背景回顾：Doubled haploid technology has been widely applied to multiple plant species and is recognized as one of the most important technologies for improving crop breeding efficiency. 

提出问题：Although mutations in MATRILINEAL/Zea mays PHOSPHOLIPASE A1/NOT LIKE DAD(MTL/ZmPLA1/NLD) and Zea mays DOMAIN OF UNKNOWN FUNCTION 679 MEMBRANE PROTEIN (ZmDMP) have been shown to generate haploids in maize, knowledge of the genetic basis of haploid induction (HI) remains incomplete. Therefore, cloning of new genes underlying HI is important for further elucidating its genetic architecture. 

主要发现：Here, we found that loss-of-function mutations of Zea mays PHOSPHOLIPASE D3 (ZmPLD3), one of the members from the phospholipase D subfamily, could trigger maternal HI in maize.

结果1-反向遗传学鉴定ZmPLD3：ZmPLD3 was identified through a reverse genetic strategy based on analysis of pollen-specifically expressed phospholipases, followed by validation through the clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR–Cas9) system. 

结果2-ZmPLD3突变及与MTL/ZmPLA1/NLD的协同效应：Mutations of ZmPLD3 resulted in a haploid induction rate (HIR) similar to that of mtl/zmpla1/nld and showed synergistic effects rather than functional redundancy on tripling the HIR (from 1.19% to 4.13%) in the presence of mtl/zmpla1/nld. 

结果3-RNA-seq：RNA-seq profiling of mature pollen indicated that a large number of pollen-specific differentially expressed genes were enriched in processes related to gametogenesis development, such as pollen tube development and cell communication, during the double-fertilization process. 

结果4-ZmPLD3保守性：In addition, ZmPLD3 is highly conserved among cereals, highlighting the potential application of these in vivo haploid-inducer lines for other important crop plant species. 

结论：Collectively, our discovery identifies a novel gene underlying in vivo maternal HI and provides possibility of breeding haploid inducers with further improved HIR.

 摘 要 

单倍体加倍技术被广泛用于多个植物物种中，被认为是提升作物育种改良的最重要技术之一。尽管玉米中MTL/ZmPLA1/NLD和ZmDMP基因的突变能够产生单倍体，但是对于单倍体诱导的遗传基础还不完善。因此，克隆新的单倍体诱导基因对于进一步探索该现象的遗传结构是非常重要的。本文中，作者发现玉米中磷脂酶D亚家族的ZmPLD3基因功能缺失会诱导母系单倍体形成。作者通过对花粉特异性表达的磷脂酶，再以CRISPR/Cas9基因编辑系统加以验证的反向遗传学方法鉴定到了该基因。ZmPLD3突变所导致的单倍体诱导率与mtl/zmpla1/nld类似，并且与mtl/zmpla1/nld一起的双突单倍体诱导率从1.19%增加到了4.13%，说明这两个基因在单倍体诱导方面的功能更有可能是协同的，而非功能冗余。成熟花粉的RNA-seq图谱显示，在双受精过程中花粉特异性的差异表达基因很多都富集在与配子发生相关的生物学进程上，比如花粉管发育和细胞通信等。另外，ZmPLD3基因在谷类作物中十分保守，说明其具有在其他作物中开发单倍体诱导体系的潜力。综上，本文的发现鉴定了一个新的作用于母系单倍体诱导的基因，为进一步提升单倍体诱导率提供了可能。