Article
- The EMBO Journal (2006) 25, 1315 - 1323
- doi:10.1038/sj.emboj.7600992
Published online: 9 February 2006
Subject Categories:
Reduced meiotic crossovers and delayed prophase I progression in AtMLH3-deficient Arabidopsis
Neil Jacksona, Eugenio Sanchez-Morana, Ewen Buckling, Susan J Armstrong, Gareth H Jones and Frederick Christopher Hugh Franklin
- The School of Biosciences, University of Birmingham, Edgbaston, Birmingham, UK
Correspondence to:
Frederick Christopher Hugh Franklin, The School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. Tel.:+44 121 414 5910; Fax: +44 121 414 5925; E-mail: f.c.h.franklin@bham.ac.uk
aThese authors contributed equally to this work
Received 10 November 2005; Accepted 17 January 2006
Abstract
Characterization of AtMLH3, the Arabidopsis homologue of the prokaryotic MutL mismatch repair gene, reveals that it is expressed in reproductive tissue where it is required for normal levels of meiotic crossovers (COs). Immunocytological studies in an Atmlh3 mutant indicate that chromosome pairing and synapsis proceed with normal distribution of the early recombination pathway proteins. Localization of the MutS homologue AtMSH4 occurs, suggesting that double Holliday junctions (dHjs) are formed, but the MutL homologue AtMLH1, which forms a heterocomplex with AtMLH3, fails to localize normally. Loss of AtMLH3 results in an 
60% reduction in COs and is accompanied by a substantial delay of 25 h in prophase I progression. Analysis of the chiasma distribution in Atmlh3 suggests that dHj resolution can occur, but in contrast to wild type where most or all dHjs are directed to form COs the outcome is biased in favour of a non-CO outcome by a ratio of around 2 to 1. The data are compatible with a model whereby the MutL complex imposes a dHj conformation that ensures CO formation.
Keywords:
- Arabidopsis,
- meiosis,
- mismatch repair,
- recombination
