EAGER: Clonal propagation of tomato through seeds

在过去的一个世纪里，杂交种子的大规模使用促成了一场农业革命。杂交作物产量高，但由于遗传分离，其后代产量不同，往往产量较低。这意味着每个季节都必须使用人工授粉等劳动密集型方法重新产生杂交种子，导致成本大幅上升。因此，杂交作物在许多作物上没有得到充分利用，特别是发展中国家的农民。最近，一种名为合成无融合生殖的技术被开发出来，使杂交水稻植株能够产生母体植物的遗传克隆种子，这样后代就可以产生与母体植物相同的高产。这种方法模拟了在许多无性植物物种中自然发生的无融合生殖过程，并利用基因组编辑和基因表达的操纵来绕过遗传分离和受精。在本项目中，将对为单子叶植物水稻开发的杂交种子的克隆繁殖方法进行改进，并将其用于双子叶植物番茄。如果在番茄上成功，这种方法可以推广到其他主要作物，如大豆和棉花，对世界农业产生相应的巨大影响。最近，通过对三个减数分裂基因的CRISPR-Cas9基因组编辑，通过消除减数分裂，然后通过婴儿潮家庭的胚胎转录因子的卵细胞表达产生的孤雌生殖，首次成功地通过有性繁殖植物在水稻中实现了克隆种子的繁殖。由此产生的种子是克隆的，并保持了亲本植物的全基因组杂合性。该项目将在双子叶植物番茄上使用类似的方法，以使杂交番茄植株能够通过种子无性系繁殖。高度保守的减数分裂基因Rec8、PAIR1和OSD1的同源基因将由CRISPR-Cas9进行基因组编辑，以消除减数分裂并形成未减少的配子。水稻和拟南芥中的胚胎因子，包括婴儿潮转录因子家族的胚胎因子，将通过与胚胎因子的同源异位表达来诱导未减数卵细胞的孤雌生殖。假定的克隆后代将通过他们的染色体倍性进行识别，并通过全基因组测序进行验证，以确认其基因组中保持父母的杂合性。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The large-scale use of hybrid seeds over the past century has contributed to a revolution in agriculture. Hybrid crop plants produce high yields, but due to genetic segregation, their progeny have variable and frequently low yields. This means that hybrid seeds have to be generated afresh for every season, using labor-intensive methods such as hand pollination, resulting in substantially higher costs. Consequently, hybrids are underutilized for many crops, especially by farmers in developing countries. Recently a technology called synthetic apomixis has been developed to enable hybrid rice plants to produce seeds that are genetic clones of the parent plant, such that the progeny can produce the same high yields as the parent plant. The method mimics a process called apomixis that occurs naturally in many asexual plant species, and utilizes genome editing together with manipulation of gene expression to bypass both genetic segregation and fertilization. In this project, the method for clonal propagation of hybrid seeds developed for the monocot plant rice will be modified and tested for use in tomato, which is a dicot species. If successful in tomato, the method can be extended to other major crops that are dicots, such as soybean and cotton, with correspondingly large impacts on world agriculture.The first successful propagation of clonal seeds by a sexually reproducing plant has been recently achieved in rice, through the elimination of meiosis by CRISPR-Cas9 genome editing of three meiotic genes, followed by parthenogenesis arising from egg cell expression of an embryogenic transcription factor of the BABY BOOM family. The resulting seeds were clonal and maintained the genome wide heterozygosity of the parent plant. A similar approach will be used in this project on the dicot plant tomato, to enable the propagation of hybrid tomato plants clonally through seeds. Tomato orthologs of the highly conserved meiosis genes REC8, PAIR1 and OSD1 will be genome edited by CRISPR-Cas9 to eliminate meiosis and form unreduced gametes. Parthenogenesis of the unreduced egg cell will be induced by ectopic expression of candidate embryogenic factors identified by orthology to embryonic factors in rice and Arabidopsis, including those of the BABY BOOM transcription factor family. Putative clonal progeny will be identified by their chromosomal ploidy, and validated by whole genome sequencing to confirm maintenance of parental heterozygosity in their genomes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.