The Role of ZIP4 in Homologous Chromosome Synapsis and Crossover Formation in Rice Meiosis

Abstract

SummaryIn budding yeast, the ZMM complex is closely associated with class I crossovers and synaptonemal complex (SC) formation. However, the relationship between the ZMM genes remains unclear in most higher eukaryotes. Here, we identify the rice ZIP4 homolog, a member of the ZMM gene group, and explore its relationship with two other characterized ZMM genes, MER3 and ZEP1. Our results show that in the rice zip4 mutant, the chiasma frequency is greatly reduced, although synapsis proceeds with only mild defects. Immunocytological analyses of wild-type rice reveal that ZIP4 presents as punctuate foci and colocalizes with MER3 in prophase I meiocytes. Additionally, ZIP4 is essential for the loading of MER3 onto chromosomes, but not vice versa. Double-mutant analyses show that zip4 mer3 displays a greater decrease in the mean number of chiasmata than either of the zip4 or mer3 single mutants, suggesting that ZIP4 and MER3 work cooperatively to promote CO formation but their individual contributions are not completely identical in rice. Although zep1 alone gives an increased chiasma number, both zip4 zep1 and mer3 zep1 show a much lower chiasma number than the zip4 or mer3 single mutants. These results imply that the normal functions of ZIP4 and MER3 are required for the regulation of COs by ZEP1.

The F-Box Protein ZYGO1 Mediates Bouquet Formation to Promote Homologous Pairing, Synapsis, and Recombination in Rice Meiosis

“…No significant difference in gH2AX signals was observed between meiocytes of zygo1 and the wild type at early prophase I ( Figures 5A and 5B), suggesting that the initiation of homologous recombination was not disturbed in zygo1. We also investigated the localizations of OsCOM1, OsDMC1, and OsZIP4, which are all essential elements involved in rice DSB repair (Ji et al, 2012;Shen et al, 2012;Wang et al, 2016). In the wild type, the signals of OsCOM1, OsDMC1, and OsZIP4 were observed as punctuate foci at zygotene.…”

“…The zygo1-3 mutant allele was used for data generation throughout our research. The pair1, Oscom1, Oszip4, and hei10 mutants used in this study were reported previously (Ji et al, 2012;Shen et al, 2012;Wang et al, 2012;Che et al, 2014). The japonica rice variety Yandao 8 was used for wild-type analysis.…”

“…The primary antibodies against OsREC8, PAIR2, PAIR3, g-H2AX, OsCOM1, OsDMC1, OsZIP4, and HEI10 were previously reported (Wang et al, 2011Ji et al, 2012;Shen et al, 2012;Wang et al, 2016). The guinea pig antibody against ZEP1 was generated with the ZEP1 fusion protein (amino acids 426-612) based on the report of the mouse antibody against ZEP1 (Wang et al, 2010).…”

Crossover Formation During Rice Meiosis Relies on Interaction of OsMSH4 and OsMSH5

“…Besides, the number of chiasmata per cell in Osmsh5 was also decreased to 10% of the wild type (Luo et al 2013). The reduction in Osmsh4 and Osmsh5 was much greater than the other zmm mutants in rice, such as Oszip4 and Osmer3, which affected the formation of 70-80% of COs, leaving 30% chiasmata in the mutants (Wang et al 2009Shen et al 2012). Considering these results, we suggest that OsMSH4 in association with OsMSH5 plays a far more crucial role in the formation of COs than other ZMM proteins.…”

Replication Protein A2c Coupled with Replication Protein A1c Regulates Crossover Formation during Meiosis in Rice

“…There was a slight but significant reduction in COs in ZYP1 RNAi and an increased number of COs in zep1 (Higgins et al, 2005;Osman et al, 2006;Wang et al, 2010). However, zep1 zip4 and zep1 mer3 double mutants exhibited much lower numbers of COs than zip4 and mer3 single mutants (Chen et al, 2005;Mercier et al, 2005;Wang et al, 2009;Shen et al, 2012). Recently, a homolog of yeast Zip3, Human Enhancer of Invasion10 (HEI10), was identified in both Arabidopsis and rice.…”