OsRAD17 Is Required for Meiotic Double-Strand Break Repair and Plays a Redundant Role With OsZIP4 in Synaptonemal Complex Assembly.

Qing Hu,Yi Shen,Bojun Ma,Chao Zhang,Zhukuan Cheng,Lijun Ma,Wei Liu,Zhihui Xue

doi:10.3389/fpls.2018.01236

Abstract

The repair of SPO11-dependent double-strand breaks (DSBs) by homologous recombination (HR) ensures the correct segregation of homologous chromosomes. In yeast and human, RAD17 is involved in DNA damage checkpoint control and DSB repair. However, little is known about its function in plants. In this study, we characterized the RAD17 homolog in rice. In Osrad17 pollen mother cells (PMCs), associations between non-homologous chromosomes and chromosome fragmentation were constantly observed. These aberrant chromosome associations were dependent on the formation of programmed DSBs. OsRAD17 interacts with OsRAD1 and the meiotic phenotype of Osrad1 Osrad17 is indistinguishable from the two single mutants which have similar phenotypes, manifesting they could act in the same pathway. OsZIP4, OsMSH5 and OsMER3 are members of ZMM proteins in rice that are required for crossover formation. We found that homologous pairing and synapsis, which was roughly unaffected in Oszip4 and Osrad17 single mutant, was severely disturbed in the Oszip4 Osrad17 double mutant. Similar phenotypes were observed in the Osmsh5 Osrad17 and Osmer3 Osrad1 double mutants, suggesting the cooperation between the checkpoint proteins and ZMM proteins in assuring accurate HR in rice.

Highlights

Meiotic homologous recombination (HR) is initiated by the programmed formation of DNA double-strand breaks (DSBs), which was catalyzed by SPO11, a functional homolog of subunit A of an archaeal topoisomerase (TopoVIA) (Keeney et al, 1997)
Oryza sativa RAD17 (OsRAD17) Is Required for Meiotic DSB Repair in Rice
The Osrad17 meiotic phenotype depends on programmed DSB formation, indicating the role of OsRAD17 in DSB repair

Summary

Introduction

Meiotic homologous recombination (HR) is initiated by the programmed formation of DNA double-strand breaks (DSBs), which was catalyzed by SPO11, a functional homolog of subunit A of an archaeal topoisomerase (TopoVIA) (Keeney et al, 1997). After resection by MRN/X complex (Mre11/Rad50/Xrs or Mre11/Rad50/Nbs1) and other proteins, these DSBs are processed to yield 3 overhangs (Cao et al, 1990; Ivanov et al, 1992; Nairz and Klein, 1997). With the help of RPA (Replication Protein A), the recombinases RAD51 and DMC1 are loaded to initialize homology search and strand exchange (Bishop et al, 1992; Sung and Robberson, 1995; San Filippo et al, 2008). These early steps of HR promote homologous chromosome paring and installation of the synaptonemal complex (SC) in most organisms, including plants. HR events are eventually resolved as either crossovers (COs) or noncrossovers (NCOs) in the context of the SC (Borner et al, 2004)

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Conclusion