title: Cytological analysis of MRE11 protein during early meiotic prophase I in Arabidopsis and tomato.
abstract: Early recombination nodules (ENs) are multiprotein complexes that are thought to be involved in synapsis and recombination, but little is known about their components or how they may be involved in these events. In this study, we describe the cytological behavior of a possible EN component, MRE11, a protein that is important for the repair of the numerous, programmed deoxyribonucleic acid double-strand breaks (DSBs) that occur early in the meiotic prophase. By immunofluorescence, many MRE11 foci were associated with chromosomal axes during early prophase I in both wild-type Arabidopsis and tomato primary microsporocytes. Similar patterns of MRE11 foci were observed in two Arabidopsis mutants (Atspo11-1 and Atprd1) that are defective in DSB formation and synapsis. In tomato chromosomes, MRE11 foci were more common in distal euchromatin than in proximal heterochromatin, consistent with known EN patterns. However, electron microscopic immunogold localization demonstrated that only about 10% of ENs were labeled, and most MRE11 label was associated with synaptonemal complex components. Thus, in plants, MRE11 foci are not dependent on DSB formation, and most MRE11 foci do not correspond to ENs. More generally, our results show that the simple presence of large numbers of fluorescent foci associated with synapsing chromosomes is insufficient evidence to equate these foci with ENs.
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Leslie D
authors.initials: LD
authors.lastname: Lohmiller
authors.forename: Arnaud
authors.initials: A
authors.lastname: De Muyt
authors.forename: Brittany
authors.initials: B
authors.lastname: Howard
authors.forename: Hildo H
authors.initials: HH
authors.lastname: Offenberg
authors.forename: Christa
authors.initials: C
authors.lastname: Heyting
authors.forename: Mathilde
authors.initials: M
authors.lastname: Grelon
authors.forename: Lorinda K
authors.initials: LK
authors.lastname: Anderson
mesh_terms: D017360:Arabidopsis / Q000166:cytology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D018551:Solanum lycopersicum / Q000166:cytology*; D000076228:MRE11 Homologue Protein; D049469:Meiotic Prophase I; D009154:Mutation / Q000235:genetics; D021381:Protein Transport; D011995:Recombination, Genetic / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D013573:Synaptonemal Complex / Q000648:ultrastructure; D016615:Telomere / Q000378:metabolism; D000098550:Structural Maintenance of Chromosome Protein 1
chemical_list: C411742:ASY1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C492900:Mre11 protein, Arabidopsis; D000098550:Structural Maintenance of Chromosome Protein 1; D000076228:MRE11 Homologue Protein; D003850:Deoxyribonuclease I