SCEP1 and SCEP2 are two novel components of the Synaptonemal Complex in Arabidopsis thaliana

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Vrielynck, Nathalie | Peuch, Marion | Chambon, Aurélie | Grelon, Mathilde | Mézard, Christine

Edité par CCSD -

International audience. The synaptonemal complex (SC) is a proteinaceous zipper-like structure that links the homologous chromosomes over their entire length. The ultrastucture of the SC is highly conserved in most eukaryotes but SC components do not show any sequence similarity between organisms. In Arabidopsis thaliana, transverse filaments are made by the 2 redundant proteins ZYP1a and ZYP1b but none of the central element proteins have been identified yet compared to 5 central element proteins that have been characterized in mice and C. elegans and 2 in S. cerevisiae. Based on transcriptomic data, we identified a series of uncharacterized genes, inactivation of which display meiotic CO defects, including SCEP1 and SCEP2. We found that (i) in absence of SCEP1 or SCEP2, chromosomes associate but do not synapse and ZYP1 is not detected (ii) SCEP1 colocalizes with ZYP1 in male meiosis (iii) in zyp1ab mutants, SCEP1 is not detected (iv) SCEP1 and SCEP2 are predicted by alphafold to fold as small coiled-coiled protein and to form a complex; we confirmed that they interact by yeast two hybrids (v) in absence of SCEP1 or SCEP2, MLH1 foci are increased by 50% as in zyp1ab mutants. All these data suggest that SCEP1 and SCEP2 belong to the SC central element.

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