Mutation of ZmDMP enhances haploid induction in maize

First author: Yu Zhong; Affiliations: China Agricultural University (中国农业大学): Beijing, China

Corresponding author: Shaojiang Chen 

Doubled haploid (DH) breeding based on in vivo haploid induction has led to a new approach for maize breeding. All modern haploid inducers used in DH breeding are derived from the haploid inducer line Stock6. Two key quantitative trait loci, qhir1 and qhir8, lead to high-frequency haploid induction. Mutation of the gene MTL/ZmPLA1/NLD in qhir1 could generate a ~2% haploid induction rate (HIR); nevertheless, this mutation is insufficient for modern haploid inducers whose average HIR is ~10%. Therefore, cloning of the gene underlying qhir8 is important for illuminating the genetic basis of haploid induction. Here, we present the discovery that mutation of a non-Stock6-originating gene in qhir8, namely, ZmDMP, enhances and triggers haploid induction. ZmDMP was identified by map-based cloning and further verified by CRISPR–Cas9-mediated knockout experiments. A single-nucleotide change in ZmDMP leads to a 2–3-fold increase in the HIR. ZmDMP knockout triggered haploid induction with a HIR of 0.1–0.3% and exhibited a greater ability to increase the HIR by 5–6-fold in the presence of mtl/zmpla1/nld. ZmDMP was highly expressed during the late stage of pollen development and localized to the plasma membrane. These findings provide important approaches for studying the molecular mechanism of haploid induction and improving DH breeding efficiency in maize.

通过体内单倍体诱导进行的单倍体加倍（Doubled haploid，DH）育种为玉米的育种改良开拓了一个新的方法。所有现在使用的单倍体诱导剂都源自于单倍体诱导株系Stock6。两个关键的数量性状位点qhir1和qhir8能够导致高频的单倍体诱导。在qhir1株系中突变MTL/ZmPLA1/NLD基因能够产生大约2%的单倍体诱导率（haploid induction rate，HIR），然而，该突变并不足以与现代单倍体诱导剂10%的HIR相提并论。因此，克隆qhir8潜在的功能基因对于理解单倍体诱导的遗传基础是非常重要的。本文中，作者发现了在qhir8中突变一个不是来自Stock6的基因ZmDMP能够增强单倍体诱导。作者通过图位克隆鉴定到了ZmDMP基因，并进一步通过CRISPR–Cas9介导的基因敲除技术验证了该基因的功能。在ZmDMP基因上一个特定核苷酸的改变能够提升2-3倍的HIR。ZmDMP敲除诱导的单倍体产率为0.1–0.3%，并且通过同时突变mtl/zmpla1/nld基因能够将HIR增加5-6倍。ZmDMP基因在花粉发育的后期高表达，并且定位于质膜上。本文的发现揭示了单倍体诱导的分子机制，并为提升玉米的DH育种效率提供了新的方法。

通讯：陈绍江 (http://cab.cau.edu.cn/art/2017/6/9/art_27217_44.html)

个人简介：1979-1983年，河南农业大学，学士；1985-1988年，河南农业大学，硕士；1992-1995年，东北农业大学，博士；1995-1997年，中国农业大学，博士后。

研究方向：玉米单倍体育种技术，高油与青贮玉米育种、玉米生殖生物学，工程化作物育种等。

doi: https://doi.org/10.1038/s41477-019-0443-7

Journal: Nature Plants

Published date: June 10, 2019