Downregulation of Barley Regulator of Telomere Elongation Helicase 1 Alters the Distribution of Meiotic Crossovers.

Abdellah Barakate,Jamie Orr,Robbie Waugh,Sebastian Vivera,Jennifer Stephens,Diane Davidson,Luke Ramsay,Claire Halpin,Mikel Arrieta,Miriam Schreiber,Malcolm Macaulay

doi:10.3389/fpls.2021.745070

Abstract

Programmed meiotic DNA double-strand breaks (DSBs), necessary for proper chromosomal segregation and viable gamete formation, are repaired by homologous recombination (HR) as crossovers (COs) or non-crossovers (NCOs). The mechanisms regulating the number and distribution of COs are still poorly understood. The regulator of telomere elongation helicase 1 (RTEL1) DNA helicase was previously shown to enforce the number of meiotic COs in Caenorhabditis elegans but its function in plants has been studied only in the vegetative phase. Here, we characterised barley RTEL1 gene structure and expression using RNA-seq data previously obtained from vegetative and reproductive organs and tissues. Using RNAi, we downregulated RTEL1 expression specifically in reproductive tissues and analysed its impact on recombination using a barley 50k iSelect SNP Array. Unlike in C. elegans, in a population segregating for RTEL1 downregulated by RNAi, high resolution genome-wide genetic analysis revealed a significant increase of COs at distal chromosomal regions of barley without a change in their total number. Our data reveal the important role of RTEL1 helicase in plant meiosis and control of recombination.

Highlights

Meiosis is a specialised cell division that generates haploid gametes through genome duplication followed by two rounds of chromosome segregation
Barley regulator of telomere elongation helicase 1 (RTEL1)-specific primers were used in rapid amplification of cDNA ends (RACE) and reverse transcription PCR (RT-PCR) to clone the full-length cDNA of 3,370 bp (NCBI accession number: MW689197)
Meiotic recombination, which is necessary for proper chromosomal segregation, is tightly regulated by the intricate integration of programmed double-strand breaks (DSBs) induction, homologous recombination (HR) repair machinery and chromosomal remodelling resulting in the right proportions of CO and NCO recombinants (Altendorfer et al, 2020)

Summary

Introduction

Meiosis is a specialised cell division that generates haploid gametes through genome duplication followed by two rounds of chromosome segregation. At early prophase I, the homologs pair and synapse concomitantly with the introduction of a large number of DNA double-strand breaks (DSBs) by the topoisomerase type II-like protein Spo and its cofactors (Edlinger and Schlögelhofer, 2011; Panizza et al, 2011; Yadav and Bouuaert, 2021). The number of these programmed DSBs has been shown to be determined by the level of Spo activity (Xue et al, 2018) and restrained by the homolog engagement initiation during synaptonemal complex (SC) formation (Mu et al, 2020). In Arabidopsis, this topoisomerase was found to play a role in the resolution of meiotic chromosomal interlocks (Martinez-Garcia et al, 2018) whilst the CO interference is imposed by the SC (Capilla-Pérez et al, 2021; France et al, 2021)

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Conclusion