Altered distribution of MLH1 foci is associated with changes in cohesins and chromosome axis compaction in an asynaptic mutant of tomato |
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Authors: | Huanyu Qiao Hildo H Offenberg Lorinda K Anderson |
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Institution: | (1) Department of Biology and Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523, USA;(2) Present address: Department of Microbiology, University of California, Davis, CA 95616, USA;(3) Johannes Poststraat 49, 5348, TL, Oss, The Netherlands; |
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Abstract: | In most multicellular eukaryotes, synapsis synaptonemal complex (SC) formation] between pairs of homologous chromosomes during
prophase I of meiosis is closely linked with crossing over. Asynaptic mutants in plants have reduced synapsis and increased
univalent frequency, often resulting in genetically unbalanced gametes and reduced fertility. Surprisingly, some asynaptic
mutants (like as1 in tomato) have wild-type or increased levels of crossing over. To investigate, we examined SC spreads from as1/as1 microsporocytes using both light and electron microscopic immunolocalization. We observed increased numbers of MLH1 foci
(a crossover marker) per unit length of SC in as1 mutants compared to wild-type. These changes are associated with reduced levels of detectable cohesin proteins in the axial
and lateral elements (AE/LEs) of SCs, and the AE/LEs of as1 mutants are also significantly longer than those of wild-type or another asynaptic mutant. These results indicate that chromosome
axis structure, synapsis, and crossover control are all closely linked in plants. |
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