from wild-type. atm-2 mutant plants are partially sterile.doi: ten.1371/journal.pone.0078760.gComparative analysis of meiosisTo investigate the origin with the sterility of mre11-4 7-Ethoxyresorufin Metabolic Enzyme/Protease mutants we analyzed meiosis in pollen mother cells (PMCs). In wildtype male meiocytes Cement Inhibitors products chromosomes progressively condense in the course of leptotene (Figure 5a), pair up in zygotene (Figure 5b) and synapse in pachytene (Figure 5c). Five bivalents come to be visible by way of diplotene (Figure 5d), totally condensed in diakinesis (Figure 5i) and line up in metaphase plate (Figure 5j). Homologous chromosomes move to opposing cellular poles through anaphase I (Figure 5k) and in telophase I two polar groups of chromosomes are observed (Figure 5l). During second meiotic division sister chromatids separate to finally give the 4 haploid microspores (Figure 5m-p). In mre11-4 mutants standard prophase was absent and each of the subsequent stages of meiosis have been severely impaired. Immediately after standard leptotene (Figure 5e), fragmented chromosome threads appeared at the mid-prophase stage that corresponds towards the wild-type zygotene-pachytene (Figure 5f). A common looped ribbon-like structure, normally present in wild-type pachytene,was in no way observed in mre11-4 mutants, suggesting a failure to synapse homologous chromosomes within the absence of MRE11 function. Chromosome fragmentation became additional visible as chromatin continued to condense inside the subsequent stages of post zygo-pachytene and varying sizes and numbers of chromosome fragments, but no common bivalents had been observed in all PMCs (Figures 5g-h). Second meiotic division was identified based on the appearance from the standard organellar band within the middle with the PMCs. In spite of severe chromosomal fragmentation, meiosis progressed into meiosis II (Figures five r-s) and completed with polyads, containing microspores with unequal amounts of DNA (Figure 5t). This phenotype is comparable with meiotic defects observed in mre11-3 mutants [35]. As opposed to mre11-4 mutant plants that are entirely sterile, homozygous mre11-2 mutants are completely fertile [21] and we did not detect any cytological abnormalities in meiosis (Figures 6 a-l). While mre11-2 mutants have phenotypically normal appearance, they may be still sensitive to DNA harm [21]PLOS One | plosone.orgFunction of MRE11 in Arabidopsis MeiosisFigure three. Genome instability in mitotic cells from mre11 mutants. Anaphase spreads were ready from pistils stained with 4′,6-diamidino-2-phenylindole (DAPI) and visualized by epifluorescence microscopy. a) Wild-type figure (upper left) show the phragmoplast, the cytoplasmic structure that types in the equator of the spindle immediately after the chromosomes have divided during the anaphase of plant mitosis. Genome instability manifested by chromosome fusions and chromosomal breaks is evident in mre11-4 and mre11-3 cells. Examples of mre11-4 anaphase with two bridges and acentric fragment lagging involving separating daughter nuclei are shown. Thick fragmented bridge was detected in mre11-3 cell. Scale bar indicates 2 m and serves all micrographs. b) Graphic representation recapitulating the spectrum of cytological abnormalities in mitotic cells from wild-type and mre11 flower buds. Chromosomal aberr.