MATRILINEAL, a sperm-specific phospholipase, triggers maize haploid induction
MATRILINEAL, a sperm-specific phospholipase, triggers maize haploid induction
复制标题
DOI：
10.1038/nature20827
复制
发表时间：
2017-02-02
期刊：
影响因子：
64.8
通讯作者：
Martin, Barry
中科院分区：
文献类型：
--
作者：
Kelliher, Timothy;Starr, Dakota;Martin, Barry
开花植物的有性生殖涉及双重受精，即花粉中的两个精子与雌性胚囊中的两个性细胞的结合。现代植物育种者越来越多地寻求规避这一过程来产生双单倍体个体，这些个体源自单倍体配子体的染色体双倍细胞。加倍单倍体生产固定了近交系中的重组单倍体基因组，从而缩短了育种过程的时间(1)。许多作物都采用成本高昂的基因型依赖性组织培养方法(2)，而基于种子的体内双单倍体系统在自然界中很少见(3)，并且在育种计划中难以管理(4)。然而，价值数十亿美元的玉米杂交种子业务得到了工业化双单倍体管道的支持，该管道使用种内杂交与来自Stock 6的体内单倍体诱导雄性，首次报道于1959年（参考文献5），然后进行秋水仙碱处理。尽管使用了数十年，其作用方式仍然存在争议(6-10)。在这里，我们通过精细作图、基因组测序、遗传互补和基因编辑确定，玉米 (Zea mays) 中的单倍体诱导是由母系 (MTL)（一种花粉特异性磷脂酶）的移码突变触发的，并且 MTL 中的新编辑导致单倍体诱导率达到 6.7%（单倍体后代与总后代的百分比）。野生型 MTL 蛋白仅定位于精子细胞质，花粉 RNA 序列分析鉴定出一系列在单倍体诱导过程中过度表达的花粉特异性基因，其中一些可能介导单倍体种子的形成 (11-15)。这些发现强调了雄性配子细胞质成分对生殖成功和雄性基因组传递的重要性。鉴于 MTL 在谷物中的保守性，这一发现可能有助于开发体内单倍体诱导系统，以加速农作物的育种。
Sexual reproduction in flowering plants involves double fertilization, the union of two sperm from pollen with two sex cells in the female embryo sac. Modern plant breeders increasingly seek to circumvent this process to produce doubled haploid individuals, which derive from the chromosome-doubled cells of the haploid gametophyte. Doubled haploid production fixes recombinant haploid genomes in inbred lines, shaving years off the breeding process(1). Costly, genotype-dependent tissue culture methods are used in many crops(2), while seed-based in vivo doubled haploid systems are rare in nature(3) and difficult to manage in breeding programmes(4). The multi-billion-dollar maize hybrid seed business, however, is supported by industrial doubled haploid pipelines using intraspecific crosses to in vivo haploid inducer males derived from Stock 6, first reported in 1959 (ref. 5), followed by colchicine treatment. Despite decades of use, the mode of action remains controversial(6-10). Here we establish, through fine mapping, genome sequencing, genetic complementation, and gene editing, that haploid induction in maize (Zea mays) is triggered by a frame-shift mutation in MATRILINEAL (MTL), a pollen-specific phospholipase, and that novel edits in MTL lead to a 6.7% haploid induction rate (the percentage of haploid progeny versus total progeny). Wildtype MTL protein localizes exclusively to sperm cytoplasm, and pollen RNA-sequence profiling identifies a suite of pollen-specific genes overexpressed during haploid induction, some of which may mediate the formation of haploid seed(11-15). These findings highlight the importance of male gamete cytoplasmic components to reproductive success and male genome transmittance. Given the conservation of MTL in the cereals, this discovery may enable development of in vivo haploid induction systems to accelerate breeding in crop plants.