The STRUCTURAL MAINTENANCE OF CHROMOSOMES 5/6 Complex Promotes Sister Chromatid Alignment and Homologous Recombination after DNA Damage inArabidopsis thaliana   

Abstract

Sister chromatids are often arranged as incompletely aligned entities in interphase nuclei of Arabidopsis thaliana. The STRUCTURAL MAINTENANCE OF CHROMOSOMES (SMC) 5/6 complex, together with cohesin, is involved in double-strand break (DSB) repair by sister chromatid recombination in yeasts and mammals. Here, we analyzed the function of genes in Arabidopsis. The wild-type allele of SMC5 is essential for seed development. Each of the two SMC6 homologs of Arabidopsis is required for efficient repair of DNA breakage via intermolecular homologous recombination in somatic cells. Alignment of sister chromatids is enhanced transiently after X-irradiation (and mitomycin C treatment) in wild-type nuclei. In the smc5/6 mutants, the x-ray-mediated increase in sister chromatid alignment is much lower and delayed. The reduced S phase-established cohesion caused by a knockout mutation in one of the a-kleisin genes, SYN1, also perturbed enhancement of sister chromatid alignment after irradiation, suggesting that the S phase-established cohesion is a prerequisite for correct DSB-dependent cohesion. The radiation-sensitive51 mutant, deficient in heteroduplex formation during DSB repair, showed wild-type frequencies of sister chromatid alignment after X-irradiation, implying that the irradiation-mediated increase in sister chromatid alignment is a prerequisite for, rather than a consequence of, DNA strand exchange between sister chromatids. Our results suggest that the SMC5/6 complex promotes sister chromatid cohesion after DNA breakage and facilitates homologous recombination between sister chromatids.

AtMMS21, an SMC5/6 Complex Subunit, Is Involved in Stem Cell Niche Maintenance and DNA Damage Responses in Arabidopsis Roots

“…Recently, a similar SMC5/6 complex, which also acts in DNA repair, was reported in plant cells (Watanabe et al, 2009). However, non-SMC components of this complex have not been characterized in terms of their interactions with the SMC5/6 complex.…”

“…A previous study showed that heterozygotes for a transferred DNA insertion in the Arabidopsis SMC5 gene did not yield homozygous mutants and that siliques of heterozygous plants contained 25% shrunken seeds, indicating that SMC5 is essential for seed development (Watanabe et al, 2009). These findings prompted us to speculate that SMC5 might function in embryogenesis.…”

MGO3 and GIP1 act synergistically for the maintenance of centromeric cohesion

“…4 Similarly, mutations in the structural maintenance of chromosome 5/6 complex (SMC5/6) lead to defects in sister chromosome cohesion as well as impaired DNA repair in Arabidopsis. 27 All these data argue for a tight control between DNA replication, DNA repair and sister chromatid cohesion. As postreplicative DNA repair is impaired in bru1, 12 we need to further investigate this aspect in relation with GIPs and the nuclear periphery.…”

Involvement of AtPolλ in the Repair of High Salt- and DNA Cross-Linking Agent-Induced Double Strand Breaks in Arabidopsis

“…Representative gel images from at least three independent trials are shown for A, B, D, E, and F. A 1.59-kb AtPoll cDNA fragment was used as a probe in DNA and RNA gel blotting. (Dmitrieva and Burg, 2005;Watanabe et al, 2009). Therefore, we next specifically examined the induction pattern of AtPoll message levels, particularly in response to high salinity and MMC treatments, in 7-dold wild-type Arabidopsis seedlings.…”