Background Pairing of homologous chromosomes at meiosis is an important requirement
Background Pairing of homologous chromosomes at meiosis is an important requirement for recombination and balanced chromosome segregation among the products of meiotic division. 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. Conclusion We conclude that AtMND1 is usually 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. Background The formation of at least one crossover between pairs of homologous chromosomes is necessary for their correct segregation at meiosis I. The stages of interactions between homologous chromosomes that lead to crossover formation have been broadly grouped as: an initial localization of homologous chromosomes within the same region, mediated by interstitial interactions; close pairing and strand exchange at the DNA level as a part of recombination; and synapsis between homologous chromosomes together with completion 1193383-09-3 IC50 of recombination . Recombination at the DNA level in yeast and in other organisms is initiated by double strand breaks (DSBs) made by Spo11 [2,3]. Conversation between DSBs and a homologous intact chromosome can lead to crossover and noncrossover recombination products which are created by two different pathways . Processing of DSBs by 5′ end resection yields 3′ single-stranded ends that asymmetrically invade a homologous chromosome and lead to the formation of a double-Holliday junction intermediate which has been proposed to account for the majority of crossovers [5,6]. Conversation between homologous chromosomes at the sites of DSBs is usually promoted by the action of the RecA-like strand exchange proteins Rad51 and Dmc1 [7,8]. Several lines of evidence suggest that Rad51 and Dmc1 have different but overlapping functions [9,10] and interact with unique units of proteins in promoting recombination [11-13]. Rad51 acts in mitosis and in meiosis  whereas Dmc1 is usually meiosis specific . MND1 was recognized in Saccharomyces cerevisiae using three different screens based on genetic and functional genomic approaches that were directed at identifying genes that played a role in meiotic recombination and/or chromosome segregation [16-18]. The mnd1 mutant shows defects in nuclear division, meiotic recombination, and repair of DSBs. Mnd1 has been shown to act as a complex with Hop2 [18,19] and the Mnd1/Hop2 complex 1193383-09-3 IC50 localizes to chromosomes independently of Rad51 and Dmc1 [18,20]. Genetic studies have provided evidence that Hop2 and Mnd1 take action in the same pathway as Dmc1 and Rad51 [17-21]. Biochemical studies using yeast, 1193383-09-3 IC50 human, and mouse orthologues have provided evidence that Mnd1/Hop2 stimulates the strand exchange activity of Dmc1 and that of Rad51 [19,22,23]. The conversation of Mnd1 with Hop2 has been shown to promote the conversation of Hop2 with Dmc1 and stimulate the strand exchange activity of Dmc1 . Additional roles for Rabbit polyclonal to ADORA3 Mnd1/Hop2 that have been proposed are in promoting interhomologue associations at DSBs through conversation with the axial elements or other proteins perhaps by relieving structural constraints [18,20,25] and in the designation of DSBs for noncrossover recombination . Orthologues of MND1 have been recognized in protists, fungi, plants, and animals and some of these have been characterized and shown to have closely related functions . In yeast an mnd1 disruption has been reported to cause defects only in meiosis and does not result in sensitivity to radiation induced DNA damage . However, an Arabidopsis mutant, Atmnd1-1 has been recently shown to be sensitive to gamma radiation indicative of a role in mitotic repair, and also to undergo chromosome fragmentation during meiosis . Here we have used the same mutant allele to analyze the role of the AtMND1 gene in meiosis. We show that AtMND1 1193383-09-3 IC50 is usually 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. We also show that consistent with its role in meiosis, AtMND1 is usually strongly expressed in meiocytes. Results AtMND1 shows increased expression in reproductive tissues The Arabidopsis genome contains a single orthologue of MND1 (AtMND1) corresponding to the annotated gene ID No. At4g29170 and supported by a cDNA (Accession No. “type”:”entrez-nucleotide”,”attrs”:”text”:”AA063855″,”term_id”:”1557846″,”term_text”:”AA063855″AA063855). The encoded protein shows 26% identity (47% similarity) to Mnd1 and is 230 aa in length which is close to that of Mnd1 (219 aa). Expression of AtMND1 was compared between rosette.