Pathways to meiotic recombination in Arabidopsis thaliana.

CONTENTS: Summary 1 I. Introduction 2 II. The meiotic pathway: a brief overview 2 III. Homologous chromosome pairing and  movement during prophase I 3 IV. Meiotic DNA double-strand break formation 4 V. Processing of DNA double-strand breaks 6 VI. Strand exchange: the role of the RecA  homologues and their accessory proteins 7 VII. Promotion of stable strand exchange 10 VIII. Pathways to crossover formation 10 IX. The class I pathway of meiotic recombination 11 X. The class II pathway of meiotic recombination 14 XI. Holliday junction (Hj) resolution 15 XII. Noncrossover pathways and the crossover/ noncrossover decision 15 XIII. Conclusions 16 Acknowledgements 16 References 16 SUMMARY: Meiosis is a central feature of sexual reproduction. Studies in plants have made and continue to make an important contribution to fundamental research aimed at the understanding of this complex process. Moreover, homologous recombination during meiosis provides the basis for plant breeders to create new varieties of crops. The increasing global demand for food, combined with the challenges from climate change, will require sustained efforts in crop improvement. An understanding of the factors that control meiotic recombination has the potential to make an important contribution to this challenge by providing the breeder with the means to make fuller use of the genetic variability that is available within crop species. Cytogenetic studies in plants have provided considerable insights into chromosome organization and behaviour during meiosis. More recently, studies, predominantly in Arabidopsis thaliana, are providing important insights into the genes and proteins that are required for crossover formation during plant meiosis. As a result, substantial progress in the understanding of the molecular mechanisms that underpin meiosis in plants has begun to emerge. This article summarizes current progress in the understanding of meiotic recombination and its control in Arabidopsis. We also assess the relationship between meiotic recombination in Arabidopsis and other eukaryotes, highlighting areas of close similarity and apparent differences.