Abstract
Meiotic recombination is initiated from the formation of DNA double-strand breaks (DSBs). In Arabidopsis, several proteins, such as AtPRD1, AtPRD2, AtPRD3, AtDFO and topoisomerase (Topo) VI-like complex, have been identified as playing important roles in DSB formation. Topo VI-like complex in Arabidopsis may consist of subunit A (Topo VIA: AtSPO11-1 and AtSPO11-2) and subunit B (Topo VIB: MTOPVIB). Little is known about their roles in Arabidopsis DSB formation. Here, we report on the characterization of the MTOPVIB gene using the Arabidopsis mutant alleles mtopVIB-2 and mtopVIB-3, which were defective in DSB formation. mtopVIB-3 exhibited abortion in embryo sac and pollen development, leading to a significant reduction in fertility. The mtopVIB mutations affected the homologous chromosome synapsis and recombination. MTOPVIB could interact with Topo VIA proteins AtSPO11-1 and AtSPO11-2. AtPRD1 interacted directly with Topo VI–like proteins. AtPRD1 also could interact with AtPRD3 and AtDFO. The results indicated that AtPRD1 may act as a bridge protein to interact with AtPRD3 and AtDFO, and interact directly with the Topo VI-like proteins MTOPVIB, AtSPO11-1 and AtSPO11-2 to take part in DSB formation in Arabidopsis.
Highlights
In flowering plants, gametophyte formation relies on meiosis[1, 2]
Studies have shown that AtSPO11-1 and AtSPO11-2 are involved in double-strand breaks (DSBs) formation[30, 31], but how the Arabidopsis Topo VI-like complex interacts with other proteins involved in DSB formation remains unclear
Isolation of mtopVIB-3 mutant. mtopVIB-3 was identified as mt[187] in a screening of the enhancer- and gene-trap Dissociation (Ds) insertion lines in Arabidopsis ecotype Landsberg erecta (Ler)[41] by its sterility, which was not associated with the Ds insertion
Summary
Gametophyte formation relies on meiosis[1, 2]. Meiosis includes meiosis I and meiosis II. The ten proteins are organized as four interacting subcomplexes, Spo11-Ski[8], Rec102-Rec[104], Rec114-Mei4-Mer[2] and Mre11-Rad50-Xrs[29]. After its formation, the Spo11-Ski[8] subcomplex recruits Rec102-Rec[104] subcomplex to localize Spo[11] to chromatin sites and to bind to hotspots[13, 14]. Rec102-Rec[104] localizes preferentially to chromatin loops and functions as a bridge to interact with Rec114-Mei4-Mer[2] (RMM) to form a larger complex[14,15,16]. Recent findings showed that Spp[1] (a component of the COMPASS complex) can recognize and bind to H3K4me2/me[3] marks on chromatin loops to axis sites through its direct interaction with Mer[222, 23]. MEI1 encodes an unknown function protein and is meiosis-specific in DSB formation[26, 27]. Studies have shown that AtSPO11-1 and AtSPO11-2 are involved in DSB formation[30, 31], but how the Arabidopsis Topo VI-like complex interacts with other proteins involved in DSB formation remains unclear
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