Biology subjects

Colas, I.

Publications and source records attributed to Colas, I..

3 recordsLinked to original sources

bioRxiv2023

The RAD51 paralogue HvXRCC2 regulates meiosis and recombination in barley

Using a positional candidate-gene approach we show that semi-sterile desynaptic8 mutants are associated with deletions in or complete knockout of the barley homolog of XRCC2 (X-Ray Repair Cross Complementing 2). In barley XRCC2 mutants, the initial meiotic progression is normal, albeit with a small delay in initiation, with completion of synapsis. However, the absence of HvXRCC2 subsequently leads to a dramatic reduction in the number of crossovers, chromosome mis-segregation, and infertility, suggesting that HvXRCC2 plays a major role in recombination. This mutant phenotype is congruent with that reported in mammalian studies but contrasts with the XRCC2 mutant in Arabidopsis which is fertile, exhibits normal chromosome pairing and correct chromosome segregation, and is associated with an increased rate of crossovers. This indicates that the XRCC2 mutant phenotype in Arabidopsis is not representative of all plants and that XRCC2 is not a good candidate for the modulation of recombination in barley. HighlightThe mutants of the barley homolog of XRCC2 exhibit delays in replication leading to defective meiosis, altered RAD51 orthologue behaviour, and significant reduction in the number of crossovers as in canonical mammalian XRCC2 mutants but unlike those in Arabidopsis.

plant biology↗

bioRxiv2023

Loss of E3 ligase HvST1 function substantially increases recombination

During meiosis, genetic recombination occurs via repair of DNA double-strand breaks (DSBs) as crossovers (COs) resulting in the exchange of parental genetic material (De Muyt et al., 2009). Crossovers are important for chromosome segregation and shuffling genetic variation, but their number and distribution are tightly regulated (Zickler and Kleckner, 2015). In barley and other large genome cereals, recombination events are limited in number and mainly restricted to the ends of chromosomes (Mascher et al., 2017), constraining progress in plant breeding. Recent studies have highlighted subtle differences in meiotic progression (Higgins et al., 2012; Phillips et al., 2013) and the distribution of recombination events in barley compared to other plants (Colas et al., 2016; Colas et al., 2017; Colas et al 2019), indicating possible evolutionary divergence of the meiotic program in large genome crops. Here we identify a spontaneous loss of function mutation in the grass specific E3 ubiquitin ligase HvST1 (Sticky Telomeres 1) which results in semi-sterility in barley. We show that abnormal synapsis in the absence of HvST1 function increases overall recombination by up to 2.5-fold and that HvST1 is capable of ubiquitinating ASY1, a key component of the lateral elements of the synaptonemal complex. Our findings shed light on an evolutionarily divergent pathway regulating synapsis and recombination in cereals. This natural loss of function variant presents new opportunities for the modulation of recombination in large genome cereals.

plant biology↗

bioRxiv2020

Time-resolved transcriptome of barley anthers and meiocytes reveals robust and largely stable gene expression changes at meiosis entry

In flowering plants, successful germinal cell development and meiotic recombination depend upon a combination of environmental and genetic factors. To gain insights into this specialised reproductive development programme we used short- and long-read RNA-sequencing (RNA-seq) to study the temporal dynamics of transcript abundance in immuno-cytologically staged barley (Hordeum vulgare) anthers and meiocytes. We show that the most significant transcriptional changes occur at the transition from pre-meiosis to leptotene-zygotene, which is followed by largely stable transcript abundance throughout prophase I. Our analysis reveals that the developing anthers and meiocytes are enriched in long non-coding RNAs (lncRNAs) and that entry to meiosis is characterized by their robust and significant down regulation. Intriguingly, only 24% of a collection of putative meiotic gene orthologues showed differential transcript abundance in at least one stage or tissue comparison. Changes in the abundance of numerous transcription factors, representatives of the small RNA processing machinery, and post-translational modification pathways highlight the complexity of the regulatory networks involved. These developmental, time-resolved, and dynamic transcriptomes increase our understanding of anther and meiocyte development and will help guide future research. One sentence summaryAnalysis of RNA-seq data from meiotically staged barley anthers and meiocytes highlights the role of lncRNAs within a complex network of transcriptional and post-transcriptional regulation accompanied by a hiatus in differential gene expression during prophase I. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Robbie Waugh (robbie.waugh@hutton.ac.uk)

developmental biology↗