SWITCH1 (SWI1): a novel protein required for the establishment of sister chromatid cohesion and for bivalent formation at meiosis.
We have characterized a new gene, SWI1, involved in sister chromatid cohesion during both male and female meiosis in Arabidopsis thaliana. A first allele, swi1.1, was obtained as a T-DNA tagged mutant and was described previously as abnormal exclusively in female meiosis. We have isolated a new allele, swi1.2, which is defective for both male and female meiosis. In swi1.2 male meiosis, the classical steps of prophase were not observed, especially because homologs do not synapse. Chromatid arms and centromeres lost their cohesion in a stepwise manner before metaphase I, and 20 chromatids instead of five bivalents were seen at the metaphase plate, which was followed by an aberrant segregation. In contrast, swi1.2 female meiocytes performed a mitotic-like division instead of meiosis, indicating a distinct role for SWI1 or a different effect of the loss of SWI1 function in both processes. The SWI1 gene was cloned; the putative SWI1 protein did not show strong similarity to any known protein. Plants transformed with a SWI1-GFP fusion indicated that SWI1 protein is present in meiocyte nuclei, before meiosis and at a very early stage of prophase. Thus, SWI1 appears to be a novel protein involved in chromatid cohesion establishment and in chromosome structure during meiosis, but with clear differences between male and female meiosis.
Mercier
R
R
Station de Génétique et d'Amélioration des Plantes, Institut National de la Recherche Agronomique, Route de Saint-Cyr, 78026 Versailles cedex, France. rmercier@versailles.inra.fr
Vezon
D
D
Bullier
E
E
Motamayor
J C
JC
Sellier
A
A
Lefèvre
F
F
Pelletier
G
G
Horlow
C
C
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D002503:Centromere; D002842:Chromatids / Q000502:physiology* / Q000648:ultrastructure; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D005718:Gametogenesis; D008540:Meiosis / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010940:Plant Proteins / Q000235:genetics
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D009687:Nuclear Proteins; D010940:Plant Proteins; C513099:SWI1 protein, Arabidopsis