Abstract
BackgroundPairing of homologous chromosomes at meiosis is an important requirement for recombination and balanced chromosome segregation among the products of meiotic division. Recombination is initiated by double strand breaks (DSBs) made by Spo11 followed by interaction of DSB sites with a homologous chromosome. This interaction requires the strand exchange proteins Rad51 and Dmc1 that bind to single stranded regions created by resection of ends at the site of DSBs and promote interactions with uncut DNA on the homologous partner. Recombination is also considered to be dependent on factors that stabilize interactions between homologous chromosomes. In budding yeast Hop2 and Mnd1 act as a complex to promote homologous pairing and recombination in conjunction with Rad51 and Dmc1.ResultsWe have analyzed the function of the Arabidopsis orthologue of the budding yeast MND1 gene (AtMND1). Loss of AtMND1 did not affect normal vegetative development but caused fragmentation and missegregation of chromosomes in male and female meiosis, formation of inviable gametes, and sterility. Analysis of the Atmnd1 Atspo11-1 double mutant indicated that chromosome fragmentation in Atmnd1 was suppressed by loss of Atspo11-1. Fluorescence in situ hybridization (FISH) analysis showed that homologous pairing failed to occur and homologues remained apart throughout meiosis. AtMND1 showed strong expression in meiocytes as revealed by RNA in situs.ConclusionWe conclude that AtMND1 is required for homologous pairing and is likely to play a role in the repair of DNA double strand breaks during meiosis in Arabidopsis, thus showing conservation of function with that of MND1 during meiosis in yeast.
Highlights
Pairing of homologous chromosomes at meiosis is an important requirement for recombination and balanced chromosome segregation among the products of meiotic division
Interaction between homologous chromosomes at the sites of double strand breaks (DSBs) is promoted by the action of the RecA-like strand exchange proteins Rad51 and Dmc1 [7,8]
We show that AtMND1 is required for homologous pairing, an early step in the recombination process and that chromosome fragmentation in the Atmnd1 mutant is likely to be due to defective repair of meiotic DSBs
Summary
Pairing of homologous chromosomes at meiosis is an important requirement for recombination and balanced chromosome segregation among the products of meiotic division. Recombination is initiated by double strand breaks (DSBs) made by Spo followed by interaction of DSB sites with a homologous chromosome. This interaction requires the strand exchange proteins Rad and Dmc that bind to single stranded regions created by resection of ends at the site of DSBs and promote interactions with uncut DNA on the homologous partner. Interaction between DSBs and a homologous intact chromosome can lead to crossover and noncrossover recombination products which are formed by two different pathways [4]. Interaction between homologous chromosomes at the sites of DSBs is promoted by the action of the RecA-like strand exchange proteins Rad and Dmc1 [7,8]. Rad acts in mitosis and in meiosis [14] whereas Dmc is meiosis specific [15]
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