Chromosome pairing, synapsis, and DNA recombination are three key processes that occur during early meiosis. A previous study of Poor Homologous Synapsis 1 (PHS1) in maize suggested that PHS1 has a role in coordinating these three processes. Here we report the isolation of wheat (Triticum aestivum) PHS1 (TaPHS1), and its expression profile during and after meiosis. While the TaPHS1 protein has sequence similarity to other plant PHS1/PHS1-like proteins, it also possesses a unique region of oligopeptide repeat units. We show that TaPHS1 interacts with both single- and double-stranded DNA in vitro and provide evidence of the protein region that imparts the DNA-binding ability. Immunolocalisation data from assays conducted using antisera raised against TaPHS1 show that TaPHS1 associates with chromatin during early meiosis, with the signal persisting beyond chromosome synapsis. Furthermore, TaPHS1 does not appear to colocalise with the asynapsis protein (TaASY1) suggesting that these proteins are probably independently coordinated. Significantly, the data from the DNA-binding assays and 3-dimensional immunolocalisation of TaPHS1 during early meiosis indicates that TaPHS1 interacts with DNA, a function not previously observed in either the Arabidopsis or maize PHS1 homologues. As such, these results provide new insight into the function of PHS1 during early meiosis in bread wheat. 1. Introduction For the majority of sexually reproducing organisms, meiosis is a cellular process required for gamete formation and is composed of one round of DNA replication, followed by two rounds of chromosome division. During meiosis I, a reductional division event leads to the segregation of homologous chromosome pairs, while an equational division during meiosis II leads to the segregation of the sister chromatids. For the successful juxtaposition of homologous chromosomes, three key processes occur during prophase I, namely, pairing, synapsis, and recombination. Previous studies investigating the molecular mechanisms of homologous chromosome pairing have revealed complex interplay between these three tightly linked processes [1–5]. In allopolyploid organisms such as bread wheat (Triticum aestivum), correct alignment and pairing of homologous chromosomes are complicated by the presence of genetically similar genomes, known as homoeologous genomes. Although bread wheat possesses three homoeologous genomes (termed A, B, and D), meiosis proceeds as if the organism is a diploid, in that pairing only occurs between homologous chromosomes from the same genome ([6–9] and references
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