ZmRAD17 Is Required for Accurate Double-Strand Break Repair During Maize Male Meiosis.

Ting Zhang,Yan He,Ju-Li Jing,Lei Liu

doi:10.3389/fpls.2021.626528

Abstract

RAD17, a replication factor C (RFC)-like DNA damage sensor protein, is involved in DNA checkpoint control and required for both meiosis and mitosis in yeast and mammals. In plant, the meiotic function of RAD17 was only reported in rice so far. Here, we identified and characterized the RAD17 homolog in maize. The Zmrad17 mutants exhibited normal vegetative growth but male was partially sterile. In Zmrad17 pollen mother cells, non-homologous chromosome entanglement and chromosome fragmentation were frequently observed. Immunofluorescence analysis manifested that DSB formation occurred as normal and the loading pattern of RAD51 signals was similar to wild-type at the early stage of prophase I in the mutants. The localization of the axial element ASY1 was normal, while the assembly of the central element ZYP1 was severely disrupted in Zmrad17 meiocytes. Surprisingly, no obvious defect in female sterility was observed in Zmrad17 mutants. Taken together, our results suggest that ZmRAD17 is involved in DSB repair likely by promoting synaptonemal complex assembly in maize male meiosis. These phenomena highlight a high extent of divergence from its counterpart in rice, indicating that the RAD17 dysfunction can result in a drastic dissimilarity in meiotic outcome in different plant species.

Highlights

In eukaryotes, meiosis is a key biological process for reproduction with one round of DNA replication followed by two successive cell divisions to halve chromosome number (de Massy, 2013)
To identify a putative RAD17 gene in maize, the full-length amino acid sequence of the rice RAD17 was used as a query to search in the maize genome database2 by BLASTp analysis
In the model plant Arabidopsis, the defective RAD17 was considered to have no strong effects on meiosis due to the normal fertility of both male and female, whereas the mutant displayed hypersensitive to DNA-damaging agents with the frequent presence of intrachromosomal homologous recombination (HR) during mitosis (Heitzeberg et al, 2004)

Summary

Introduction

Meiosis is a key biological process for reproduction with one round of DNA replication followed by two successive cell divisions (meiosis I and II) to halve chromosome number (de Massy, 2013). During meiosis I, homologous pairing and synapsis promote crossover (CO) formation, guaranteeing the accurate segregation of homologous chromosomes (Mercier et al, 2015). This division is called as reductional division (Ma, 2006). RPA is replaced by the RecA recombinases RAD51 and DMC1 forming nucleoprotein filaments and promoting homology search and single strand invasion to produce recombination intermediates called as the displacement (D)-loop (Hunter and Kleckner, 2001; Cloud et al, 2012). The extended D-Loop gives rise to double Holliday Junction (dHJ), which is resolved into a minority of COs and large number of NCOs (Youds and Boulton, 2011; Pyatnitskaya et al, 2019)

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Results

Conclusion