SCEP1 and SCEP2 are two new components of the synaptonemal complex central element

Area of Science:

• Plant biology
• Molecular genetics
• Cell biology

Background:

• The synaptonemal complex (SC) is a conserved meiotic structure essential for homologous chromosome pairing and recombination.
• While SC structure is known in mammals and fungi, central element proteins remain largely uncharacterized in plants.

Purpose of the Study:

• To identify and characterize novel central element proteins of the synaptonemal complex in Arabidopsis thaliana.
• To elucidate the roles of these proteins in meiotic chromosome synapsis, recombination, and interference.

Main Methods:

• Protein complex identification and localization studies using immunofluorescence.
• Analysis of meiotic phenotypes in knockout mutants (scep1, scep2) using microscopy and genetic assays.

Main Results:

• Two coiled-coil proteins, SCEP1 and SCEP2, were identified as forming a complex at the central region of the Arabidopsis SC.
• scep1 and scep2 mutants exhibit failed chromosome synapsis (lack of ZYP1 loading), increased crossovers, loss of interference, and reduced heterochiasmy.
• Homologues of SCEP1 and SCEP2 are present across major angiosperm clades.

Conclusions:

• SCEP1 and SCEP2 represent the first identified plant SC central elements, analogous to those in other eukaryotes.
• These proteins play critical roles in regulating SC formation, chromosome synapsis, and the distribution of meiotic crossovers in plants.