The Fanconi Anemia Ortholog FANCM Ensures Ordered Homologous Recombination in Both Somatic and Meiotic Cells in Arabidopsis

Abstract

The human hereditary disease Fanconi anemia leads to severe symptoms, including developmental defects and breakdown of the hematopoietic system. It is caused by single mutations in the FANC genes, one of which encodes the DNA translocase FANCM (for Fanconi anemia complementation group M), which is required for the repair of DNA interstrand cross-links to ensure replication progression. We identified a homolog of FANCM in Arabidopsis thaliana that is not directly involved in the repair of DNA lesions but suppresses spontaneous somatic homologous recombination via a RecQ helicase (At-RECQ4A)-independent pathway. In addition, it is required for double-strand break-induced homologous recombination. The fertility of Atfancm mutant plants is compromised. Evidence suggests that during meiosis At-FANCM acts as antirecombinase to suppress ectopic recombination-dependent chromosome interactions, but this activity is antagonized by the ZMM pathway to enable the formation of interference-sensitive crossovers and chromosome synapsis. Surprisingly, mutation of At-FANCM overcomes the sterility phenotype of an At-MutS homolog4 mutant by apparently rescuing a proportion of crossover-designated recombination intermediates via a route that is likely At-MMS and UV sensitive81 dependent. However, this is insufficient to ensure the formation of an obligate crossover. Thus, At-FANCM is not only a safeguard for genome stability in somatic cells but is an important factor in the control of meiotic crossover formation.

Gene targeting in plants: 25 years later

“…This process has been confirmed for certain DNA helicases such as AtREC4QA or AtFANCM that are involved in the control of HR (Hartung et al, 2007;Knoll et al, 2012) and for chromatin assembly factors such as AtCAF1 (Endo et al, 2006;Kirik et al, 2006). Again, no GT experiments have been published using these mutant backgrounds.…”

Drosophila FANCM Helicase Prevents Spontaneous Mitotic Crossovers Generated by the MUS81 and SLX1 Nucleases

“…Based on immunolocalization of meiotic recombination proteins, Knoll et al (2012) hypothesized that Arabidopsis FANCM suppresses crossovers produced by MUS81, which is usually responsible for only 10-15% of meiotic crossovers in normal meiosis (Berchowitz et al 2007). In Drosophila, most 46, 18, 18, 22, 17, 23, 20, and 22.…”

“…20,30,25,28 | 16,49,20,23;MMS: 26,19 | 22,32,24,28 | 19,20;IR: 15,25,15,8 | 24,25,17,28 | 21,21,25. Statistical comparisons were done for Fancm compared to each other genotype, and Fancm Blm double mutants were compared to Blm single mutants: *P , 0.05; **P , 0.01, ***P , 0.001 (corrected for multiple comparisons; see Meiotic crossovers are elevated in some regions of the genome when FANCM is absent S. pombe Fml1 and Arabidopsis FANCM suppress crossovers during meiotic recombination (Crismani et al 2012;Knoll et al 2012;Lorenz et al 2012), and Fml1 and S. cerevisiae Mph1 suppress crossovers in vegetative cells (Sun et al 2008;Prakash et al 2009;Mazón and Symington 2013). We therefore assayed both meiotic and mitotic crossovers in Drosophila Fancm mutants.…”

High-Resolution Mapping of Crossover Events in the Hexaploid Wheat Genome Suggests a Universal Recombination Mechanism

“…However, the number of DSBs is at least 10-to 50-fold greater than the number of COs which rarely exceeds three per bivalent chromosome per meiosis (Mercier et al 2015). This paucity of COs per meiosis with regards to the number of DSBs suggests the existence of a tight control and regulation of recombination in plants that promote DSB repair in a manner that does not lead to COs. For example, the study of the two helicases AtFANCM and RECQ4 (AtRECQ4A and AtRECQ4B) (Crismani et al 2012;Knoll et al 2012;Girard et al 2014;Séguéla-Arnaud et al 2015) revealed three-and sixfold CO frequency increases in the Atfancm single mutant and the Atrecq4a/Atrecq4b double mutant, respectively, compared to the wild type. These increases result from additional COs from the class-II pathway which suggests that FANCM and RECQ4 prevent CO formation and direct recombination intermediates toward the synthesis-dependent, strandannealing, non-CO (NCO) pathway.…”