AUTHOR=Bazile Jeanne , Nadaud Isabelle , Lasserre-Zuber Pauline , Kitt Jonathan , De Oliveira Romain , Choulet Frédéric , Sourdille Pierre 

TITLE=TaRECQ4 contributes to maintain both homologous and homoeologous recombination during wheat meiosis

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1342976

DOI=10.3389/fpls.2023.1342976

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p>Meiotic recombination (or crossover, CO) is essential for gamete fertility as well as for alleles and genes reshuffling that is at the heart of plant breeding. However, CO remains a limited event, which strongly hampers the rapid production of original and improved cultivars. <italic>RecQ4</italic> is a gene encoding a helicase protein that, when mutated, contributes to improve recombination rate in all species where it has been evaluated so far. </p></sec><sec><title>Methods</title><p>In this study, we developed wheat (<italic>Triticum aestivum</italic> L.) triple mutant (TM) for the three homoeologous copies of <italic>TaRecQ4</italic> as well as mutants for two copies and heterozygous for the last one (Htz-A, Htz-B, Htz-D).</p></sec><sec><title>Results</title><p>Phenotypic observation revealed a significant reduction of fertility and pollen viability in TM and Htz-B plants compared to wild type plants suggesting major defects during meiosis. Cytogenetic analyses of these plants showed that complete absence of <italic>TaRecQ4</italic> as observed in TM plants, leads to chromosome fragmentation during the pachytene stage, resulting in problems in the segregation of chromosomes during meiosis. Htz-A and Htz-D mutants had an almost normal meiotic progression indicating that both <italic>TaRecQ4-A</italic> and <italic>TaRecQ4-D</italic> copies are functional and that there is no dosage effect for <italic>TaRecQ4</italic> in bread wheat. On the contrary, the <italic>TaRecQ4-B</italic> copy seems knocked-out, probably because of a SNP leading to a Threonine&gt;Alanine change at position 539 (T539A) of the protein, that occurs in the crucial helicase ATP bind/DEAD/ResIII domain which unwinds nucleic acids. Occurrence of numerous multivalents in TM plants suggests that <italic>TaRecQ4</italic> could also play a role in the control of homoeologous recombination. </p></sec><sec><title>Discussion</title><p>These findings provide a foundation for further molecular investigations into wheat meiosis regulation to fully understand the underlying mechanisms of how <italic>TaRecQ4</italic> affects chiasma formation, as well as to identify ways to mitigate these defects and enhance both homologous and homoeologous recombination efficiency in wheat.</p></sec>