Concurrent Disruption of Genetic Interference and Increase of Genetic Recombination Frequency in Hybrid Rice Using CRISPR/Cas9.

Chaolei Liu,Yufeng Hua,Tingting Sun,Xin Wei,Qing Liu,Jianrong Lin,Kejian Wang,Mingguo Wu,Zhukuan Cheng,Guijie Du,Yiwei Cao

doi:10.3389/fpls.2021.757152

Abstract

Manipulation of the distribution and frequency of meiotic recombination events to increase genetic diversity and disrupting genetic interference are long-standing goals in crop breeding. However, attenuation of genetic interference is usually accompanied by a reduction in recombination frequency and subsequent loss of plant fertility. In the present study, we generated null mutants of the ZEP1 gene, which encodes the central component of the meiotic synaptonemal complex (SC), in a hybrid rice using CRISPR/Cas9. The null mutants exhibited absolute male sterility but maintained nearly unaffected female fertility. By pollinating the zep1 null mutants with pollen from indica rice variety 93-11, we successfully conducted genetic analysis and found that genetic recombination frequency was greatly increased and genetic interference was completely eliminated in the absence of ZEP1. The findings provided direct evidence to support the controversial hypothesis that SC is involved in mediating interference. Additionally, the remained female fertility of the null mutants makes it possible to break linkage drag. Our study provides a potential approach to increase genetic diversity and fully eliminate genetic interference in rice breeding.

Highlights

Plant breeding aims to develop superior varieties to suit the needs of farmers and consumers (Moose and Mumm, 2008)
We revealed that genetic interference is completely eliminated in the absence of ZEP1, indicating an important role of synaptonemal complex (SC) in mediating interference in rice
The Tos17 insertion mutant lines of ZEP1 used in previous studies are partial lossof-function mutants (Wang et al, 2010; Wang K. et al, 2015), which still contain the N-terminal residues

Summary

Introduction

Plant breeding aims to develop superior varieties to suit the needs of farmers and consumers (Moose and Mumm, 2008). Innovations in breeding materials strongly depend on creating novel allele combinations that bring together advantageous alleles and remove linked, disadvantageous alleles. This is traditionally limited by the number of crossovers (COs) during meiosis (Taagen et al, 2020). To generate sufficient genetic diversity, breeders and geneticists are exploring approaches to increase the CO frequency, alter CO distribution, or induce COs between non-homologous chromosomal regions (Mieulet et al, 2018; Blary and Jenczewski, 2019). The synaptonemal complex (SC) is a meiosis-specific structure involved in CO formation and chromosome segregation (Gao and Colaiácovo, 2018). SC assembly starts from early prophase I and forms a tripartite structure at pachytene, which consists of axial or lateral

Methods

Results

Conclusion