Homologous chromosome associations in domains before meiosis could facilitate chromosome recognition and pairing in wheat

Abstract

The increasing human population demands an increase in crop yields that must be implemented through breeding programmes to ensure a more efficient and sustainable production of agro-food products. In the framework of breeding, genetic crosses are developed between cultivated species such as wheat and their relative species that are used as genetic donors to transfer desirable agronomic traits into the crop. Unfortunately, interspecific associations between chromosomes from the donor species and the cultivar are rare during meiosis, the process to produce gametes in organisms with sexual reproduction, hampering the transfer of genetic variability into wheat. In addition, little is known about how homologous (equivalent) chromosomes initiate interaction and recognition within the cell nucleus to enter meiosis. In this context, we aim to get insight into wheat chromatin structure, particularly the distribution of homologous chromosomes within the cell nucleus and their putative interactions in premeiotic stages to facilitate chromosome associations and recombination at the beginning of meiosis. Cytogenetics allows the study of both the structure and the behaviour of chromosomes during meiosis and is key in plant breeding. In this study we visualized an extra pair of barley homologous chromosomes in a wheat genetic background to study the spatial distribution, arrangements and interactions occurring exclusively between this pair of homologous chromosomes during premeiosis using fluorescence in situ hybridization (FISH). Our results suggest that homologous chromosomes can initiate interactions in premeiotic stages that could facilitate the processes of specific chromosome recognition and association occurring at the onset of meiosis.

Incorrect recombination partner associations contribute to meiotic instability of neo‐allopolyploid Arabidopsis suecica

“…These initial contacts are thought to trigger chromosome movements that promote homology search and pairing of homologous chromosomes, which can then be stabilized by homologous recombination and synaptonemal complex assembly (Da Ines & White, 2015). In polyploid wheat and rice, centromeres associate and then form homologous pairs prior to the onset of meiosis suggesting that pre‐meiotic centromere associations could mediate the sorting of homologous and homoeologous chromosomes in these polyploids (Martinez‐Perez et al ., 1999, 2000, 2001; Prieto et al ., 2004; Barea et al ., 2022). In agreement with data as previously described (Comai et al ., 2003), we do not observe pre‐meiotic centromere association in allopolyploid A. suecica , but centromere dynamics comparable to diploid A. thaliana and Brachipodium distachyon , where centromeres cluster at the leptotene‐zygotene transition prior to chromosome arm synapsis (Fig.…”