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SRS2 is required for MUS81-dependent CO formation in zmm mutants
Valentine Petiot1, Floriane Chéron1, Charles I White1
1Institut Génétique Reproduction et Développement (iGReD), Université Clermont Auvergne, UMR 6293 CNRS, U1103 INSERM, Clermont-Ferrand, France.
Abstract:
Helicases are enzymes that use the energy derived from ATP hydrolysis to translocate along and unwind nucleic acids. Accordingly, helicases are instrumental in maintaining genomic integrity and ensuring genetic diversity. Srs2 is a multi-functional DNA helicase that dismantles Rad51 nucleofilaments and regulates DNA strand invasion to prevent excessive or inappropriate homologous recombination in yeast. Consistently, the deletion of Srs2 has significant consequences for the maintenance of genome integrity in mitotic cells. In contrast, its role in meiotic recombination remains less clear. We present here substantial evidence that SRS2 plays an important role in meiotic recombination in the model plant Arabidopsis thaliana. Arabidopsis srs2 mutants exhibit moderate defects in DNA damage-induced RAD51 focus formation, but SRS2 is dispensable for DNA repair and RAD51-dependent recombination in somatic cells. Meiotic progression and fertility appear unaffected in srs2 plants but, strikingly, the absence of SRS2 leads to increased genetic interference accompanied by increased numbers of Class I COs and a reduction in MUS81-dependent Class II COs. We propose that SRS2 plays a role in MUS81-mediated resolution of a subset of recombination intermediates into Class II CO. The absence of SRS2 would thus lead to the alternative channeling of these recombination intermediates into the Class I CO pathway, resulting in an increased proportion of Class I CO.
Insights
The SRS2 helicase regulates DNA recombination during meiosis in Arabidopsis. Its absence alters crossover patterns, favoring Class I over Class II crossovers, impacting genetic diversity.
Area of Science:
- Molecular Biology
- Genetics
- Plant Science
Background:
- Helicases utilize ATP hydrolysis to unwind nucleic acids, crucial for genomic integrity and diversity.
- Srs2 (Sensitivity to Radiation Sensitive 2) is a DNA helicase that disassembles Rad51 nucleofilaments, regulating homologous recombination in yeast.
- While Srs2's role in mitotic cells is established, its function in meiotic recombination is less understood.
Purpose of the Study:
- To investigate the role of the SRS2 helicase in meiotic recombination in the model plant Arabidopsis thaliana.
- To determine the impact of SRS2 absence on DNA repair, recombination pathways, and meiotic progression.
Main Methods:
- Analysis of Arabidopsis srs2 mutants.
- Assessment of DNA damage-induced RAD51 focus formation in somatic cells.
- Evaluation of meiotic progression, fertility, genetic interference, and crossover (CO) class distribution (Class I and Class II).
Main Results:
- Arabidopsis srs2 mutants showed moderate defects in DNA damage-induced RAD51 focus formation but were proficient in somatic DNA repair and recombination.
- Meiotic progression and fertility were unaffected in srs2 plants.
- SRS2 absence resulted in increased genetic interference, a higher proportion of Class I COs, and a reduction in MUS81-dependent Class II COs.
Conclusions:
- SRS2 plays a significant role in meiotic recombination in Arabidopsis.
- SRS2 is proposed to function in the MUS81-mediated resolution of specific recombination intermediates into Class II COs.
- The absence of SRS2 redirects these intermediates towards the Class I CO pathway, altering crossover distribution and potentially influencing genetic diversity.
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