The Opposing Actions of Arabidopsis CHROMOSOME TRANSMISSION FIDELITY7 and WINGS APART-LIKE1 and 2 Differ in Mitotic and Meiotic Cells

Abstract

Sister chromatid cohesion, which is mediated by the cohesin complex, is essential for the proper segregation of chromosomes during mitosis and meiosis. Stable binding of cohesin with chromosomes is regulated in part by the opposing actions of CTF7 (CHROMOSOME TRANSMISSION FIDELITY7) and WAPL (WINGS APART-LIKE). In this study, we characterized the interaction between Arabidopsis thaliana CTF7 and WAPL by conducting a detailed analysis of wapl1-1 wapl2 ctf7 plants. ctf7 plants exhibit major defects in vegetative growth and development and are completely sterile. Inactivation of WAPL restores normal growth, mitosis, and some fertility to ctf7 plants. This shows that the CTF7/WAPL cohesin system is not essential for mitosis in vegetative cells and suggests that plants may contain a second mechanism to regulate mitotic cohesin. WAPL inactivation restores cohesin binding and suppresses ctf7-associated meiotic cohesion defects, demonstrating that WAPL and CTF7 function as antagonists to regulate meiotic sister chromatid cohesion. The ctf7 mutation only had a minor effect on wapl-associated defects in chromosome condensation and centromere association. These results demonstrate that WAPL has additional roles that are independent of its role in regulating chromatin-bound cohesin.

In Favor of Establishment: Regulation of Chromatid Cohesion in Plants

“…Immunolocalization of SYN1 in meiocytes confirmed that the release of cohesin during diakinesis is recovered in wapl1 wapl2 ctf7 triple homozygous mutant plants ( De et al, 2016 ). However, comet assay experiments in vegetative tissues revealed that both WAPL1/2 and ECO1/CTF7 are important for the repair of DNA DSBs during the cell cycle in Arabidopsis ( De et al, 2016 ). In addition, flow cytometry revealed a high level of aneuploidy in vegetative tissues of the triple mutant ( De et al, 2016 ).…”

“…Hence, Arabidopsis WAPL genes may play a critical role during meiosis, and mechanisms involved in the removal of cohesin during prophase may vary between mitosis and meiosis in plants. Additionally, inactivation of the two Arabidopsis WAPL genes can suppress the lethal phenotype produced by the lack of CTF7 ( De et al, 2016 ) and allows for normal vegetative growth and production of a reduced number of viable seeds ( De et al, 2016 ). Immunolocalization of SYN1 in meiocytes confirmed that the release of cohesin during diakinesis is recovered in wapl1 wapl2 ctf7 triple homozygous mutant plants ( De et al, 2016 ).…”

“…Additionally, inactivation of the two Arabidopsis WAPL genes can suppress the lethal phenotype produced by the lack of CTF7 ( De et al, 2016 ) and allows for normal vegetative growth and production of a reduced number of viable seeds ( De et al, 2016 ). Immunolocalization of SYN1 in meiocytes confirmed that the release of cohesin during diakinesis is recovered in wapl1 wapl2 ctf7 triple homozygous mutant plants ( De et al, 2016 ). However, comet assay experiments in vegetative tissues revealed that both WAPL1/2 and ECO1/CTF7 are important for the repair of DNA DSBs during the cell cycle in Arabidopsis ( De et al, 2016 ).…”

“…However, comet assay experiments in vegetative tissues revealed that both WAPL1/2 and ECO1/CTF7 are important for the repair of DNA DSBs during the cell cycle in Arabidopsis ( De et al, 2016 ). In addition, flow cytometry revealed a high level of aneuploidy in vegetative tissues of the triple mutant ( De et al, 2016 ). All these results demonstrate that WAPL1/2 is important for the timely release of cohesion during meiosis and that inactivation of WAPL1/2 most-likely abrogates the requirement for SMC3 acetylation by CTF7 during mitosis ( De et al, 2016 ).…”

“…In addition, flow cytometry revealed a high level of aneuploidy in vegetative tissues of the triple mutant ( De et al, 2016 ). All these results demonstrate that WAPL1/2 is important for the timely release of cohesion during meiosis and that inactivation of WAPL1/2 most-likely abrogates the requirement for SMC3 acetylation by CTF7 during mitosis ( De et al, 2016 ). These plants are still able to develop and reproduce, which suggests the presence of an alternative cohesion pathway that awaits proper identification and functional characterization.…”