SCEP1 and SCEP2 are essential for meiosis in Arabidopsis thaliana

Meiosis is at the heart of sexual reproduction in eukaryotes. It leads to the formation of gametes, which carry half of an individual's genetic information in the form of chromosomes. The male and female gametes then fuse during fertilization to create a new individual. During meiosis, pairs of chromosomes form "crossovers", exchanging chromosome fragments with one another, which are essential if each gamete is to receive one copy of each chromosome. These crossovers are a source of genetic diversity that is crucial to the creation of new varieties. The number and position of these crossovers are regulated by a set of proteins, some of which form a structure called the synaptonemal complex. The aim of this work was to gain a better understanding of the architecture and role of the synaptonemal complex. Very few proteins belonging to the synaptonemal complex had been identified in plants.

In this work, two new small proteins called SCEP1 and SCEP2 were identified and characterized. The structural predictions obtained with Alphafold suggest that these two proteins form a complex that has been detected at the center of the synaptonemal complex in the Arabidopsis thaliana plant. When SCEP1 and/or SCEP2 are not expressed, the synaptonemal complex is no longer formed, there are more crossovers per chromosome pair but some chromosomes do not receive crossovers, resulting in defects in gamete formation and a drop in plant fertility. These two proteins therefore play a central role in meiosis, and therefore in sexual reproduction.

Proteins similar to SCEP1 and SCEP2 have been found and predicted to form a structural complex similar to that of the Arabidopsis proteins in the majority of representative flowering plant species.